DIYstompboxes.com

This is one of my design/hacks. The Bearhug is a tonally transparent, ultra-quiet, tiny, and easy-to-build compressor. It occupies some middle ground between the ultra-subtle compressors like the Flatline/Afterlife and Orange Squeezer and the super squishy compressors like the Ross.

Here is the build document from Josh at 1776 Effects (includes the etch):
https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bear%20Hug%20BOM.pdf

There will be a PCB run release by 1776 Effects sometime around the New Year.

Some background

Compressors are one of my favorite effects -- I've used an Orange Squeezer as an "always on" pedal in my rig for years now. I've built a lot of different compressors now, and there are a large number of good or great designs out there. I wasn't so much looking to improve on a great design as to find a little bit of unused or underused turf in the DIY community.

I had been talking with Ray Ring (Circuit Salad is his website) recently after building his compressor, which uses an opto-FET, and he mentioned the phrase "linearized FET" as one way to create compression. The use of a linearized FET frees up some interesting design space. It allows anything from a very, very tiny amount of compression to ...well, more attenuation than you'll ever need. And they're faster than an optical design -- the attack can be as little as a few milliseconds. While looking over lots and lots of different compressor schematics, I recognized the use of a linearized FET in the Rothwell Lovesqueeze. I built it and liked it, but wanted to change a few things, such as improving how it reacted to the guitar's volume and the input impedance, and getting better separation between the compression and audio levels.

Here's what I ended up with:
Josh McClarren (Gtr2/1776Effects) drew this version of the schematic.
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bear%20Hug%20Schematic.png)
My schematic (with notes and mods): https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20compressor%20schematic.pdf

What it sounds like:


(I recommend watching in Youtube because the annotations don't show up properly in the embedded version.)

My goals with this design:

1) It had to be easy to build. So no weird resistor values or uncommon capacitors. No difficult to find or unobtainable parts. Pretty much part has a workable substitution even though they're all common. As a side benefit, it's dirt cheap. The entire circuit cost me around $7 including the 9mm pots.

2) No weird biasing or other issues that make it difficult for someone to tell if the effect is working properly. As much as I love Orange Squeezers, if the builder doesn't know what it's supposed to do or sound like, they won't bias it correctly and then it just works as a boost. I wanted to avoid this.

3) It had to be quiet. These days, honestly, if your compressor design hisses and buzzes like a Ross/Dynacomp, it's time to go back to the drawing board. I'm ridiculously happy that I succeeded with this one. This circuit is completely silent -- there's no circuit noise at all, and the high signal-to-noise ratio is identical at all compression settings. (You'll bring up the noise floor when running it as a boost, but it's not contributing any noise -- just amplifying the pickup's hum and your guitar signal with it.)

4) I wanted it small enough to fit in a 1590A. Check!

How it works

The audio path is a MOSFET booster (basically Jack Orman's with a couple adjustments) -- this gave the effect enough output to still work as a boost, but it's super quiet and has extremely high input impedance. There are a few changes to accommodate the diode voltage drop at the 9v input, and I used a negative feedback cap (C4) to cut radio frequencies rather than a cap to ground, but this is all standard stuff.

Tonally, this circuit neither cuts nor boosts any guitar frequencies. The input and output caps are sufficient for the tonal frequency of at least a 4-string bass (I don't have a 5-string to test on). C4 can be adjusted to add or cut some overall available brightness (I used 47pF in my build because, say it with me, "Jon likes his treble").

The output volume will be at unity right around noon. The highest setting will be boosted by ~10-15 dB, depending on a handful of tolerances.

There is no tone control in this design, but if you really want one, the best choice is AMZ's version 2 of Mark Hammer's Stupidly Wonderful Tone Control.

The compression path works like this: Your signal is tapped at the collector of Q1, where it is amplified like crazy by a high gain transistor. The comp knob sets the gain within a fairly small range (500R, with a 47R minimum). Your signal is then peak-to-peak rectified (essentially the rectifier circuit from the Lovesqueeze; apparently it's a fairly standard method), and a negative voltage swing of anywhere from about -.2v to -2v is produced at C9, with the size of the swing depending on the size of the signal after it was amplified by Q2. The negative voltage swing then drives up the resistance on the FET (Q3), which at last is connected to the emitter of Q1 through a 47uF cap. The FET's default in this setup is completely on. The resistance of a 2N5457 is only ~300Ohms, so this sets the gain of the Q1 stage a safe distance above the distortion point but still "pretty darned loud." When your input signal drives up the resistance (typically anywhere from about 100 Ohms on the lowest settings to as much as 2K with the highest settings with a really, really hard strum), that lowers the gain of the MOSFET stage, thus decreasing your guitar signal's volume and creating compression. Whew!

C9 is a hold cap, fairly small as hold caps go so that we can get subtle settings. The decay of the cap is set by a parallel resistor; here, we've used a pair in series and a High/Low switch (Sw1) that bypasses the larger resistor, giving us two decay levels. When the switch is on ("Low"), the 10K gives an extremely fast decay -- basically, it will stop compressing immediately after it stops receiving a signal. This makes it work more like peak limiting. When the switch is off ("High"), the added resistance slows down the decay, increasing the total amount of compression available and adding a "duck and swell" effect at the highest settings. 47K is the nominal setting -- the maximum "Low" setting will be about equivalent to the minimum "High" setting -- but 100K may be used for a more dramatic change between Low and High modes.

Here's my perf layout ...
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20layout.png)
PDF: https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20layout.pdf

And an etch layout from Josh!
(https://dl.dropbox.com/u/9878279/Jon%20Patton%27s%20layouts/Bearhug%20etch%20layout.jpg)
(The etchable image is in the build doc above.)

And here's my build, 1590A on perfboard:
(http://jonpattonmusic.files.wordpress.com/2012/10/bearhug-compressor.jpg?h=350)(http://jonpattonmusic.files.wordpress.com/2012/10/bearhug-guts.jpg?h=350)

Credit where credit is due: This circuit design uses some elements from the Lovesqueeze and Jack Orman's (AMZ) Mosfet booster. Mark Hammer and PRR helped me understand the rectifier. Joshua McClarren (Gtr2/1776 Effects) designed the etch and PCB layouts. Extra props to R O Tyree for his help in understanding compressors in general.

Awesome. Been looking for a subtle, low part count, quiet comp to use as input for overdrives.

Have you tried different 2N5457s? Wondering if the manufacture variations of that part cause problems.

Looks cool!

How it compares to a "real" compressor/limiter? Or maybe i should ask it this way: what is the value of the fixed settings? (attack, ratio)

From your post it seems like that the attack is really fast and the release can be really fast (more limiter like) or slower. (more compressor like) I guess the pot marked as Comp is a thresh
hold pot. What about the ratio? Is it high/infinite (limiter like) or low (like compressors)?

Can i use different germanium diodes? (I have 1N34As)

The reason i am asking because i'd like to have this configured as a clean sounding limiter (fast attack, fast release, high/infinite ratio) and build an other compressor with more pots for the usual guitar stuff (like raising sustain etc.)

Nice!  I like your circuits.
yes compression is hard to hear on youtube, but the amount of noise in your vids is making it even harder..sounds like you're in the shower with the water running  :icon_lol:

Quote from: WhenBoredomPeaks on November 08, 2012, 08:19:10 AM
Looks cool!

How it compares to a "real" compressor/limiter? Or maybe i should ask it this way: what is the value of the fixed settings? (attack, ratio)

From your post it seems like that the attack is really fast and the release can be really fast (more limiter like) or slower. (more compressor like) I guess the pot marked as Comp is a thresh
hold pot. What about the ratio? Is it high/infinite (limiter like) or low (like compressors)?

Can i use different germanium diodes? (I have 1N34As)

The reason i am asking because i'd like to have this configured as a clean sounding limiter (fast attack, fast release, high/infinite ratio) and build an other compressor with more pots for the usual guitar stuff (like raising sustain etc.)

I don't have a spectroscope, so I can't give you exact numbers on something like the ratio. I can explain how it works for the most part, though.

-The ratio can be very high depending on the size of the input signal. There's no true infinite ratio design in a stompbox (nor, I think, in analog compressors, period), but a FET's maximum resistance is, what, 300M? You're need an infinitely large input signal to get there. If I had to guess based on other compressors I have lying around (lots!), I'd say that the ratio must be lower than 10:1, probably more like 5:1. Turning up the comp knob does lower the threshold, but it also in part controls the ratio: because if you turn down the gain of Q2, it won't amplify the signal as much going into the rectifier, and the decay characteristics will take care of keeping the FET's resistance from just increasing forever.

-The attack is set by the way the rectifier works: a negative wave cycle generates the negative voltage. The attack is anywhere from .5 to 1.5 cycles. That's still absurdly fast for any stompbox compressor, 10mS or less. PRR's explanation is:

"If your first transient is positive, nothing happens on that half-cycle. For a simple SIN wave, action is delayed almost 1.5 half-cycles from the start of the SIN, 1 half-cycle from the first (positive) peak."

-The decay, as noted, is set by the values of R9/R10 and C9. I believe it's ~47ms on the low decay setting and ~220ms on the high decay setting at max Comp settings.

-You can use 1N34A and it'll be okay, but that's needlessly expensive. It also might compress a little more overall, but you can just turn down the comp pot if that happens. BAT41 or 1N270 would be better if you just can't get 1N60P. However, 1N60P (Fv ~ .25) is a silicon work-alike of the 1N60, and chosen because they only cost 2c each and are available from dozens of sources: Ebay, Mouser, Taydam, etc. etc. They're the cheapest diode with Fv under .3 and they have a tight tolerance. I use them in many different circuits requiring schotkeys and germaniums.

Hopefully that's all your questions.

Quote from: Kesh on November 08, 2012, 04:57:00 AM
Awesome. Been looking for a subtle, low part count, quiet comp to use as input for overdrives.

Have you tried different 2N5457s? Wondering if the manufacture variations of that part cause problems.

I'm pretty sure it would have to be wildly out of spec, to the point of being broken, for it not to work. I test pretty much every FET I get, and I've never had a 2N5457 that was far enough off of the bell curve to be able to say what might happen. This has been built multiple times with no consideration given to the individual FET's specs and it has worked exactly the same each time. This isn't a biasing situation, which is where FETs can sometimes cause problems. :)

Quote from: ~arph on November 08, 2012, 08:22:09 AM
Nice!  I like your circuits.
yes compression is hard to hear on youtube, but the amount of noise in your vids is making it even harder..sounds like you're in the shower with the water running  :icon_lol:

Sorry! It was in the middle of a hurricane! That was the only free time I really had to get it filmed. :P

NICE JOB!  ;)

Sounds great- solid approach and very importantly - an efficient, and clean design.

very cool

How well can it handle peaks?  I play a high output bass and most pedal compressors are too squishy for me.

Dirt boxes sound too compressed sometimes so I'm looking for a compressor/ limiter project.

Quote from: Bill Mountain on November 08, 2012, 04:30:24 PM
How well can it handle peaks?  I play a high output bass and most pedal compressors are too squishy for me.

Dirt boxes sound too compressed sometimes so I'm looking for a compressor/ limiter project.

The lowest comp settings have an pretty high threshold. A strat barely triggers it except with a very hard strum. I'd say almost any setting on 10K decay would be fine for active pickups as shown, but if the minimum setting is too much, any change that lowers the gain of Q2 will also raise the threshold and reduce the total compression available. This includes simply omitting R12, which would leave open the possibility of still using it with a passive guitar or bass.

I don't have an active bass, so I can't tell you for absolutely certain -- I had to use a boost to see how it handled anything hotter than a broadcaster (which is pretty hot but not on the level of a Firebird or EMGs). It handled it well enough that I was confident that 547R was the right value for the comp pot. It only takes maybe 10 minutes to breadboard, and I'd be interesting in knowing if it CAN handle actives and still stay subtle.

I can say that it doesn't cut any bass freqs. :)

I've got everything except the 1k pot and the zener.  I'll have to use generic Ge's and a 2N5458 but that shouldn't be a problem.  Any benefits to discrete over IC's like the Rothwell.

Josh at 1776 Effects got the PCBs in today!

Here's the link if anyone is interested and doesn't etch or build on perfboard:
http://1776effects.com/store/

The build document on his site also contains the etch image (same as the document in my top post).

Quote from: Bill Mountain on November 08, 2012, 04:55:07 PM
I've got everything except the 1k pot and the zener.  I'll have to use generic Ge's and a 2N5458 but that shouldn't be a problem.

Hi, Bill, sorry I never saw your questions. The 5458 and any generic Ge will both work, though the 1N60P was chosen because it's ridiculously cheap. The 5457 seemed a little more responsive (I tried both).

Quote from: Bill Mountain on November 08, 2012, 04:55:07 PMAny benefits to discrete over IC's like the Rothwell.

Mostly it's a flavor thing. I don't really claim that this is better than something like the Rothwell, just that it's another way of doing something similar. I think it has its good points, however.

The BS170 has a little bit of its own compression. I really liked the super high input impedance. It meant fewer capacitors/filtering and fewer parts in general. The MOSFET audio stage has a little less noise than the op amp in the Rothwell. Although I didn't really run into distortion with either one, theoretically, the Rothwell could distort with a boosted input signal at max compression on the front end of the note (the gain pot in the Rothwell is limited to 5K because any higher and it distorts). Not that distortion is desirable in any compressor, but at least if someone does manage to overdrive the audio path in a MOSFET (I couldn't with this ... 300Ohms on the source is a lot), the MOSFET's distortion sounds nicer. Finally, it's a little more modular, since there are multiple substitutions that work for most of the parts, and transistor stages always seem to be a little more tweakable than op amp stages. With an op amp design, you can't do something weird like ... stick a germanium transistor in the audio stage and turn it into an overdrive with sag ... (... this just occurred to me and now I need to go try it)

I know some people prefer working with op amps; I prefer to work with transistors.

Obviously one huge disadvantage is that the parts are either obsolete or getting there. I don't think there's a SMD version of the 5457, right?

Ordered! I'm looking forward to this :)

Quote from: bean on December 07, 2012, 10:50:42 PM
Ordered! I'm looking forward to this :)

:o

Cool! One question, though: C9 looks backwards to me, and the notes in one of your links refer to it as "reversed." What's with that?

Negative voltage from the signal (filtered out by the 1n60p rectifierdiodes) controls the fet; so with respect to ground the polarity of this cap is correct.

Nice design Jon! Will try it soon.
Maarten

Ah, I see now. I was neglecting C7 & C8, the DC blocking caps. Thank you.

Hey, if anyone's interested, 1776 Effects current has the PCBs for this design discounted to $6. Just in case anyone was on the fence about building it. :D

I posted this in the Pictures thread a while back:

Quote from: bluebunny on July 13, 2013, 02:01:01 PM
Today's offerings:

(http://www.bouron.org.uk/marc/bh234.JPG)

(http://www.bouron.org.uk/marc/bh235.JPG)

Jon's Bearhug (http://www.diystompboxes.com/smfforum/index.php?topic=99892.msg876953#msg876953) compressor, on my Vero layout (http://www.bouron.org.uk/marc/BHUGDIY.GIF).

Then Jon said this:

Quote from: midwayfair on July 14, 2013, 10:30:33 AM
Aww, that's an adorable graphic. :) Thanks for building it. Hope you like it!

And I replied:

Quote from: bluebunny on July 15, 2013, 08:20:30 AM
It is indeed very cute.  It was a pleasure building it - thanks for sharing with us, Jon - but it doesn't quite work yet!   :-[   It's a great little distortion pedal, but not so good as a compressor just yet.  Most likely self-inflicted...   :D  Need to do a little debugging...

And Jon added:

Quote from: midwayfair on July 15, 2013, 09:25:18 AM
Start a debug thread and I'll help you out. :)

And I said:

Quote from: bluebunny on July 16, 2013, 08:48:37 AM
Thanks Jon - will do.  Just want to go over my homebrew Vero layout first.  I'm hoping it's something obvious and stooopid.  Otherwise, a debug thread is on its way!

Edit: found a bug in my Vero layout - missing track cut!   :icon_rolleyes:   Will fix when I get a chance and report back...

Well, long story short - the missing track cut was indeed the culprit - all fixed now!  This is a great little compressor.  And cute.   ;)  Thanks again to Jon for sharing with us.

Glad you got yours working! :)

Thanks Jon.  Yeah, I'm pleased too.  I like your design a lot and the results are great.  Very quiet and gets the job done nicely.  I'll be trying it out on my bass next.

I was tinkering with the Bearhug and wanted to see if I couldn't maybe get a wee bit more out of it. I found that making it compress more revealed a bit of a limitation in the attack, and further limitations when placed after an overdrive.

Anyway, these values will make it more a traditional compressor and less of just a 'boost with compression.' Most of the same sounds should still be in there, but you won't be getting above unity volume while compressing at max compression. (Of course, you can just turn down the compression.)

If you're happy with your build, there's probably no reason to change it, but if you weren't happy, you might try these mods. This won't make it a different pedal, just make the comp control have a much wider range.

Changes:
R14: 100R-100k. This is the only change I think is essential, and leaving it at 1M was really a design flaw on my part, since it seems to increases the attack time enough that the low setting was doing too little on all but the highest threshold settings. There's not much difference between these values, just whatever you have on hand. This change also makes the low Fv diode choice a little less critical.

Remove R12. This gives you back the mild/boost settings. I'd also recommend a  reverse log for the comp control if you have one. This will keep it from bunching up.

Optional changes:
R4: increase to 4.7k. This boosts the output of q1, and I've suggested it on enough tech help threads that I think I should just make it standard. You can go higher, but there shouldn't be a need unless you use really low output pickups.

R3: I've been making this 4.7k on some builds, but I don't think it's really necessary with the R14 change, again unless you have low output pickups and you need a 'kill' setting.

All part numbers are on the 1776 schematic.

Summary of changes:
-Change R4 to 4.7K (should bias to ~5V)
-Remove R12
-Change R14 to 1K
-Use generic silicon diodes for D2 and D3.
-Use a 1KC for the comp pot to keep it from bunching up (because R12 was removed)
-Optional (for low-output pickups): Change R3 to 4.7K.

Why these changes are good:
-More reliable compression with a wider range of pickups
-Smoother sound overall.
-Slightly more output/boost
-Er ... a few cents cheaper to make!

Okay, I promised Josh a slightly more thorough round of testing and explanation before he adds this to the build doc.

I built a couple boards yesterday to test against my old stock version and did an a/b/c as soon as I got back from work.

Version A - old stock version.

Really only worked when it was just barely turning on. With my single coils, this was pretty much at the top of the compression range. It felt stiff. Also, the total output was less than the other versions here, even with the same perceived amount of compression. I felt like this had only one setting that worked with any given guitar, and that setting was never one that offered anything other than just a touch of compression.

Version B
This is on my development board, which has sockets for All The Things -- I set that up as described yesterday with all four mods (and R14 = 100R) to get the maximum squishiness.

This was the opposite. I felt like it was simply TOO easy to trigger. This meant that my minibuckers were sounding best at 0 or 9:00 on the Comp knob. It just felt too rubbery and extreme. Adjusting R3 back down to 2.2K or even lower really didn't back things off quite enough to use it as an almost pure boost. Max compression settings were essentially useless: it would compress even softly played notes down to unity volume, but because the decay is short it sounded like breathing. Ripple also became noticeable with higher output pickups. I can't imagine any pickups being weak enough to need these settings.

Since I had sockets, I tried a few different things and ended up with version C ...

Version C - new version
R14: 1K, removed R12, R4 = 4.7K (biases to ~5V), 1N4148 diodes (these could be 1N4001 or whatever).

This works out as a nice compromise. It has a sweet spot with my single coils between 3:00 and max, where it sounds very natural most of the time, and it's able to get above unity volume at any setting. The output is much higher than A overall with the comp backed off but it's still compressing even on the lowest settings with single coils. With humbuckers, it turned on reliably closer to noon but never felt out of control.

The nice thing about doing it this way is that if you WANT the squashed settings, there's room to go upward with minimal changes: increase R3 or even put the Schottky diodes back in.

-------------

Okay, so what's the deal with R14 and why was it 1M in the first version?

I've mentioned that the linearized FET set-up in Bearhug (everything between Q2 and Q3) was lifted wholesale from the Rothwell Lovesqueeze. Apparently, in the Lovesqueeze, the equivalent resistor to R14 is needed because it forms a voltage divider with the equivalent of R8 to split between the audio and control voltage.

In the Bearhug, that's unnecessary. The rectifier is fully decoupled from the audio path and no noise bleeds in. All it's doing is blocking the voltage needed to drive the FET reliably.

---------------
While I'm here ... some mods

-Hey! Anyone want a third "even longer" decay setting?
Use a SPDT on-off-on. Wire a 220K to lugs 1 and 3. Replace R10 with a larger resistor, 220K (for a 1s decay). Wire the switch as normal. In the center, R9 and our new R10 are in the circuit all the time = long decay. Flipped so that lugs 1 and 2 are connected, R10 is bypassed (normal short setting). Flipped so that lugs 2 and 3 are connected, a 220K resistor is put in parallel with R10, giving 110K total, for a decay of ~500ms, which is almost the same as our old "long" setting. Is this useful? I dunno. Might be for some people and it's very easy to do!

-I think how I did the emitter on Q2 was unnecessarily complicated. I set it up as if it were another MOSFET driving that stage, but ended up using a BJT because they're cheaper and the transistor characteristics didn't matter much. You could jumper C10 and leave off R13 if you wanted to save a couple parts.

Hi, thanks for your posts/design. I'll built it soon :-) and let you know.
I like trx design too!

Putting a resistor (or a pot) after C8, just before the diodes, should set the attack (charging time of C9).

For C9 have you tried the tantalum ones ?

Quote from: Mbas974 on August 14, 2013, 04:52:52 PM
Hi, thanks for your posts/design. I'll built it soon :-) and let you know.
I like trx design too!

Putting a resistor (or a pot) after C8, just before the diodes, should set the attack (charging time of C9).

For C9 have you tried the tantalum ones ?

I don't think the composition of c9 is important. Any internal resistance differences will be negated by the resistor that's in parallel.

And yes, you could add an attack mod, but I prefer a near- instantaneous attack here, especially since the decay in one mode is so short and the decay isn't very long. If you use a 1k or so, it'll feel more like an Orange Squeezer I think.

could i use a 2n5088 in the place of the mpsa18 Jon? please

Quote from: Kipper4 on August 15, 2013, 10:51:29 AM
could i use a 2n5088 in the place of the mpsa18 Jon? please

Yes, any medium-high gain transistor is fine there, and I suppose there was no real reason for me to specify MPSA18 when a 3904 would have worked with a slightly higher R3 and made the project cheaper.

2N5089 would be slightly closer in the gain range of the MPSA18, but it shouldn't make too big of a difference. You can always bump up R3 a little if you need to.

i'm certain i have a few 89's in.
Thanks for the quick response
Rich

Right now i'm confused with comparing the layout to the schematic
R4 appears as 2k2 in the BOM and schematic but as 4k7 in the layout correct?
Also i cant figure out how the top left hand corner is wired
ie junction of c2,c4 ,d2 goes to BS170 gate?
ie junction of C4 C6 C5 go to the drain

i cant for the life of me figure out how its wired underneath on the perflayout which btw i just used to build this
thanks for any help Jon
Right now its buzzing and beyond low volume.
time to get the dmm out and put it on buzzer.

Quote from: Kipper4 on August 15, 2013, 02:59:36 PM
Right now i'm confused with comparing the layout to the schematic
R4 appears as 2k2 in the BOM and schematic but as 4k7 in the layout correct?
Also i cant figure out how the top left hand corner is wired
ie junction of c2,c4 ,d2 goes to BS170 gate?
ie junction of C4 C6 C5 go to the drain

i cant for the life of me figure out how its wired underneath on the perflayout which btw i just used to build this
thanks for any help Jon
Right now its buzzing and beyond low volume.
time to get the dmm out and put it on buzzer.

Which BOM are you using? The BOM in Josh's document is correct, but the schematic still has the old values. (I'd update the schematic, but I don't have the eagle file it was created from.)

The connections on the schematic are all still correct, but a couple values are different. The values have all been updated on the layout. R4 = 4.7K now (it's the only 4.7K in the schematic).

Moving from left to right:
Gate connections: The 1uF input cap (C1), the 10M resistor connected to Vb (R2), the Zener's cathode (D2), and one leg of the 100pF cap (C4) are connected to the gate.

Drain connections: 100pF cap (C4), 4.7K resistor connected to Va (R3), 10uF output cap (C6), and 10nF cap that goes to the rectifier (C5).

The other connections in the top left:
10uF cap from Vb to ground.
100K from Vb to ground.

(Vb is the bias voltage created by the 100K/100K voltage divider)

Take some voltages, and post pics of both sides of the board. If you used a socket, you might want to pull Q2 and focus on getting the MOSFET booster half of it working first, since it's the really simple part of the circuit.

its almost certainly the mosfet booster thats the problem.
I dont know much about transistor voltages but i know this feels wrong

wallwart voltage when connected to circuit 8.7

Q1
D8.15
S 0
G 0

Q2
C 7.41
B 0.61
E 0.36

Q3
D 0
S 0
G 0.63

i'll take some pics in a minute

Vb is 5.46v btw

i think i have it wired right now but after about 15 seconds it loses all the volume and only works when i unplug it and reconnect it.
and it hums bad too.
i'll be back tommorow evening now its getting past my bed time.

new voltages
Q1
D 3018
G 0.92
S 3.1

Q2
C 7.74
B 0.63
E 0.39

Q3
G 0.63
S 0
D 0


WALLWART CONNECTED 9.2V
vb 5.8v

Quote from: Kipper4 on August 15, 2013, 04:47:32 PM
new voltages
Q1
D 3018
G 0.92
S 3.1

Source is too high. double check around there.

My internet is really spotty this afternoon, I might not be around to help. There's a bunch of general troubleshooting tips in the Madbean thread for this circuit. If I have a better connection tonight I'll come back and help more.

I neglected to mention I used 1n60 diodes too

Can I also just say don't worry tonight I should be asleep by now so ill debug it tomorrow night. I really appreciate your help john

Quick question.  I'm relatively new to circuit design and still don't have too solid a grasp of how compression circuits work, so forgive me if this sounds stupid, but have you tried replacing the switch, R9, and R10 with a 50-100k potentiometer to give more control over the decay?  Would that work or would the C9 value need to be variable as well?  I'm planning to give it a try anyway once the zener diodes I ordered get here, but was just curious of your thought on that. 

Or if my idea sounds silly, is there a better way to allow variable control of the decay?

Can I just say I fixed mine after finding a missing connection thanks to Jon for my best compressor yet.

Quote from: dan83lz on September 28, 2013, 01:41:08 PM
Quick question.  I'm relatively new to circuit design and still don't have too solid a grasp of how compression circuits work, so forgive me if this sounds stupid, but have you tried replacing the switch, R9, and R10 with a 50-100k potentiometer to give more control over the decay?  Would that work or would the C9 value need to be variable as well?  I'm planning to give it a try anyway once the zener diodes I ordered get here, but was just curious of your thought on that. 

Or if my idea sounds silly, is there a better way to allow variable control of the decay?

The decay works thusly:
Your guitar signal is rectified to a negative voltage from D3 and D4. (Read up on envelopes for further understanding, especially Mark Hammer's "technology of envelope effects" on Geofex.) This is DC, so remember it has peaks and valleys.

Negative charge is stored up in C9. This is necessary because otherwise your DC-converted signal would make the compression pulsate. The cap smooths things out. The same thing happens at the DC input of a circuit ... that's what power filtering caps are for.

To make C9's behavior more predictable, we can set a time constant by putting some resistance in parallel with the capacitor to drain off a certain amount of voltage at a certain speed. The rough calculation is uF * KOhms = mS. So 4.7uF * 22K = 103mS decay. That's pretty short. 4.7uF * 122K = 573mS. That's kinda medium. For comparison, it's a tiny bit longer than an Orange Squeezer and a second and a half shorter than a Ross Compressor.

The reason I used the switch is that the maximum threshold (comp knob) setting on the long decay is already pretty much more compression than I can imagine anyone wanting. And lowering the threshold will make the decay seem a little shorter by just not pumping as much voltage into C9. This is why I described the long switch as sort of taking over from where the short setting leaves off. A lot of settings on compressors are interactive.

This isn't to discourage you from just wiring the switch up as a 100K-500K pot. But remember too that a switch is usually cheaper than a pot + knob.

Kipper: Thanks again for building it. Glad you like it. :)

Posting for clarity on the most recent version:

Quote
The links on my page for the schematic and layout correspond to each other. My schematic doesn't really correspond to anything else at the moment, since it was a minor change but it can be built on the PCB as follows:

http://1776effects.com/wp-content/uploads/2014/02/Bear-Hug-Fab-Updated-2-15-14.pdf

Omit R13
Jumper C10
You can jumper or leave R11, it's just a limit on the comp control. (I actually forgot to leave this in on my layout and schematic, so I'll go ahead and put them in)

Follow the bill of materials otherwise.

If Josh does another run of boards, they will correspond to those changes.

So, anyone building this on my perf layout, the perf layout is exactly how I currently build them. The changes above will work for the PCB. I don't deal with vero, but it shouldn't be too hard to backtrack the current component values on IVIark's layout, since the topology is the same except for a couple omitted parts.

Jon, сompare the polarity of C6 (10mf) on the schematic and layout )))

Quote from: pba on October 23, 2014, 02:48:53 PM
Jon, сompare the polarity of C6 (10mf) on the schematic and layout )))

Yeah, it's backwards on the layout. I'm just being lazy and haven't fixed it. :( Thanks for the reminder.

Jon, do you like )))(http://www.pictureshack.ru/images/38986_21999_Bear_Hug_compressor.jpg)

Looks like it will be going in a

Bear enclosure.

8)

corrected... :)

Jon, today launched your project. Everything works fine, but there is one thing))) ... It would not hurt, rotated Q1 and Q3 to 180 degrees on the layout.  ::)
I compared with Ross/Dyna and Demeter Compulator... The sound very similar Compulator (without losing of high freq.)
Thanks Jon!

P.S. Sorry for the google translator.

Quote from: pba on October 25, 2014, 09:27:29 AM
Jon, today launched your project. Everything works fine, but there is one thing))) ... It would not hurt, rotated Q1 and Q3 to 180 degrees on the layout.  ::)
I compared with Ross/Dyna and Demeter Compulator... The sound very similar Compulator (without losing of high freq.)
Thanks Jon!

P.S. Sorry for the google translator.

:icon_redface:

Thanks for catching the mistakes in the layout -- I've updated the layout. :)

Another little thing ... Contacts 1 and 3 of pots (on the layout) must also be rotated 180 degrees ::)

Quote from: pba on October 25, 2014, 11:03:52 AM
Another little thing ... Contacts 1 and 3 of pots (on the layout) must also be rotated 180 degrees ::)

They're numbered correctly in the layout (there are numbers on the pads to be connected). I standardize my layouts to have the pots on the right side numbered 1-2-3 from the top.

Well then, no more problems. I just got used to such designations:(http://www.beavisaudio.com/techpages/Pots/images/Potentiometers-front-back.png)

Mine sounds real good! I tried the B1K comp pot but as you noted it bunches, the C1K is the way to go. Had to use a 16mm for that, which led to 16mm for the volume as well, and presented a whole set of difficulties to overcome. Well worth the effort- this build uses ¼ watt metal film resistors, Neutrik ¼" jacks, low-profile DPDT stomp switch, Millennium bypass, bicolor LED- green for on, red for compression, and SPDT on-off-on with two 220K resistors for slow, normal, and fast decay options as suggested by Jon. All in all, a difficult but very satisfying build.

Test run- success!
(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2221_zpsa5762c75.jpg)

Circuit card back side
(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2218_zps261b788b.jpg)

In-process, almost there
(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2220_zpsa425ad40.jpg)

Side view- in process
(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2212_zpsec058a59.jpg)

In-process component layout
(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2213_zpsf2b46bfd.jpg)

THAT'S.

INSANE.

 :icon_eek: :icon_eek: :icon_eek: :icon_eek: :icon_eek: :icon_eek:

@Russ: someone put your compressor through a compressor!  I feel claustrophobic looking at those gut shots.   :o

I couldn't even collect the loose parts into a space that small. I like the custom shaped board.

is it yellow for compressors?

DA- Yes, compressors get Fluorescent Yellow (maybe I should have made them red though)
Here are a couple of clearer shots:

Completed face (I need a smaller washer for the toggle)
(http://i1362.photobucket.com/albums/r688/russrutledge/Bearhug/DSCN2223_zps6c69ee51.jpg)

Gut shot and layout. The second ground from the 9V jack goes to the pots and out jack. For the sharp eyed, Q5 spot is using a 2N3904 in the build.
(http://i1362.photobucket.com/albums/r688/russrutledge/Bearhug/DSCN2225_zps5cdc894f.jpg)

Circuit card back side
(http://i1362.photobucket.com/albums/r688/russrutledge/Bearhug/DSCN2218_zps261b788b.jpg)

Component layout
(http://i1362.photobucket.com/albums/r688/russrutledge/Bearhug/DSCN2213_zpsf2b46bfd.jpg)

Side view in-process
(http://i1362.photobucket.com/albums/r688/russrutledge/Bearhug/DSCN2212_zpsec058a59.jpg)

I arranged photobucket images into folders- didn't expect them to come up as "removed"- sorry

I haven't even seen them, and they alread show as:

(http://i1362.photobucket.com/albums/r688/russrutledge/DSCN2223_zps6c69ee51.jpg)

I forgot to update this thread when the new version of the PCB was released. It has some changes to the caps for better frequency control and the bias voltage for the gate is trimable. Link in my sig -- josh redrew the schematic for me and I can't update the op.

Hey Jon!

Thanks for your ongoing support with this ol' thing.

I have an issue with my build. I am using the PCB layout found here - http://effectslayouts.blogspot.com.au/2015/07/bearhug-fet-compressor.html

My transfer was fairly successful and all traces are intact.

I am getting little compression but lots of boost. I am also getting distortion. It's almost more like a warm low gain drive pedal at the moment (with that BS170 chubby feel).

My voltages from 9.38V supply are as follows:

Q1
D 4.72 (seems to be dropping slowly, but continually every time i check it)
G0.36
S 1.97

Q2
C 7.54
B 0.56
E 0.026

Q3
D 0
S 0
G 0

I have checked for resistance between legs of the 2n5457 and getting 844ohms.

I just realised that my 2n5457 is the wrong way around... but when it's the RIGHT way around it's giving below unity when full volume (and negligible compression). When it's the wrong way around it's boosty as hell, but again with little compression.

Any thoughts? I'm bloody stumped. Cheers!

Charles

Measure the resistance across the FET when playing a chord and see if you get a resistance increase. But 844 is extremely high for a 2N5457; I rarely see anything outside 300-500 ohms. So something else might be wrong.

Your Q1 gate is also crazy low. It should be above 4V at least.

Crikey. Thanks for the tips. Will report back once I have time to sit at my workbench.

Thanks Jon!  8)

Jon, what is the purpose of the 10M resistor between the input cap and 10uf cap going directly to ground? I seem to get 4.1V or so, then when it reaches the Q1 gate, I only get 0.63V. I tried replacing it, but I have the same results.

Quote from: chuckd666 on November 06, 2015, 05:08:38 AM
Jon, what is the purpose of the 10M resistor between the input cap and 10uf cap going directly to ground? I seem to get 4.1V or so, then when it reaches the Q1 gate, I only get 0.63V. I tried replacing it, but I have the same results.

It's the gate bias resistor. The 10uF to ground is a filter cap for the bias voltage (Vb), which is formed by two 100K resistors. (The newest version uses a trimpot instead of those two 100Ks.) Something's pulling your gate down, though I'm not sure exactly what. You could try trimming the 100K between the Vb and 9V connection, or just making it smaller like it is in the Amz MOSFET Booster, and see if that brings the gate up. Otherwise check for solder bridges and all your components that connect to Q1. It's not that many.

if you try and measure the gate voltage, your meter will load the 10M resistor, and out-whack yr voltages. if youse gets good volts drain and source, you should be alright. I usually trim the bias resistors on the bb for each mosfet build.

can we see pics of your build?

I have returned with pics of my pcb.

(https://41.media.tumblr.com/4641f03e34eec2dcd26a595280b604a3/tumblr_nxfd2eT5X11qkzl6yo3_1280.jpg)

(https://41.media.tumblr.com/906a85a38017d27ba197f8fe5448cc88/tumblr_nxfd2eT5X11qkzl6yo4_1280.jpg)

Etch was ok. Messy soldering in parts because I wanted to cover up my patchy etch. Only other anomaly is the 22k and one of the 1n4148s are going into the same hole because I broke my 1mm drill bit because of my crappy drill-fu.

those "cuts" around "things" are all good/ok, are they? and pray tell, what is the pinout of your fet adaptor board (it took me a while to figure out what that was ....)?

Heh yeah there's a few correction cuts. I'm definitely still green with PCB making, but I had correct continuity when I tested it.

The FET adaptor is one of Paul Puntere's - http://www.diyguitarpedals.com.au/shop/index.php?main_page=product_info&cPath=6&products_id=375

I suppose I'll go back and quadruple check my traces. Dang it Bearhug. I will not give up on this!

Quote from: chuckd666 on November 08, 2015, 08:37:24 AM
Heh yeah there's a few correction cuts. I'm definitely still green with PCB making, but I had correct continuity when I tested it.

The FET adaptor is one of Paul Puntere's - http://www.diyguitarpedals.com.au/shop/index.php?main_page=product_info&cPath=6&products_id=375

I suppose I'll go back and quadruple check my traces. Dang it Bearhug. I will not give up on this!

Pull the FET out of the socket. What's your gate voltage now, the same? Is it still distorted? If you replace the FET with a 2.7K resistor, is it clean sounding and about unity volume?

Did you try reducing the 100K resistor between Vb and +9V?

There are only a couple places that matter for the drain voltage, and only a few components. Check them all. There may be problems elsewhere in the circuit, but get the dry path working first, then move on to the envelope detector.

I pulled the FET and am getting -0.05 on the gate. It is pretty much unity volume with or without a 2.7K resistor across it. There was probably no difference. Though it was clean!

I will try changing the 100K resistor.

EDIT: I put a 27K instead of 2.7K initially - with 2.7K it sounds very clean and slightly above unity/very slightly 'fuller' sound. Seems to be issue with the FET I suppose.

can we see a close-up of your fet board-build?

Will do, but I also have a bunch of regular Vishay 2N5457s that gave me the same results. I will double check both again and report back.

Fix the gate voltage before you bother worrying about the FET. It's irrelevant at the moment when your gate voltage is ~4V below what it should be. The FET's just a variable resistor.

Btw I worked out my problem - one of the diodes on the layout I used was oriented incorrectly.

http://effectslayouts.blogspot.com.au/2015/07/bearhug-fet-compressor.html

Please note that the topmost 1n4148 is the wrong way around! Was wondering why I was getting a large boost instead of compression from the FET (at least that's what I think it was doing). Hm.

Working really well now Jon! I have noticed there's 47pf on one schematic, and 100pf on another schematic, between the drain and the gate. I assume this is just a "taste" thing?

Hey Jon,

Another debug question... sorry in advance.

The compressor works great, but I've noticed when running it with high-treble or comparatively full-range signal chains, it's attenuating the highest frequencies. With a strat through a Deluxe Reverb or clean Marshall, for example, it seems to be cutting a lot of the jangle out.

Should I look at changing some cap values to alter how it's filtering? You mentioned early on that it should be totally transparent... I've built it stock (including the long-short switch) so have no idea what might be wrong.

Any pointers you might be able to offer would be a huge help :)

Quote from: Craggles on January 10, 2016, 01:49:35 AM
Hey Jon,

Another debug question... sorry in advance.

The compressor works great, but I've noticed when running it with high-treble or comparatively full-range signal chains, it's attenuating the highest frequencies. With a strat through a Deluxe Reverb or clean Marshall, for example, it seems to be cutting a lot of the jangle out.

Should I look at changing some cap values to alter how it's filtering? You mentioned early on that it should be totally transparent... I've built it stock (including the long-short switch) so have no idea what might be wrong.

Any pointers you might be able to offer would be a huge help :)

Which version did you build?

There are a couple things happening. I'm pretty sure it's not broken. ;)

Truth be told, the audio path does cut some high frequencies when the compression is only moderate. There's a pF cap between the drain and base of the MOSFET, which produces an increasing low pass filter (at some very high frequencies) as the gain goes up (i.e., when the compression isn't triggered). I put it there because (a) in general, when compression kicks in, the gain goes down, which can slightly reduce the treble (and also reduce distortion, which gives the impression of treble); (b) the attack is very fast, which tames high frequencies (this part can't be helped -- it's what compressors do).

I reduced the capacitor's value between versions and I now use a 22pF, but I also tend to keep it on a lower compression setting than I used to. I used to use 47pF, but Josh (at 1776) preferred 100pF so that was the value that was in the 1776 schematic for version 1.

When I say that the compressor is "tonally transparent" I'm referring to the difference between the tone when the compression is not kicking in and when it's running full tilt. When the compression is strong enough to kick the FET up to over 2.7K (and it can go higher), though, the feedback cap really is "out of the circuit" because gain = 0x (or close enough to it). I think the later versions did this better than the original version, but the principle was the same.

I suggest either playing with that capacitor or, if you're feeling adventurous, considering increasing the attack, which does involve adding a resistor (after the Q2 collector) and changing a few components.

Chuck D: I hope this answers your question, too. I'm sorry I missed your post.

Thanks for the reply Jon. Well explained as always :D

I built the vero version on lVlark's blog, with your v2.0 mods. Not sure if we're ok to link there from here, but the URI after the domain is /2013/01/bearhug-fet-compressor.html?showComment=1379340195357#c8802540165897254457

I think I might have boobed the build, as it was only my 2nd or 3rd. But then again I do remember it working perfectly back when I first built it, but then it sat off my pedalboard for a few months as the power supply was grounding out on the chassis. Maybe I fried something...

Now though, I'm noticing that the comp knob doesn't even do anything, and the pedal is *very* lightly distorting at unity volume. Something's definitely amiss - and detiorating.

I'll have another dig around, with the guts outside the enclosure, with my DMM.

For reference, I live near the ocean in Queensland, Australia, so corrosion could also be a factor.

Ahh Craggles, a fellow QLD-er.

What's the final design - the first image, drawn by Josh McClarren, or the schematic that is found in PDF link?  :icon_question:

Quote from: rankot on March 05, 2016, 03:24:02 PM
What's the final design - the first image, drawn by Josh McClarren, or the schematic that is found in PDF link?  :icon_question:

The one in the build document when you got to 1776. This forum doesn't allow me to update posts after a few days, which means old wrong links stay :(

Well, Jon, first of all, thanks for sharing this design. I built it according to your first schematic in this thread and it works just fine. Now, I tried to remove R12, R13 and C10 to make it like v2.1 schematic, and I get overdriven sound (some light clipping - could be nice to have ability to adjust it from no clipping to clipping - but how?). I have measured voltage at Q1 drain and it is 6.1V. I don't have a trimmer, just two 100k resistors as a voltage divider. Could this distortion be due to that voltage, or there is something else? Also, on the first schematic, R14 is 1M, while on v2.1 it is labeled R7 and value is 1K.

Quote from: rankot on March 06, 2016, 08:12:35 AM
Well, Jon, first of all, thanks for sharing this design. I built it according to your first schematic in this thread and it works just fine. Now, I tried to remove R12, R13 and C10 to make it like v2.1 schematic, and I get overdriven sound (some light clipping - could be nice to have ability to adjust it from no clipping to clipping - but how?). I have measured voltage at Q1 drain and it is 6.1V. I don't have a trimmer, just two 100k resistors as a voltage divider. Could this distortion be due to that voltage, or there is something else? Also, on the first schematic, R14 is 1M, while on v2.1 it is labeled R7 and value is 1K.

You have to connect the comp pot to ground, not just remove C10.

R14 blocks signal to the FET after the rectifier; in the original schematic, it cut the signal by about half, while in the new schematic that's achieved by increasing the Fv of the diodes (because the diodes used are cheaper and easier to find). 1K is better all around but you'll want to make sure you're using 1N4148 for D3&D4 because otherwise it'll compress into oblivion on everything.

Stupid me, I left compression pot hanging :) Now it works fine when I soldered it to ground, but I will try to put a switch to get distortion if needed ;). And one more thing - you mentioned in previous comments that R4 should be 4k7, while it is 2k2 in all schematics'. If I understood well, you didn't have a file to modify schematic, but this one shall be 4k7 in final design?

Quote from: rankot on March 06, 2016, 03:37:06 PM
Stupid me, I left compression pot hanging :) Now it works fine when I soldered it to ground, but I will try to put a switch to get distortion if needed ;). And one more thing - you mentioned in previous comments that R4 should be 4k7, while it is 2k2 in all schematics'. If I understood well, you didn't have a file to modify schematic, but this one shall be 4k7 in final design?

It should be 2.7K in the new version. You want it to be the same as the source resistor so that when the resistance of the FET is driven way up, you minimum gain is ~1x. Matching the source and drain resistance ensures this. The dry path is based on the AMZ MOSFET booster -- the FET is just in place of the gain control.

One question about diodes - I put some fake 1N34A, but I believe they are just some kind of shottky - voltage drop on them is 0.33V. Should I leave R7 at 1K or more?

Quote from: rankot on March 07, 2016, 08:28:03 AM
One question about diodes - I put some fake 1N34A, but I believe they are just some kind of shottky - voltage drop on them is 0.33V. Should I leave R7 at 1K or more?

I think it would be better overall to replace the two diodes (1n4148 or even 1N4001 are fine) because that puts kind of a hard "lower limit" on how big the signal has to be before it applies any compression (a little better in my experience), but if the compression's too much and you don't want to replace the diodes you can try anything between the 1K and the 1M. 1K is "might as well not be there," 1M is the original setting from the Love Squeeze's rectifier, and maybe 220-470K would probably kind of resemble the diode change, but again ... if you're replacing parts, the diodes are the better part to replace.

OK, I have replaced diodes - could't find 1N4148, but there was a couple of other Si, so I put them. I also put 1M pot instead of 1k for R7 and tried it, definitely almost no difference in compression when turning that pot, but no distortion when it is turned to 0.4-1k, so I finally left 1k resistor for R7.

After that, I tried to put 1M pot instead of R9 and SW1, and I liked it more, because I could really feel the change of decay value! So this could be an interesting and simple mod. And just to mention, I used BC550 instead of MPSA18, since I couldn't find it here. Now, I will box this little bear, and post some images when done!

PS: What will happen if I put bigger (5k) pot for compress?

I made the decay a switch to help with recall (i.e. fewer settings to remember) but I have built it at least once with a pot.

Quote from: rankot on March 08, 2016, 10:24:07 AM
PS: What will happen if I put bigger (5k) pot for compress?

5KC might be okay but finicky to dial in. Once it gets higher than 2.2K in the stock circuit, more resistance doesn't really matter: the gain for the envelope will be 1x regardless, but you might misbias the transistor, which could result in worse compression. You could make the collector resistor bigger (like 4.7K) to make it less likely to misbias, but that will mean a lower compression threshold overall, and it already has plenty of gain with the 1K turned all the way to 0. The threshold is already very low in that situation, as the gain factor for the envelope signal will be a whopping 421x at max in the stock design (including the dry path gain).

Hi there, I'm wondering if there's an etchable PCB layout for the 2.1 revision?

I looked on 1776 and Jon's website, but all that I could find was the perfboard layout and the PCB layout for the first version.

Quote from: ericlaw02 on June 30, 2016, 03:33:24 AM
Hi there, I'm wondering if there's an etchable PCB layout for the 2.1 revision?

I looked on 1776 and Jon's website, but all that I could find was the perfboard layout and the PCB layout for the first version.

selfdestroyer on Madbean might have made one. And sometimes people make them from my perfboard layouts. I'm not immediately aware of one.

Hey, I recently built the Bearhug but I am experiencing some minor issues. In general everything worked right away but I noticed some distortion when playing chords or hard picked single notes. I tried it with Q2 and Q3 pulled or with a 2k7 in Q3s position but theres always the same distortion going on. That's why I'm quite confident that it is related to Q1. When all trannies are put back it's mostly audible on low comp settings but I think thats just because the gain gets lowered initially when a strong signal enters the circuit on higher comp settings.
I also tried another BS170 I had laying around and also fiddled a little bit with the voltage on Q1s drain. Currrently it's set around 5.2V. I tried a higher resistor value (3k3) for R4.
None of the attempts described above helped :(

I made two minor changes to the circuit: I included a compression indicator LED circuit using three resistors, two caps, an LED and a 2N3904 but the distortion is also audible when this circuit is disconnected from the main circuit.
I used a 25kB poti for the Level control, just because I didn't have a 10k. But I cannot imagine this is the reason I am getting a slightly distorted signal, what do you think?

I'd really appreciate any more ideas :-) Thanks a lot for this! The circuit kinda opened the technology of compressors for me.

cheers, iefes

Edit: Forget to tell, I built the V2.1 version on perf and used the schematic on Joshs page for reference. The original perf layout is slightly modified because I used a quite large trimmer and wanted to include a tone circuit first.

I made the V1, and slowly was changing the values to the V2.
I don´t have much experience with Compressors but I find it very Subtle.
I had 3.7V in Q1´s Drain, so changed R6 to 62k (V1 Schem & Layout) and Drain´s Voltage went up to 4,7V.
I perceived a little more Compression but when play Chords or Strum hard with Humbuckers, I got some Overdrive, nice but don´t know if I wil want it always.
Another Issue is that when the effect is Turned On or Off, there´s a strong Pop noise.
Maybe, reducing the value of R1 both things will resolve.  :icon_rolleyes:

Having a problem.  No sound, or at least very little sound - as I have turned my amp up really loud and there is some coming thru.  I don't think it is responding to the compression pot. voltages (does anyone have verified, working voltages for this at hand? We have to start posting that info in these threads. If I get it working....)
BAD voltages:
BS170   S:4.5v   G:4.0v  D:5.1v
MPSA18  E: .3v    B: .8v   C: 8v
5457    all zero or less than a millivolt    signal or no signal

All stock values for V2, as found here:http://1776effects.com/wp-content/uploads/2015/03/Bear-Hug-V2-1.pdf (http://1776effects.com/wp-content/uploads/2015/03/Bear-Hug-V2-1.pdf)

I've torn this apart completely, twice, and measured all resistors, checked all parts values.  And left it alone for a day (crackerjack troubleshooting trick, or a means to suspend loud cursing fit.) Swapped all three transistors.  Almost no sound?  As in massive gain reduction?

> BS170  ...  G:4.0v

That has to be a lot lower. Like 2V. So you end up with several V from Drain to Source.

OK, that's got FET flip written all over it.
Yes.  thanks.  And I will post "good" voltages:
BS170: D:5.3v   G: 3.3v   S:4.3v
MPSA18  E: 30 to 500mv (comp pot)   B: .6v   C: 7.2v
5457    all zero or less than a millivolt    signal or no signal

These are my values:
BS170: D:5.65V G:1.9V S3.0V
BC550c: E:0.06-0.46V B:0.60-0.96V C:8.2V (variations due to Compress pot position).
2N5457: 0V everywhere

I suppose my pedal works fine.

Mine is not making me happy.  Very little compression, more like a little attenuation as you reduce the comp pot to 0 ohms.
I have the voltages 2 posts above.
The FET resistance is 300 ohm and goes up to 1500 ohms approx
The voltage at C9 goes from -.2 to -1.3v

I've tried R3 up to 4.3k, upped C9 to 10uf, swapped in schottky diodes.  At the max comp setting I get an unpleasant compression with an initial peak coming thru that sounds a bit sitarish. That same characteristic is there at the middle settings, just less of it.  I've gone to a humbucker guitar,  and get can get up to 2200 ohms across the FET and the same C9 voltages, but this is just not happening. I am getting no worthwhile compression at any setting.
As a reference, how close should this come to carbon copy?  I mean Custom Comp- which I imagine is much like the dynacomp. This was described as being less squishy than a dynacomp or ross, but I get nothing here.  Are old Dire Straights' sounds squishier than this one can offer?  But I think something is wrong, it does not sound good.

Yours is definitely not working properly. Your voltages are fine and your FET resistance at idle is normal. However, at max comp settings you should be able to easily exceed 5K of resistance and multiple volts (basically about 5, at which point the rectifier is just clipping.

If you socketted the FET, try removing it and checking that you get unity volume.

If you do, replace it with a 330R or 270R (or 300 if you happen to have it). You should get a ton of boost, and probably some clipping with humbuckers if it doesn't clip your amp.

I think a couple pages back I had a full diagnostic procedure for the sidechain, but I guess I should also say to double check the pinout of Q2. If it's backwards it will still amplify but only a tiny bit, which would explain why the compression pot still has some effect but isn't completely crushing your signal at higher settings.

Pictures might help. (I might have also missed which layout you used -- the PCB or my perfboard. I don't think I ever updated the perfboard layout to the trimpot version.)

The attack is very fast, especially at high comp settings, but the effect should be audible on pretty much every guitar by halfway on the comp knob. At the highest setting even a telecaster will usually be completely crushed. If you want I can send you some direct-to-interface recordings at various settings using whatever the closest guitar I have is so you have something to use as a sound reference.

As far as the clipping: There is almost always some clipping with the stock circuit with higher output pickups. It's a 9V circuit with anywhere from 6-10x gain at idle (depending on the FET used, but usually closer to 9x) with the stock values, so any guitar pickup that puts out a 1V or higher signal is going to clip the pedal. This would be true with pretty much any compressor except those with a much lower ratio. You either have to accept a small bass cut, accept some clipping, run the circuit on a higher voltage, or modify the drain and source resistors to lower the maximum ratio (it's the drain resistor divided by the FET resistance). However, the distortion is very soft sounding, almost like it's in the background, and I wouldn't describe it as "sitar-ish." If I'm guessing correctly that's the type of distortion I'd expect to hear on a misbiased transistor, so even though your voltages are correct, I'm not sure something isn't wrong. Your voltages are what I would expect using 2.7K on the drain and not 4.3K, for instance.

The carbon copy is a delay, so I'm not sure what that reference is.

Rankot's voltages are pretty close to my working voltages, though I think I usually end up a little higher on the gate. (I usually put the wiper of the trimpot, on that version, near 5.25V).

Correction - MXR custom comp. got it the same time as my carbon copy. Always mixing the names.

Thanks Jon, I'll go thru it again. I'm still on the breadboard, so I can freely try more FETs. I'll try the side chain.  It's good to know you are seeing some measurable misbehavior.

Well, after tinkering the Pedal, I´m back.
Changed R6 to 56k so Q1´s Gate voltage went up to 6,7V. I think it isn´t harmful to any component  :icon_rolleyes:
Also left R4 in 2k2 value.
Reduced R1 to 2M7, so the Input Impedance is not so High.
After all these changes, still got the little Overdrive when playing Chords.
John recently said that will always happen, but I´m thinking abot changing something or adding a Switch for having a Clean Comp sound.
Here´s a little Demo. First with the Line 6 POD Farm´s V Comp, and after, with the Bearhug Comp.
Regards.
https://soundcloud.com/flaconsius/prueba-compres


Been tweaking it a little and got what I wanted :-P
Just replaced Q2 for a 5089.
The result is an Ultra Clean (and very Shiny) Compressed Sound.
I am thinking of make my own Board design with both transistors and a Switch to Choose betwen "Slightly Overdriven" and "Chimey Cleany" :-)
Here´s the same Intro for Demo, and, again, first is the VST Plugin VComp, and after, the Bearhug.
https://soundcloud.com/flaconsius/prueba-compre-sor2

Jon, I've got a scope - what should I be seeing at the FET?  what is the "basically about 5..." - where should I be seeing that?

I've got everything you describe - lots of boost with a 330 resistor in place of the D and S of the FET, a faster meter shows me peak resistance there of 3k or more when the FET is back in. Voltage at C9 swings up to -2v or more,  swapping all three Qs again.  Still the envelope is very sitar-like, though I did get the volume out of it

Not sure what you'll see on a scope ... However, the FET gate is a peak-to-peak rectified DC signal that appears when you play.

When I measure with my digital multimeter using my strat at full comp, at the gate of the FET, I see as much as 5V on a hard strum and around 3V with moderate playing. (It won't go much higher than 5V because eventually the sidechain will clip, and you'll lose a bit from the decay loading the output of Q2 and the diodes.)

The other things I can think of to cut a bit of distortion are removing the zener (just be aware that at some point, it's possible to pop the MOSFET, so sockets are a good idea), and lengthening the attack to prevent "compression distortion" or whatever you want to call it when a fast attack time rides the wave peaks and makes it sound like distortion (put a resistor between Q2 and its output cap ... 2k2 would be an extra 10mS).

I have a built-up version 2 PCB in my bin. Do you want to borrow it as a reference? (It seems to have a 100K dual gang attached as the volume pot for whatever reason, but that really won't make a meaningful difference.)

It's also simply possible that the pedal simply doesn't mesh with your gear, expectations, playstyle, or whatever. Some amps might reveal shortcomings that others don't, for instance. I understand being frustrated that something SHOULD work, but sometimes, it's just "this isn't the right circuit for my guitars" ... it's why I have a shelf full of compressors, distortion boxes, etc. :)

---

I may have forgotten to put this in this thread, but soemtimes when I build these for people using higher-output pickups, I put a high-pass on the input. It's usually on a switch, and either a -3dB (1/2 R2) or -6dB (=R2) shelf filter created by putting a capacitor in parallel with the series resistor, usually around 150 or 200Hz. (It depends on the guitar.) This helps stave off some compression at the expense of some volume (but there should still be plenty available).

Quote from: Flaconsius on February 09, 2017, 07:13:37 AM
Changed R6 to 56k so Q1´s Gate voltage went up to 6,7V. I think it isn´t harmful to any component  :icon_rolleyes:
Also left R4 in 2k2 value.

How did those two changes affected the sound?

thanks for the reply Jon.  I was very interested in the Bearhug and the Engineer's Thumb, just to avoid the idea of the OTA in the audio path (silly really. Love my MXR and the many other OTA things on the pedalboard). 
I've built the Madbean 4:1 - an optical with clean blend. (I reduced R10 to 6.9K just to have ridiculous distortion available. Less than that becomes very noisy.) I like the blend more than I expected.  I think Mark Hammer pointed out somewhere the value of the blend in giving you initial attack from the clean, which of course fades quickly, leaving you the compressed signal.  This yields lots of squish but with that country-ish initial snap if you wish. Or looking at it a bit differently, you can keep the highs from the clean (initially) for when you've dialed up so much compression that your highs seem reduced. I may even filter the lows out of the clean with a toggle.
As for the bearhug and the thumb, I assume I've got something wrong - I don't doubt the design or my parts. But I'm going to move on for now.  I'll bag up the parts and label it, and let it glower at me from the Drawer of Shame.
"if at first you don't succeed, try, try again. Then quit. No use being a damn fool about it." WC Fields

Quote from: rankot on February 10, 2017, 08:08:51 AM

Quote from: Flaconsius on February 09, 2017, 07:13:37 AM
Changed R6 to 56k so Q1´s Gate voltage went up to 6,7V. I think it isn´t harmful to any component  :icon_rolleyes:
Also left R4 in 2k2 value.

How did those two changes affected the sound?

Well, I didn´t note any big difference.

I just built up a Bearhug from one of the 1776 boards. I think it's the first version of the board. It works as a boost I'm getting little to no compression? Any suggestions on how I might debug this?

here is a picture of my build. I used the mods from page 2 of this thread:

• Left out R12
• Si diodes

Here is a super gigantic image, how can you make these smaller?

(http://www.super-freq.com/wp-content/uploads/2017/03/IMG_0868.jpg)

Quote from: soggybag on March 09, 2017, 11:51:18 PM
I just built up a Bearhug from one of the 1776 boards. I think it's the first version of the board. It works as a boost I'm getting little to no compression? Any suggestions on how I might debug this?

here is a picture of my build. I used the mods from page 2 of this thread:

• Left out R12
• Si diodes

Click quote to see how I edited your post to make the image smaller. As for the build, I am at work at the moment but someone on the forum should be able to assist!
Here is a super gigantic image, how can you make these smaller?

(http://www.super-freq.com/wp-content/uploads/2017/03/IMG_0868.jpg)

There are some general troubleshooting instructions for the rectifier and FET over the course of the thread. There are similar posts on the Madbean thread if you're still stuck after browsing through this one. The tests are relatively similar for each version.

I don't see anything immediately obvious on your build from the pictures but voltages will help.

Thanks for the replies. Here are some voltages:

Q1

D - 4.93
S - 2.21
G - 2.25

Q2

E - 0
B - 8.41
C - 8.91

Q3

D - 0
S - 0
G - 0

I measured the resistance across DS of Q3 and get about 260 ohms at idle and get only a small change when there is input. Seems like Q2 or the rectifier section might be the problem. Any suggestions on how I might trouble shoot this?

Quote from: soggybag on March 11, 2017, 12:43:46 PM
I measured the resistance across DS of Q3 and get about 260 ohms at idle and get only a small change when there is input. Seems like Q2 or the rectifier section might be the problem. Any suggestions on how I might trouble shoot this?

Find out where your signal is being lost -- you can audio probe the Q2 collector for instance to make sure Q2 is amplifying. Other things to check are to make sure your diodes and resistors aren't dead or mismarked. About the only other things that can happen there are maybe the hold capacitor is shorting or something like that. It's only a small number of parts to verify, so it wouldn't even be too tedious if you have to individually test them. But start with simple ways to check the signal strength, like an audio probe.

The signal is strong at the Base of Q2 but weak and sputtery at the Collector.

Quote from: soggybag on March 11, 2017, 05:50:06 PM
The signal is strong at the Base of Q2 but weak and sputtery at the Collector.

What are your voltages?

And check the pinout.

I'm guessing the signal should be a lot stronger the Collector of Q2?

Quote from: soggybag on March 11, 2017, 06:03:04 PM
I'm guessing the signal should be a lot stronger the Collector of Q2?

Yes, it's amplified between 2 and ... 2200/47 times.

Turns out I out a 2N5087 in Q2 for some reason. Which I suppose might have worked if I had turned it around. I had an MPSA18 in the parts pin and now there is lots of compression. With Comp knob all the way up hit a chord hard the volume drops. Overall seems to be working well.

Thanks for the help!

(http://www.super-freq.com/wp-content/uploads/2017/03/IMG_0042.jpg)

Happy to help. Enjoy!

Quote from: midwayfair on March 11, 2017, 07:47:21 PM
Happy to help. Enjoy!

Hi Jon, I've got a V2.1 PCB from 1779 effects and built the Bearhug according to the given specs but I'm having some distortion issues i hope maybe you or someone else could help me with...

When i strum hard, i get a "splat" sort of distortion. Not a pleasing soft distortion. I'm using humbuckers, but i don't believe they aren't particularly high output. The distortion does reduce when i turn the volume on my guitar down. With a 2n5457, the distortion is nearly constant, completely unusable. I put a J201 in and it is significantly better, but still gets distorted on hard strums. It gets worse the higher the compression is turned up.

If i pull Q3 (J201), i get just less than unity volume and the distortion nearly entirely goes away. Only the hardest strum still causes distortion. If i remove Q2 (MPSA18) as well, there is no longer any distortion. I've swapped the MPSA18 for a 2n5089 and I get the same distortion. Below are my voltages:

BS170
D 5.2
G 2.46
S 2.99


MPSA18
E 18.4 - 364.5mv
B 0.9
C 7.36

J201 (390ohm D-S Resistance at idle, 15-20k on hard strum)
D 0
S 0
G 0

with 2n5457 (309ohm D-S at idle, 15-25 mega ohms on hard strum??)
D 0
S 0
G 0

Does anything look wrong here? Any idea why a 2n5457 would be distorted most of the time, but the J201 would be better, but still distorting?

Thanks so much.

Quote from: jbr on April 15, 2017, 10:14:54 PM
When i strum hard, i get a "splat" sort of distortion. Not a pleasing soft distortion. I'm using humbuckers, but i don't believe they aren't particularly high output. The distortion does reduce when i turn the volume on my guitar down. With a 2n5457, the distortion is nearly constant, completely unusable. I put a J201 in and it is significantly better, but still gets distorted on hard strums. It gets worse the higher the compression is turned up.

If i pull Q3 (J201), i get just less than unity volume and the distortion nearly entirely goes away. Only the hardest strum still causes distortion. If i remove Q2 (MPSA18) as well, there is no longer any distortion. I've swapped the MPSA18 for a 2n5089 and I get the same distortion.

The J201 has a higher idle resistance (you can measure them). It's about 1K, which means that the gain of Q1 in that situation is only 2.7x max (with your ratio being accordingly much lower).

There are a LOT of posts throughout the thread about distortion problems with humbuckers. There really aren't any particularly great solutions to the problem as designed, but I did have some success in cutting some bass at the input.

BUT it's kind of interesting that pulling Q2 removes the distortion -- once you've pulled Q3, the sidechain no longer affects the gain of Q1. It would also be extraordinary if you were able to clip Q1 when it's at unity gain, since that would require a signal from your guitar that's 9V, which is gigantic for pickups by themselves.

This leads me to believe that maybe Q2 is acting like a diode and clipping the signal, and the problem only really manifests with louder pickups. Try this: Lift one leg of C5, and put a 33k resistor between the lifted leg and the now-empty pad on the PCB. Put Q2 and Q3 back in.

I'll try it myself too when I get a chance.

Quote from: midwayfair on April 15, 2017, 11:29:22 PM
The J201 has a higher idle resistance (you can measure them). It's about 1K, which means that the gain of Q1 in that situation is only 2.7x max (with your ratio being accordingly much lower).

There are a LOT of posts throughout the thread about distortion problems with humbuckers. There really aren't any particularly great solutions to the problem as designed, but I did have some success in cutting some bass at the input.

BUT it's kind of interesting that pulling Q2 removes the distortion -- once you've pulled Q3, the sidechain no longer affects the gain of Q1. It would also be extraordinary if you were able to clip Q1 when it's at unity gain, since that would require a signal from your guitar that's 9V, which is gigantic for pickups by themselves.

This leads me to believe that maybe Q2 is acting like a diode and clipping the signal, and the problem only really manifests with louder pickups. Try this: Lift one leg of C5, and put a 33k resistor between the lifted leg and the now-empty pad on the PCB. Put Q2 and Q3 back in.

I'll try it myself too when I get a chance.

Thanks for the quick response.

I haven't had a chance to try your suggestion with C5 yet, but I did try placing an EQ in front of the bearhug and rolling off the bass after you said you had some success with cutting bass. Unfortunately it still seems to give the splat distortion on hard strums or picks regardless of the bass.

I'll try the resistor with C5 soon.

I forgot that the input impedance of Q2 will drop as the comp pot is turned up. I tried a 33K and it doesn't seem to hurt the sidechain. Can't comment much on whether it improves the distortion, though, since I don't seem to have a guitar that noticeably distorts it. Even my Sheraton is pretty clean sounding in the room (though I can hear some distortion on a recording when using that guitar).

Hi Jon, could I trouble you for a link to the schematic you're referring to in your most recent posts?  I have the one in the 1776 Effects build document, and based on the part numbers being mentioned I'm not sure it's the same one.  I too am having some problems with distortion that go away when I turn down the guitar a little bit.

I'm using the 2.5 schematic in Josh's build document but a couple numbers changed between versions so some older posts might not be the same.

Okay, I see a v2.1 schematic on the 1776 Effects webpage (I assume that's the Josh you're referring to), and that's the one I'm using.  To confirm, the mod you suggested a few posts ago about adding a 33k resistor in series with C5: that refers to the capacitor that goes from the output of the MOSFET booster stage into the base of the MPSA18, is that correct?

I traced most of my distortion problem to an out-of-spec 2N5457 based on one of the Bearhug threads on the Madbean forum, so replacing that made the compression a lot more reasonable and usable.  The circuit still clips when I use my P90-equipped guitar, but the same is true if I disconnect the sidechain from the source of Q1 and turn the circuit into a straight MOSFET Booster, so I think that's just something I'll have to live with.

Quote from: solderfumes on April 28, 2017, 01:17:52 PM
Okay, I see a v2.1 schematic on the 1776 Effects webpage (I assume that's the Josh you're referring to), and that's the one I'm using.  To confirm, the mod you suggested a few posts ago about adding a 33k resistor in series with C5: that refers to the capacitor that goes from the output of the MOSFET booster stage into the base of the MPSA18, is that correct?

I traced most of my distortion problem to an out-of-spec 2N5457 based on one of the Bearhug threads on the Madbean forum, so replacing that made the compression a lot more reasonable and usable.  The circuit still clips when I use my P90-equipped guitar, but the same is true if I disconnect the sidechain from the source of Q1 and turn the circuit into a straight MOSFET Booster, so I think that's just something I'll have to live with.

Yes, that's the correct capacitor.

In your case running it on 18V might actually be helpful, since you know it's a circuit headroom issue. Don't know what you boxed it in but a 1590B could fit a charge pump. Test it first, though, no sense wasting the parts if it doesn't help.

I'm thinking of building an all-bells-and-whistles version so it'll definitely be going in to a 1590B, and will try that out!

If I'm doing that, I might also try an alternative method for biasing Q3.  I saw you suggest that this would be possible either in this thread or in another forum if you had a negative power source, and if I'm throwing a charge pump in there, that could work.  I thought I had an idea of how to do it, but am realizing it's maybe not as simple as I thought.  Do you have a brief description of how this would work?

Quote from: solderfumes on April 28, 2017, 01:17:52 PM
I traced most of my distortion problem to an out-of-spec 2N5457 based on one of the Bearhug threads on the Madbean forum, so replacing that made the compression a lot more reasonable and usable.

Could you please give us more details on what specs 2N5457 has to have for this circuit, since I have built Bearhug a long ago, but I have never be so happy with the sound. I bought 2N5457 from China, maybe they are out of specs, too?

Quote from: rankot on April 29, 2017, 06:56:13 AM

Quote from: solderfumes on April 28, 2017, 01:17:52 PM
I traced most of my distortion problem to an out-of-spec 2N5457 based on one of the Bearhug threads on the Madbean forum, so replacing that made the compression a lot more reasonable and usable.

Could you please give us more details on what specs 2N5457 has to have for this circuit, since I have built Bearhug a long ago, but I have never be so happy with the sound. I bought 2N5457 from China, maybe they are out of specs, too?

Measure the resistance, it should be about 300 ohms, within about 20%. Most are.

Being out of spec doesn't change the overall sound much if at all, it just affects the compression range.

Those 2N5457 I have have 8.7k resistance between gate and source or gate or drain, but drain-source resistance is rising whenever I try to measure it with DMM - starts from some 110 ohm and then rise and rise and rise...

The 100K trimpot in the 2.1 version is for blend?

Quote from: stan-thomas on June 04, 2017, 01:52:13 PM
The 100K trimpot in the 2.1 version is for blend?

No, it's a bias for Q1. There is no blend control.

Quote from: midwayfair on June 04, 2017, 02:16:56 PM

No, it's a bias for Q1. There is no blend control.

Since this is an amazingly low part count compressor, while placing order it would be convenient for me to order the parts for the blend. If there is no phase change, can a simple blend like this be added? Moreover it would be a comfortable for a 1590B.
http://effectslayouts.blogspot.in/2015/01/simple-fet-blender.html

Would it be useful?

Anyone still have this schematic and care to share? I've looked around and only found the same dead links.

Quote from: slackshampoo on January 01, 2022, 06:26:22 PM
Anyone still have this schematic and care to share? I've looked around and only found the same dead links.

https://cdn.shopify.com/s/files/1/0022/3952/9069/files/Bear-Hug-V2-1.pdf?16138734983046189115

Awesome! Thanks a bunch