I was prompted by some suggestions I made on another thread concerning the drive structure of the Marshall Bluesbreaker, and lured by the prospect of not having to think about how much frustration I was having with the building and wiring of some MFOS and EFM modules (more when they're done and working). The result was a thing I built last night and drew today that I'm calling the Aefea Drive (pronounced "ay-FEE-ya"). It stands for "Almost everything for everybody...almost". (With my luck it'll probably turn out to be a swear-word in Greek or Farsi!)
The basic concept is that of a single clipping/gain stage that can be used in a manner that generates more typical asymmetrical clipping, or very soft clipping, and shades in between. The Bluesbreaker, and its cousin - the Analogman King of Tone - use a resistor in series with the clipping diodes to produce a softer clip. I decided to make that clipping quality continuously variable.
The 4k7/220nf an 3k3/47nf networks exploit the Proco Rat trick of providing differing amounts of gain for the lows and low mids, and the upper mids and highs. The 3k3/47nf network provides a bit more gain for content above 1khz. At absolute maximum gain, the gain is 228x for stuff above 1026hz, and 160x for stuff below that. So, not a high-gain monster, but clips harder than a TS-9. Not nasally, but relatively bright. The 100pf feedback cap provides a treble cut beginning around 2.1khz at maximum gain.
The stuff after the 10uf output cap is borrowed from the FY-2 thing I contributed as a prize for the anniversary contest. The 1k/20k/6k8 path is where the low end passes to the output. The 20k pot is configured as a SWTC, and forms an always-in-circuit variable lowpass whose rolloff point ranges between around 76hz and 1.6khz. When combined with the 4n7 cap, it forms a midscoop network whose scoop-point can be moved around. Without the 4n7 cap, it's just a variable lowpass.
The switch shown is a 3-position SPDT that either connects the 4n7 cap, the 36k resistor, or nothing, for 3 different tonal modes. Between the three modes and variable lowpass there is a fair amount of tonal flexibility, particularly when combined with the different clip qualities.
Now, back to the op-amp. The 250k pot is wired up as a variable resistor, and is in series with one side lug of the 500k pot. The other side lug of the 500k pot goes to the clipping diodes, and has a 22k fixed resistor in parallel with it.
When ALL of that pot's resistance is between the wiper and the diodes, that side of the pot, plus the 22k resistor, puts roughly 21k in series with the diodes, and yields mild coloration. Since the max resistance beteen the inverting pin of the chip and the output is now entirely dependent on the 250k pot, max gain is limited to 76x for stuff above 1026hz, and 54x for stuff below that. So, boost but not gobs. The 21k series resistance will assure the diodes don't yield too much harshness. Note that when gain depends ONLY on the 250k pot, the treble cut begins around 6.4khz at max gain, which is bright but helps to keep some hiss out.
Rotating the 500k pot in the other direction reduces the resistance in series with the diodes (making for a harder clip), and ADDS series resistance to the 250k pot, increasing gain. The upshot is that the two controls can be used to produce restrained soft clipping or much harsher and harder clipping, at higher gains. Four knobs - hardness, gain, lowpass shift. volume - and one toggle. I've got it built into a piece of perf 9 x 18 holes, so it'll do a 1590A if you want to use those little plastic-shaft 9mm pots.
Like I say, almost everything for everybody...almost. :icon_mrgreen: I'll see if I can record some sound samples, once it's boxed up. It's nothing earth shattering, or particularly distinctive, but gets a pleasing array of tones. The output level is compromised by the passive tone network, but there is enough audible boost to keep people happy. Your basic stock Tube Screamer is not exactly an output monster either, remember, and that hasn't stopped it from being popular and useful.
(http://img.photobucket.com/albums/v474/mhammer/AefeaDrive_zpsd4393169.png)
Thanks for sharing, Mark - looks very interesting (doubtless joining "the list"). And comes with a stealable logo too!
(https://pbs.twimg.com/profile_images/1101795958/Logo_AEFEA.jpg) (https://twitter.com/aefeacre)
nice one mark, look forward to the clips man.. 8)
This is very extremelly similar to a circuit I used to design for myself in 90's (slight diffs in implementation and pot connections) and from what I gather at a first glance, this one would benefit greatly with addition of a single resistor (4k7-10k) and a generic NPN bjt as an output buffer (i.e. after the filter).
Imo it's a no-brainer.
I made layout that could be easily made into perf because most connections are pretty short. Its 15x15 holes (41mm x 41mm), smaller if you skip the traces to the row of potentiometer connections at the top and wire the controls directly to the components. Unverified for now so try to spot anything iffy you can!
Ignore the numbering in the potentiometer connection and use your head the determine the proper order of lugs.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51060&g2_serialNumber=1)
Transfer if anyone wants to etch: http://www.aronnelson.com/gallery/main.php/v/Seljer_001/transfer.png.html
Quote from: bool on May 14, 2014, 06:31:07 AM
This is very extremelly similar to a circuit I used to design for myself in 90's (slight diffs in implementation and pot connections) and from what I gather at a first glance, this one would benefit greatly with addition of a single resistor (4k7-10k) and a generic NPN bjt as an output buffer (i.e. after the filter).
Imo it's a no-brainer.
Or use a dual opamp and use the second half as a buffer
Dual opamps vs bjt buffer... imo a bjt (or a darlington, or any other discrete that would "fit", etc) adds some indescribable "goodness" to the signal that is missing when you use an opamp as a buffer.
If you are a "opamp swapper", it's less handy though. One factor more to deal with.
Quote from: Seljer on May 14, 2014, 07:30:44 AM
I made layout that could be easily made into perf because most connections are pretty short. Its 15x15 holes (41mm x 41mm), smaller if you skip the traces to the row of potentiometer connections at the top and wire the controls directly to the components. Unverified for now so try to spot anything iffy you can!
Ignore the numbering in the potentiometer connection and use your head the determine the proper order of lugs.
(http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=51060&g2_serialNumber=1)
Transfer if anyone wants to etch: http://www.aronnelson.com/gallery/main.php/v/Seljer_001/transfer.png.html
Quote from: bool on May 14, 2014, 06:31:07 AM
This is very extremelly similar to a circuit I used to design for myself in 90's (slight diffs in implementation and pot connections) and from what I gather at a first glance, this one would benefit greatly with addition of a single resistor (4k7-10k) and a generic NPN bjt as an output buffer (i.e. after the filter).
Imo it's a no-brainer.
Or use a dual opamp and use the second half as a buffer
Actually, it occurred to me that using a dual op-amp may be appropriate, given the passive signal loss in the midscoop/tone network. I suppose the buffering aspects are helpful too.
And yes, I didn't think this was anything particularly original or innovative, merely a complete functioning circuit for those who wanted to dicker around with varying degrees of hard-vs-soft clipping. I suppose another way of doing it might be to have two different diode or even diode/cap networks in the feedback loop, with a 10k pot to pan between them (the wiper of the pot goes to the inverting pin, and the outside lugs go to each of the diode networks). That would yield degrees of soft and hard clipping for each type of diode network. Basically, an extension of what you see here - http://www.muzique.com/lab/sat2.htm - but in the feedback loop.
Did some math, with the components values chosen, it's barley losing 2dB in the tone section so its not that hard of a hit. Sure lower output impedance may be nice, but 100k on the end is still less than a bare guitar.
You wouldn't really need any extra components to add a buffer by using a dual opamp, just leave the tonestack at Vref and move the 10uF cap and volume pot to after the unity gain stage. Its probably more interesting to incorporate the opamp section into the tone stack itself.
Hi Mark--
I just posted a revised "platform" for the 60 x 60 mm Bare Box perfboard in the Gallery. Would it be OK if I (or someone else) does a layout for this geared to the 6060?
OK? I'd be honoured.
Four pots and a 3-lug toggle works perfectly for the 5-pot board. :icon_biggrin:
Quote from: Mark Hammer on May 14, 2014, 10:52:24 AM
Four pots and a 3-lug toggle works perfectly for the 5-pot board.
As I noted in my other post today, I ran into an issue with combining pots and switches on the five-pots board: The bushing of the standard sub-mini toggle switch turns out to be a hair too short. I will probably have Taiway make what I need at some point. Meanwhile, Just use the five-pots board as an easy template for drilling the hole centers and use 9mm or 12mm pots.
SD
Simulated this in SPICE for a while, then built it on a breadboard. Was making a lot of different distortion sounds by dialing up that 500k log pot. I wasn't able to build the tone stack, because I didn't have a 20k pot on the shelf, so I had to use a different tone stack.
Non-the-less, this thing has some killer sound! Good work.
Thanks. And I will reiterate: there are a lot of different circuits where the interactive gain and soft-clipping/hardness pots can be applied. You can do it to any TS-type circuit, not just a Bluesbreaker.
Intresting
Thanks Mark.
I think it might be worth trying some transistors in the place of the diodes too.
High time I took Gus's drive off the breadboard and have a play with this.
??? ok that diode / feedback loop configuration is hurting my brain.
theres always 500k in parallel with the diodes, 500k to 750k with that 250k pot/variable resistor... right?
then theres also a minimum of 22k in series with the diodes a la warp style soft clipping... wait no, it can be zero series resistance in series with the 500k at one extreme , no warpish resistance in series...
would you mind walking me through what the feedback loop parallel resisance and series resistances are doing?
not that i think anything is wrong , i just cant get my head around it...
No problem, Gil.
Let's remove the 22k to make it easier. We have up to 500k that an be added in series with up to 250k for the feedback resistance. Whatever portion of the 500k pot is not placed in series with the 250 pot goes in series with the diodes. Since it doesn't take very much of that "unused" 500k to effectively shut down the action of the diodes, there is no point in having all the 500k on that side of the wiper. So, I stuck a resistor in parallel with that leg to limit how much the resistance in series with the diodes could be.
There. Make more sense now?
ahhh. ok. thank you. i see it now.wiper to one side of the 500k is a variable resistance in the feedback loop (with the 250k) , and the other side to wiper of the 500k is at the same time, inversely, in series with the diodes. and to keep the diodes series resistance side from getting needlessly high, the 22k is there as a reasonable limit of series resistance for the diode side. whew. that was crossing my eyes there for a while...
Thats my little relaxing diversion for the evening.
I built this and am dying to try it but its now 2am.
Im out of those switches but i can bodge something up in the morning for test purposes.
I cant wait to hear it. Its ages since i did a drive circuit.
Thanks Mark
I properly boxed up a 2nd build, and I am VERY pleased This thing has a LOT of sounds. Takes a bit of getting used to, to know where to set the controls, but once you get the hang of it, just tons of flexibility.
A few updates to the schematic posted earlier. The tone-mode section with the 3-way switch shows a 4700pf cap. Realistically, that maybe should be 3900pf, for a more balanced scoop, but i'll let others determine what they like. The 36k resistor should be 30k to produce the biggest difference between the middle and side switch positions.
I'm still debating about whether I need to change from a linear taper for the 500k pot, but for now linear seems fine.
The tone mode, in tandem with the shift control, just yields so many tonal options. On my Nashville Tele, I can dial in Brad Paisley-aproved middle+bridge cluck with just a hint of grit, using the variable midscoop switch position (4700pf bypass cap switched in). I won't profess that it makes it possible to sell your Crook/Dr.Z setup, but I was finding myself thinking "Hey, I've heard that sound before!" Switch to the bridge pickup, roll back a bit of treble on the guitar, dial in the soft clipping, add a bit of gain, and you have your Tom Petty rhythm sound. Turn the gain up a bit with your neck pickup and the clipping softness dialed down just a hair; set the switch to the 30k bypass resistor, and adjust the Shft control until you find the right amount of mids, and you've got your TS-9 tone. Crank the gain, turn the hift all the way up, and set the mode switch to the mid position and you have beautiful warm and round "woman tone" with just enough bass.
I just love it when I make educated guesses about where certain rolloffs ought to be, build it, and the sound corresponds to the numbers I had in mind. And this is one of those times.
I'll try and make a video demo soon. Unfortunately, I have a budget webcam whose software seems to have been uninstalled and I have no idea what the brand of the unit is to go to the corporate site and download the drivers again. :icon_rolleyes: I may try to pick up another webcam tomorrow. You won't like my playing, but you will like what this can do, and the number of different personalities it can take on. If you have a chance to try it out and provide some feedback, I'd be much obliged.
Just one question, Mark: there are two places where wires cross at right angles - one leading to the inverting input of the opamp, and one after the output of the opamp. The latter is clearly a four-way join. Is the first one all joined up too? I think "yes", but wanted to be sure.
Quote from: Mark Hammer on May 13, 2014, 07:24:52 PM
The 4k7/220nf an 3k3/47nf networks exploit the Proco Rat trick of providing differing amounts of gain for the lows and low mids, and the upper mids and highs. The 3k3/47nf network provides a bit more gain for content above 1khz. At absolute maximum gain, the gain is 228x for stuff above 1026hz, and 160x for stuff below that.
I would also assume both resistors caps are hanging off the inverting input.
Mark (Bluebunny) All those are joined.
I can confirm Simons Layout too. I built mine in perf.
Mr Hammer this has to be one of the most tonally adjustable drives I've ever built. I made the change to 30k and 39nf this morning just to test and its awesome.
I'm gonna see if i cant scrounge an on off on switch tonight at work.
Anything from a rat to a screamer to a zen and i havent even tried it with humbuckys yet.
Thanks Mr H
Quote from: Kipper4 on May 21, 2014, 04:19:24 AM
Mark (Bluebunny) All those are joined.
Thanks Rich - thought so. Eager now to build and hear this one for myself!
PS I'm using a 500kA for the shape.
Quote from: Kipper4 on May 21, 2014, 04:19:24 AM
Mark (Bluebunny) All those are joined.
I can confirm Simons Layout too. I built mine in perf.
Mr Hammer this has to be one of the most tonally adjustable drives I've ever built. I made the change to 30k and 39nf this morning just to test and its awesome.
I'm gonna see if i cant scrounge an on off on switch tonight at work.
Anything from a rat to a screamer to a zen and i havent even tried it with humbuckys yet.
Thanks Mr H
Well that put a big smile on my face, so thank YOU.
BTW, I'm assuming the "39nf" you refer to above is merely a typo and is supposed to be 3n9? or have you stumbled onto something that improves it?
Finally, thanks for confirming the layout. I also built it on perf, so it's nice to know I have something more reliable to turn to.
Looks like a nice design Mark. I simmed it and the tone section certainly looks nice and useful.
I guess the two pots in the op-amp feedback loop are fairly interactive and I wonder if replacing the 250k pot with another on-off-on toggle switch might work better (at least in terms of being able to find that sound again).
Yeah, I think there are a wide variety of other options, such as the one you describe. Heck, it could be as simple as sticking a 3-position toggle to select three different resistances in series with the diodes, and just leaving the gain pot and feedback cap in the more traditional arrangement. Essentially, an SD-1 clone with a choice of resistances for softer or harder clipping.
Me, I just liked the idea of the reciprocal control that essentially says "Oh, you want harder clipping? I'll show YOU harder clipping!" >:(. But that doesn't have to be everyone's taste. The softer clipping thing works fine without it, and the co-star tone-section can be tacked onto just about anything you want.
Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?
Yep my mistake I meant 3n9.
I played with the drive a fair bit this morning it has lots of different tone and gain possibilities.
I found it to interact nicely with with the guitar volume and tone controls too.
I.really liked how I.could set a low amount of gain, shape the tone with the 500k and low pass post and it responded well to the different playing dynamics.
I liked some of the fuzz like tones and TS type settings too.
It's small footprint and low parts count is also a bonus.
Maybe some more power supply filtering might be something I'd consider in future.
I used 1N914 diodes too.
Quote from: vigilante397 on May 21, 2014, 05:36:48 PM
Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?
It's flexible, but I doubt it would cover ALL the terrain of a Rat. Big difference in max gain. But having a Rat clone, I will say that it covers some of the same turf. Like the name says: *almost* everything for everybody....almost. :icon_wink:
But you have me curious now. I 'll pull out my Rat and try to A/B them.
Quote from: Mark Hammer on May 21, 2014, 06:27:51 PM
Quote from: vigilante397 on May 21, 2014, 05:36:48 PM
Does anyone have sound clips of this one yet? I've been considering finding something to replace my RAT but haven't found anything that can quite do the job yet?
It's flexible, but I doubt it would cover ALL the terrain of a Rat. Big difference in max gain. But having a Rat clone, I will say that it covers some of the same turf. Like the name says: *almost* everything for everybody....almost. :icon_wink:
But you have me curious now. I 'll pull out my Rat and try to A/B them.
That would be awesome. And frankly it still might do everything I need. There was a time when I was younger and I had to crank the distortion to '11' or every riff, but I'm finding with my RAT clone and my current playing style I rarely if ever turn it much past 12 o'clock. It still sounds great even maxed out ("this thing doesn't have a single unusable setting!"), but it's not what I need for the band I play in right now.
Quote from: vigilante397 on May 21, 2014, 05:36:48 PM
There was a time when I was younger and I had to crank the distortion to '11' or every riff,
yep , me too, but now i find i like tone too...in fact i dug out an old multi fx and went through a few patches ''all on 11 :icon_rolleyes:' ' dropped the distortion level
and what dya know, i could hear the notes, not a load of fluff ''around'' the notes...at around ''3-4'' was nicer and still had an edge. ...its surprising how much not maxing it matters...especially loud. :icon_twisted:
looking forward to clips/vid of this mark...or whoever builds it.. 8)
The math behind the "11" phenomenon is simple. Very simple in fact.
When you "hear" a record, it was in most cases recorded with multi-tracking (n * "doubling") guitar and other tracks, even on older records. Higher harmonics add together just as the root tones do. IOW, distortion "adds up" with the amount of multi-"doubled" tracking.
This is what you hear from the record, and this is what you want to hear when you (alone or with a bandmate or two ...) want to reproduce tonally. So, IOW, you want "11" to fill up the void.
Especially with slightly untrained ears that just want to hear "the oomph" and not really the exact tone they're playing. Which changes somewhat proportionally with the amount of time you play your instrument.. I'm not going onto details but there is a time when young guitarists discover "tonal nuances" and go reall nuts for a while trying out to find "their tone".
What in the world are you spending your time on forums like these if not for the above truism, haha?
I agree completely with the above explanation, but I had another reason for cranking to '11,' which was simply that I wasn't a very good guitarist :P Sloppy playing sounds less sloppy when you have a sloppy amount of distortion on it. I used my distortion to cover my mistakes. I don't claim to be a great guitarist now, but I've come a long way and have gone from distortion on 11 to a nice overdrive between 3-5 depending on the song. As I said, the RAT does it very well, especially when I want it a little heavier, but it's not quite what I'm looking for when I just want a tiny bit of breakup on my drive.
Quote from: deadastronaut on May 22, 2014, 06:01:20 AM
looking forward to clips/vid of this mark...or whoever builds it.. 8)
Also ;D
Okay, some crude sample clips. Two are comparing a Rat and Aefea, and two are extended trips through the tone controls at different lighter and a few harder clip settings.
Clips are my Turser Nashville Tele w/pickups I wound into the pedals into a 5F2-A Princeton and a Blue Snowflake to pick it up. Since I shot it at low res to make the upload fast, I should mention that the controls are - clockwise from lower left - Level, Shift, Clip, Gain, with the 3-position Mode toggle in the middle. Clockwise on the Shift pot moves the lowpass rolloff upwards. Clockwise on the Clip pot reduces the resistance in series with the diodes, and increases the feedback resistance to produce more gain. The Mode switch is scoop setting when flicked towards the stompswitch, variable lowpass-only in the middle position and variable lowpass+ full-spectrum-bypass in the upwards position. I futz around with the Shift and Mode controls a lot to show how tonally flexible it is. The Rodent is a GGG layout and I use an LM308. Not crazy about the taper of the gain/drive pot in it, though.
Enjoy
https://www.youtube.com/watch?v=sWiRd-N2_ik
https://www.youtube.com/watch?v=wSGYA11LRSg
https://www.youtube.com/watch?v=kJut7j00PYQ
https://www.youtube.com/watch?v=Fe_hnEMbG1A
Sounds great! Curious how this would sound driving an already over driven/high gain amp? Wonder if it will have that tube screamer effect on the bottom end with the gain almost all the way off and the level almost all the way up? .... hmmmmm might have to build and see.. I like the 20k pot notch thingy at the output!
Quote from: J0K3RX on May 22, 2014, 10:57:16 PM
I like the 20k pot notch thingy at the output!
yeah looks/sounds interesting, might have to try that 8)
3rd clip sounds almost identical to ratty at the beginning.. 8)..cheers mark.
The Rat clone does have more bottom. Hard to tell, I guess, with an 8" speaker (albeit a nice JBL 8") at a level that lets people elsewhere in the house watch TV. :icon_rolleyes:
As for overdriving a ready-to-break-up amp, well that's clearly going to have to be someone else's task. I did try to go back and forth between effect and bypass levels to give a sense of how much increase in level is attainable. It's certainly not a lot, but there are a variety of settings where it is comparable to a TS-9 in output level. Because of the level-limiting effect of the diodes, highest output levels will be achieved in soft clipping settings. And rotating the Shift control to its highest rolloff point will also allow for greater output level. As a happy coincidence, that probably yields the most useful overdriving signal.
I'm digging this one, I built it off Mark's vero layout from tagboard effects. I subbed 30k and 3n9. The output level is good, it's at unity at around 1-2 o' clock depending on the switch and Hardness settings. Realized after I built it I should have used an on-off-on switch instead of on/on. I've been looking for a pedal for my Epi Valve Jr which is on the dark side... this fits the bill. Was previously using a home-built Morning Glory, but after I sold that, and my replacement build failed, I thought I'd try something new. Definitely bright, gainier than the morning glory, and I like the increased clarity of low freq vs high freq distortion. A lot of tweak in the hardness knob.
Thanks for the feedback. I'm tickled that a tagboard layout appeared so quickly and that folks have already built it (although that's the sort of response one ought to expect when describing something as a "simple one-chip diversion", I guess).
Realistically, there are probably a few alternatives for shaping the high end. One is certainly to drop the value of the 4n7 cap down to 3n9. That will raise the corner frequency where high-end passes through unobstructed, and in so doing chop the level a bit.
On the other hand, if you like the content brought in by 4n7 but just wish it was so in-your-face, you can simply stick a fixed resistor in series with the cap. I'll suggest 3k9 to 4k7 might yield a suitable balance between bottom and top end. Alternatively, a person could stick a 5k or 10k trimpot in series with the cap, wired up as variable resistance, and just dial in how much top end they want, and leave it at that.
Mark, your demos have pretty well sold me. I'm going to have to build it. It doesn't seem to have as much face-melting distortion as the RAT, but I think that's probably fine for me.
Did we establish that the PCB transfer earlier in the thread was verified?
First one of the Hammer Palindrome series?
Hope to build it soon.
Maarten
I built mine on pref from the layout in this thread
Quote from: maartendh on May 24, 2014, 05:58:42 PM
First one of the Hammer Palindrome series?
Hope to build it soon.
Maarten
:icon_lol: :icon_lol:
Actually, because we're in the midst of a provincial election here, I was all set to call it "The Candidate". But then I thought, well, if it's trying to be everything to everybody, then why not just call it that? I was going to call it
Almost Everything For Almost Everybody, but that would have been AEFAE, whjich just sounded weird (Ay-Fay). Aefea sounded more exotic, so I went with that. Never really thought about it being a palindrome.
Quote from: Kipper4 on May 24, 2014, 06:12:55 PM
I built mine on pref from the layout in this thread
That should mean the layout is fine and it should be good to etch, yes?
Quote from: Mark Hammer on May 24, 2014, 06:20:25 PM
Never really thought about it being a palindrome.
AEFEA = chords to a song, perhaps? 8)
Hi Mark,
Thanks for this design. I plan to build it based on IVIark's vero layout at tagboardeffects.blogspot.com.
Some have reported that the sound is "bright" depending on the gain control settings (perhaps too bright), and I was wondering if (in addition to your suggestions) this could be tamed by modifying the the 4k7/220nf an 3k3/47nf networks in the gain part of the circuit. Maybe reduce the high frequency gain? Or would this change the character of the sound too much?
Quote from: Frank_NH on May 26, 2014, 08:01:14 AM
Hi Mark,
Thanks for this design. I plan to build it based on IVIark's vero layout at tagboardeffects.blogspot.com.
Some have reported that the sound is "bright" depending on the gain control settings (perhaps too bright), and I was wondering if (in addition to your suggestions) this could be tamed by modifying the the 4k7/220nf an 3k3/47nf networks in the gain part of the circuit. Maybe reduce the high frequency gain? Or would this change the character of the sound too much?
The 4k7/220nf an 3k3/47nf networks control the low end gain
If you want to tame the high end increase the 100pF in the feedback loop
Very reasonable suggestion. Note hat the feedback cap will interact with the gain and "hardness" pots such that the higher the total feedback resistance, the lower the rolloff (i.e., it gets brighter at lowest gains, and rounded off more at highest gains.)
I find the middle position on the mode switch, where the signal can only reach the output via the variable lowpass filter, yields the tamest highs. I imagine most folks will only find it useful when the gain is turned up to some appreciable amount.
Quote from: bluebunny on May 25, 2014, 10:22:21 AM
Quote from: Mark Hammer on May 24, 2014, 06:20:25 PM
Never really thought about it being a palindrome.
AEFEA = chords to a song, perhaps? 8)
I propose that all future demo clips of this pedal must include this chord progression.
I just strummed that progression now, and boy, if that doesn't have The Ventures and The Shadows written all over it.
Not made it yet but I've got my A.E.F.E.A chord sequence backing track ready.
https://dl.dropboxusercontent.com/u/54139522/aefea.mp3
Well, I have the veroboard prepped, but had to order some pots and a 3.9 nF cap :icon_confused: Getting all that from SmallBear (thanks Steve). Hope to have it done by next weekend.
I'm still thinking that modding the 4k7/220nf an 3k3/47nf networks would be interesting, but I'll build it stock for now :icon_biggrin:
All this interest triggered me into doing a perf layout at the weekend, with onboard pots. I should have all the parts, so I'll gather them together this evening and try to get it built.
Can't wait to see what you think of it Bunny.
Quote from: Frank_NH on May 27, 2014, 09:46:00 AM
Well, I have the veroboard prepped, but had to order some pots and a 3.9 nF cap :icon_confused: Getting all that from SmallBear (thanks Steve). Hope to have it done by next weekend.
I'm still thinking that modding the 4k7/220nf an 3k3/47nf networks would be interesting, but I'll build it stock for now :icon_biggrin:
The dual ground legs employ a strategy similar to the Tube Screamer in providing a gain advantage for the mids, such that they are nudged a bit closer to the clipping threshold in order to provide about as much clipping of the lows AND highs (lows will nearly always be higher amplitude, therefore clip more, if not adjusted). The TS and its kin employ only one ground leg, with a bass rolloff that starts around 720hz, and lops off 6db at 360hz and another 6db at 180hz. The dual-leg approach I used is essentially flat from around 150hz to a little over 1khz, and then adds more gain above that. So there is a midrange advantage, as in the TS, but not quite as much bass loss. A happy medium.
But there is no reason that it
needs to be that way. So, strapping a 12k or 10k in parallel with that 4k7 would get you a bass boost, and effectively de-TS-ify the circuit. That may, or may not appeal to some, but at least is simple to implement, and reverse, with a SPST toggle. It will certainly make the mid-scoop setting on the Mode switch more obviously bottom heavy, and create a greater impression of midscoop...which, I suppose would make it even more for almost
everybody. :icon_wink:
Well I finally got around to etching it as per the transfer earlier in the thread. Got it all drilled out and populated today. Everything was great and I was ready to try it out...until I realized I don't have any TL071's :icon_rolleyes: They should be here Monday, so we'll see how it goes.
I suspect any single op-amp with the same pinout will do. I just happened to use a TL071.
I'm going to have to look through the bins to see what I have. I know TL072 is a different pinout, it looks like NE5532 is different as well. I know I have some OP something-or-others lying around but I can't quite remember the number so I'll have to check the pinout after work :icon_rolleyes:
Do you know of anything off the top of your head with the same pinout?
LM741, TL061, TL081, CA3140
NE5534 has the same pinout and is half a 5532.
Very, very intersting! Definitely want to try this one out! I might try putting the adjusted amz body/tone control for a bit more tonal shaping control:
(http://www.muzique.com/images/tone2f.gif)
I opted for something that could yield a broader range of sounds. The BMP-style control, as elegant as it is, operates in reciprocal fashion. If you want more bass, it MUST be at the expense of mids and treble. If you want more bite, it is at the expense of bottom. That's absolutely perfect for some contexts/circuits, but I wanted something more chameleon-like that could get different combinations.
But ultimately, if the BMP-style control, with or without Jack's mods, works for you, go for it.
Hey Mark,
Perhaps this is a good opportunity to ask if you could elaborate further on your tone circuit in this design (e.g. how did you arrive at the resistor values outside of the first order filter e.g the 6k8). I would think that in the low pass filter mode, the roll-off at 76Hz - 1.6 kHz would be somewhat dark sounding even at 1.6 kHz (someone at the tagboard site reported this). And I guess adding the cap in parallel brings back the treble, but the bass-mids are still attenuated by the low pass filter, hence the "brightness" in this mode. I suppose I'm thinking of potential alternatives/mods for my build if it turns out to be too dark/bright for my tastes... :-\
The rather ancient midscoop filter found in so many fuzzes, but nicely illustrated in the Shin-Ei FY-2, uses 4 components. Here, we see a 10k and 15k resistor, a 100nf cap to ground from their junction, and a 1000pf cap that straddles the whole thing.
How is this a midscoop? The 10k and 100nf to ground form a singlepole lowpass filter, whole treble rolloff begins around 160hz. That's pretty low but since it is a shallow slope, there is still a fair amount of mids that pass through.
The highs sidestep everything and pass through unaffected, via the 1000pf cap. Since we couldn't have a lowpass function if that cap was tied directly to the junction of the 10k and 100nf, the 15k resistor serves to essentially isolate the highpass from the lowpass portion. Its value also serves to more or less adjust the relative amplitudes of the high and low-freq content. Voila! lows+highs and reduced mids - midscoop!
If one varies the value of the resistance leading up to the cap to ground, you change where the rolloff begins. I employed a small value resistor in series with a pot and another fixed resistor to create a fixed total resistance that runs in parallel to the bypass cap (4700pf or the suggested 3900pf, whichever you prefer). The pot allows for the rolloff point to be varied, with the pot value setting the range of adjustment, and the small value resistor setting the highest rolloff point. The 6k8 resistor serves the "decoupling/isolation" function that the 15k serves in the schematic below. I aimed for a total pot+2 resistor value that was more or less in the ballpark of the FY-2 and similar. No wanting it too scooped, I opted for a higher-value bypass cap (4700pf instead of 1000pf).
It occurred to me that if one was going to have an adjustable midscoop, produced by the pot-adjusted lowpass section, that if the rolloff could be set high enough, AND you had sufficient mids and highs to begin with, that you could simply lift one end of the bypass cap for a "rounder", less edgy sound.
As a fan of 3-position toggles, I mused about what I might be able to do with one, and realized that if I used it to replace the bypass cap with a fixed resistor that let everything through, but at a lower level (because the resistance is larger than the 1k+pot+6k8), that the variable lowpass could simply serve to introduce additional lows and mids on top of a basic full bandwidth signal.
So, the toggle gets you standard midscoop function (cap connected), variable lowpass only (no connection), or full bandwidth+variable lowpass (30k connected).
If a person finds it too buzzy overall, one possibility is to run a small-value cap to ground from the common of the toggle - say 3300pf, for starters - to roll off highest highs in any of the modes. Alternatively, one might stick a smallish value resistor after the 4700pf cap - say 2k2-4k7 - and stick a cap to ground (.015uf, if using 2k2) from the toggle lug where you are going to connect the bypass cap. I stipulate that the additional cap is connected to the switch because you don't want it to present a constant path to ground even when not selecting the additional top end. If it goes to ground from the unselected lug of the toggle, it has nothing to bleed off, and the bypass cap will still have one end "floating". Select the bypass cap for the midscoop mode and the additional 2k2 and .015uf cap will both drop the top end a little in amplitude, when mixed in with the lows, and also shave off the higher treble.
Does that make sense to you?
(http://fuzzcentral.ssguitar.com/schematics/shineify2schematic.gif)
Thanks a lot Mark! That was very helpful. I may experiment with changing the 100nF cap to 47nf or 39nF. That would boost the roll-off frequencies in the low-pass network, perhaps reducing "darkness". The 3.9nF cap and 30K resistor will remain as specified.
Okay, so I finally got my Tayda order in and got this all finished up. It sounds great (even side-by-side with my modded RAT, and I LOVE my RAT. It seems to be working like it's supposed to (aside from the couple pots I wired backwards :icon_rolleyes: ), with the exception of my gain pot, which seems to do nothing. The shape pot on the other hand seems to change the shape and the gain. Any thoughts?
I finally got my Aefea drive working this morning! :icon_biggrin:
Before I get to my impressions of the sound so far (I really haven't had a chance to play around with it extensively), a quick note on perseverance:
I made the vero board and populated it last Saturday and Sunday. Unfortunately, when I fired it up...nothing. So I checked all components, part values, placements, and orientations first. All appeared to be OK. Then I took my meter and checked for solder bridges - arghhh, found two, but STILL it didn't go. So I looked at voltages and was about to chalk it up to bad ICs last night (I have both a TL071 and several OPA134s). Then this morning at breakfast, I decided to try one more time to check continuity - what? Another solder bridge??!! Yep - between pin 1 of the IC and an adjacent track. It then fired right up! Success!! (whew). Sometimes, builds are like this, although I've gotten lucky and had a couple fire up the first try.
So...it sounds great. I stuck to the original design, with the tone section modded values (30K, 3.9 nF) and a 25K tone pot. I also used a 150 pF cap in the feedback circuit. What I noticed is that with the hardness pot maxed the gain pot doesn't have much effect. This is as is expected since the 500K of the hardness pot dominates. If you turn down the hardness, then the gain responds normally. The two controls are really interactive as many have commented previously. There's enough drive for an overdrive, but I suppose if you want more gain you can experiment by upping the gain pot values or playing around with the 3.3K/47nF, 4.7K/220nF network. It may also help to have log pots versus linear, but that's just a detail.
But what I really LOVE about Aefea is the tone control, particularly the mid scoop mode. That's a really cool sound, and something I don't have in any of my other DIY overdrives. It will be worth boxing this up for that feature alone.
My current build is a bit gnarly and has some sockets for swapping caps. I may go ahead add some other sockets so I can dial the sounds in to my liking. Then I'll remake the circuit and box it up. By the way, the OPA134 sounds great with this, but I'll check out some other ICs.
Thanks again Mark for an interesting and unique project :)
Quote from: vigilante397 on June 02, 2014, 10:13:47 PM
Okay, so I finally got my Tayda order in and got this all finished up. It sounds great (even side-by-side with my modded RAT, and I LOVE my RAT. It seems to be working like it's supposed to (aside from the couple pots I wired backwards :icon_rolleyes: ), with the exception of my gain pot, which seems to do nothing. The shape pot on the other hand seems to change the shape and the gain. Any thoughts?
The gain pot really only comes into its own when the clipping/shape pot is set to softer/softest clipping. Once the clipping/shape pot has contributed 300k or so to the total feedback resistance, the extent of clipping is enough that adding another 250k on top of that probably won't change the sound much. If ALL or most of the feedback resistance is coming from the Gain pot, then adjustments of it will be noticeable.
I used a TL071 but didn't really experiment with any other chips, to be honest. Since people have tended to have preferences for chip type when clipping diodes form part of an op-amp feedback loop (starting with the JRC4558 frenzy over Tube Screamers a decade back), I imagine it to be worthwhile to try other chips and see if they appeal more. In that respect, since the available choices increase when using duals, as opposed to singles, building it with a layout for using one half of a dual may be worthwhile. I know that when a buddy brought over his Timmy pedal (a real one, not a clone), we were pleased by the improvement made when a 1458 was installed.
This is brilliant Mark. I built it from IvIark's vero layout. The range of drive from the circuit is nuts. You really have created almost everything for everyone. Great work.
Quote
In that respect, since the available choices increase when using duals, as opposed to singles, building it with a layout for using one half of a dual may be worthwhile.
I was wondering, Mark - would this circuit benefit from a unity gain buffer at the output? Perhaps something that the second half of a dual op amp could be used for. Or I suppose you could use a jfet buffer and tack it on at the end, and still use a TL071.
Or a TL072....
I don't know that there is a need for an output buffer, but on the other hand I don't have any sense that it would suffer from one. And since it can be set to relatively clean, and has a modicum of tone-shaping, sticking a buffer/gain stage (say gain = 3-4x) after the volume pot wouldn't be a terrible thing. And if it expands the possibilities for chip choice, why the heck not?
Myself, I was aiming for something as simple and stripped down as I could get. But if complicating it a smidgen opens up more tailoring possibilities for people, have at it.
Quote from: jaredmcohen on June 03, 2014, 12:13:28 PM
You really have created almost everything for everyone.
Almost. ;D
Quote
Great work.
+1
What a great design. Thank you very much Mark.
I think this might become my favourite overdrive ever. I really like the overdrive section of the Box of Rock and I own an early 80s OD-1, of course I build myself a TS (ah – and a Blues Driver), but this one here is more flexible and just sounding better than all of them. Unfortunately I already etched a King of Tone board, so that must follow, too. But the AEFEA: Do build it! The "Everything I Need - EIN Drive" would have fitted better. Anyway, Mark designed it and he named it, so I stuck to it.
Here are some pictures of my first (maybe not the last) build. I put a dual op-amp in there, because the drawer looked fuller than the one of the single op-amps. The fullest box contained 4558s (when I began building pedals I still thought that is the only op-amp for overdrives so I ordered too many of them), so this was it. Maybe others sound better, but for me there's no need at the moment. I think I'll have to fiddle about with the switchable 4n7 – the sound is too brittle for my taste.
(http://i1244.photobucket.com/albums/gg578/lars-musik/Musikkram/AFEEAs.jpg)
For all the 1590a fans, here's a layout.
(http://i1244.photobucket.com/albums/gg578/lars-musik/Musikkram/AEFEA_1590a.jpg)
Best, Lars
Well, a year and a half after I said I'd build this, I finally finished it!
(http://www.bouron.org.uk/marc/aefea1.JPG)
Did a perf layout with board-mounted pots. I have a short, because the volume pot doesn't do anything! So I'll have to take the board out and fix that, but otherwise it was worth the wait. Thanks, Mark.
Hey, thank YOU.
I'm always honoured when someone thinks that it's worth their while to invest their time and money in something that came to me on a whim. I hope you enjoy it for a long time.
And yes, the 4n7 cap/path is a little shrill. It may be a good idea to stick a resistor in series with it just to tone down its contribution to the mix. Maybe try 6k8 to 12k.
I'm just planning a two-in-one pedal with the AEFEA and a distortion pedal, maybe somethings with a Marshall-like sound.
Did anybody try how the AEFEA stacks with other drive pedals? I might use the Catalinbread Dirty Little Secret (Mk1), but that's quite bright as well. And I use a AC30 Top Boost, which really needs drive pedals with the ability to tame the treble...
I'll use a varibale relay switching, that allows for both popular wirings of two footswitches (a) each circuit has its individual bypass switch, b) one switch toggles from circuit 1 to circuit 2, the other bypasses the whole pedal.)
I think it should probably work out nice if one uses the "middle" toggle setting (variable lowpass with no treble bypass) and sets the unit for soft clipping.
I finally got around to finish my AEFEA. What a great pedal! Thanks Mark.
It's been quite a long process. I started AEFEAing my Tube Screamer by replacing the original feedback loop with the aefea's on a daughter board. A recommended mod for a tube screamer. Unfortunately I pretty much ruined the vero board with broken and lifted pads when experimenting with the tone stack. So I decided to ditch the ts and build an aefea from scratch. But it was a fun process.
I just have one question: I have never built or played a Rat but I like the rattier sounds of the aefea. I saw the Rat has a pair of diodes to ground and I tried to add them to the aefea, but it really didn't make much of a difference. Slightly lower volume and slightly different sound. Is that expected behavior? I had expected something more dramatic ie. more drive. I tagged the diodes to pin 1 of the tone pot.
Thanks for the positive feedback. I appreciate it.
The problem with your attempt to Rat-ify the pedal is that you still have the feedback diodes in place. So when you increase the gain to get clipping out of the additional diodes, the unit is already clipping. Because there is an asymmetrical trio of diodes in the feedback loop, and you're adding a back-to-back pair on top of that, there likely won't be much of a noticeable increase in clipping, but there will be a drop in volume because a 2+1 diode complement results in a roughly 1/3 higher output than a 1+1 pair. The second pair of diodes reduces that 1/3.
That said, if you adjust the 500k clipping-hardness pot so that you end up with the 22k in series with the diodes, you will reduce the degree of clipping in the op-amp, via the feedback path, and provide a hotter output to your additional diodes. Under those conditions, your added pair will be responsible for more of whatever clipping you hear.
Alternatively, just use a toggle to disconnect the feedback diodes from the output of the op-amp.
I understand why you were prompted to consider a Rat-like arrangement. Much like the Rat, this circuit uses two "tails" to provide differential gain for the bass/mids and highs. Of course, where the Rat has gain in the thousands, this one doesn't apply more than 230x gain for the highs; more than a TS-9, but clearly not even on the same continent as the Rat.
Thanks, Mark. I was thinking along those Lines, that the extra diodes did not contribute much. But I must admit that I missed that the rat did not have any diodes in the feedback loop when looking at the schematic :icon_redface: so your suggestions makes a lot of sense.
I think I will try a switch that switches out the feedback diodes and switches in the diodes to Ground.
I could also just build a rat :icon_mrgreen:
Given that some of the magic of a Rat comes from the use of an externally compensated LM308, and much less comes from the use of diodes to ground, making a Rat might not be such a bad idea. On the other hand you could use the diode switch to contrast between asymmetrical clipping (stock) and symmetrical hard clipping. Might sound different. Might be appealing to you. You never know until you try.
Leds in opamp nfb running into silicon diodes-to-ground clipper is a time-tested combination.
Quote from: bool on March 17, 2019, 07:22:56 AM
Leds in opamp nfb running into silicon diodes-to-ground clipper is a time-tested combination.
So that by the time the hard clipping, high threshold LEDs kick in, you're already well up into the gain range of the pedal, and then you get that little extra bit of limiting?
That "little bit extra" depends on how much "gain" you dial-in. Mainly, it's a different method of hard-clipping, and it gives a bit more consistency compared to running a opamp into rails (which depends on exact rail voltage - meaning the circuit will work different if your battery is low or if it is brand new ...).