Midwest Analog Sale on Whisper Compressor and other things

[Doug_H]

Doug I remember talking to you a while back and you weren't a big fan of compressors. I'm somewhat a hoarder myself. I like compressors like some guys like ODs and like Mark Hammer I'm a fan of the Anderton one too.

Clay, I don't have a lot of use for them with distorted guitar (which seems to be a good majority of what we discuss at these places :lol: ).  Seems like the pedals, amps, whatever compress enough for my tastes.

But I like compression for some clean chimey sounds. And for playing my acoustic/electric, where I may switch between 3 or 4 different playing styles in the same song (lead, strumming, fingerpick, staccato, etc) I find it almost indispensable if I want to be heard in the mix. I have a boss compressor that works pretty well for that. It can be a little noisy at times, though.

Doug

[DiyFreaque]

"Debco just blew out SN76477's for $2.00 each a few weeks ago. You never know what will come and go from those surplus suppliers."


Gasp!!

(goes from misty to fetal position).

[Mark Hammer]

[I don't have a lot of use for them with distorted guitar (which seems to be a good majority of what we discuss at these places :lol: ).  Seems like the pedals, amps, whatever compress enough for my tastes.

That's an interesting issue you raise.

It depends on whether your goal or approach is to use compressors for compression, or compressors for signal conditioning.  My sense is that a great many folks use them for compression, which is fine, but only a portion of what they can do.

For me, I like compressors because of what they do to signal consistency, rather than sustain.  So,  I may be able to get different tones by digging into my strings in a certain way, but I am obliged to have that be accompanied by a volume change.  If I use a compressor, maybe not.  Similarly, I may get a certain tone with a distortion pedal when the input signal exceeds (OR remains below) a certain level.  By maintaining a more consistent signal level, I can nail that desired tone with greater reliability.

Certainly one of the things I like compressos for is making envelope-controlled filters behave better.  In some respects, this seems antithetical.  After all if the way an autowah works is that it responds to playing dynamics, you'd think that *restricting* dynamics would take away from an autowah's character.  Well, yes and no.  Certainly it takes some dynamics to elicit a response from an envelope-controlled device.  But, with the exception of some E-H devices (and some of Steve Giles' clever designs) that use their start-and-stop-frequency circuit (which dictates how far the filter should "travel" over the designated period of time), likelihood of triggering, and extent of filter "travel", are inextricably linked via the sensitivity control in most such pedals.  Personally, I find having a moderately compressed signal, with a bit of boost, helps me to reliably extract a wah from envelope-controlled filters, without having it sweep farther than I want.

As for noise, well the magic is all in feeding a compressor the cleanest and hottest possible signal you can squeeze from your guitar.  A well-preamped guitar almost always makes a compressor perform better.  Just note, though, that since compressors generally function by starting with high gain and then reducing gain in response to larger signals, you will need to reduce the default gain in your compressor to be able to achieve degrees of subtlety in compression.

In other words, if the pedal *expects* to see a typical 80-100mv signal for single notes, and applies the sort of gain on the input stage needed by the envelope-follower to translate that input signal into gain reduction, feeding the same device a crystal clean 350mv signal will make it very hard to get anything les than max compression.  Just as important, the noise people often report being unhappy with when it comes to compressors, stems from the default gain applied at the input.  Plug your guitar into a compressor with high gain without playing anything and that noise gets boosted during the "silent" passages.  If the input signal is hot enough to drive the envelope follower, then one can afford to reduce the gain of the input stage, and the noise presented to the compressor during silent parts won't be boosted quite so much.

I can hear some of you saying "So what do I do about this?".  I guess what you can do...in SOME cases...is turn down the gain of the input stage until you reach a point where the amount of compression attainable is satisfactory at lower gain.  In the case of the Anderton design (and the Whisper),the input/gain-reduction stage is an inverting op-amp with the LDR half of a CLM6000 in parallel with a fixed resistor.  Normally the LDR is much higher resistance than the fixed resistor so gain is given largely by the fixed resistor's value.  Dropping the value of that resistor should set the default gain lower, thereby reducing the appearance of noise during silent parts.

Unless one does some other things to the envelope follower portion of the circuit, the down-side to this is that since the LDR starts from the "off" state, it adds perhaps a few milliseconds (depending ont he LDR or optoisolator poperties) for the LDR resistance to drop low enough that the combined parallel resistance drops the gain noticeably.  This will change the feel a bit in a manner that might appeal to some more than to others.

[Doug_H]

For me, I like compressors because of what they do to signal consistency, rather than sustain.  So,  I may be able to get different tones by digging into my strings in a certain way, but I am obliged to have that be accompanied by a volume change.  If I use a compressor, maybe not.  Similarly, I may get a certain tone with a distortion pedal when the input signal exceeds (OR remains below) a certain level.  By maintaining a more consistent signal level, I can nail that desired tone with greater reliability.

Yes, that's precisely the reason I use it with my acoustic guitar. Although you can turn up the "sustain" knob and get interesting compression effects, I mainly use it for balancing my sound in the mix, and allowing the more subtle techniques to be heard without drowning out everyone else when I strum chords. Or vice-versa.

BTW I like your idea of using it to limit the excursions of an env filter. I played around with some env filter circuits a few yrs ago on the breadboard, but never got around to building one. That's a good idea!

Doug

[Dean Hazelwanter]

SN76477 rules! Anybody remember the Bullet SE-01 kit? I'd give up eye teeth for that PCB now. Wish I hadn't tossed it in a manic Spring cleaning fit . . . .

Yup, just found mine (Bullet kit) again 'in a manic spring cleaning fit'.  

If only they had included an audio input that could be used with/instead of the internal VCO, it would have been the coolest chip ever made!

[Ben N]

Amen, Mark.  I used to have the compressor in front of my overdrives to get a sing-ey tone, but that got old.  Now I have it after the ODs, so I can get all my touch sensitivity and roll-down/clean-up effects, while squeezing the dynamic range enough not to get lost or overpower, and it is not all that noisy.

AFA the envelope filter idea, I would think it would always make sense to have the audio signal compressed going through so you get the full wah effect.  Perhaps a good "sensitivity" control would be to pan the envelope follower input between the compressed signal and a sidechain.

Ben

[amonte]

I've been thinking about building a compressor for a while - probably ever since I first saw the Janglebox - and I was leaning towards building an Orange Squeezer and possibly modifying it a bit.  How would these two compare sound wise?

[Joe Kramer]

SN76477 rules! Anybody remember the Bullet SE-01 kit? I'd give up eye teeth for that PCB now. Wish I hadn't tossed it in a manic Spring cleaning fit . . . .

Yup, just found mine (Bullet kit) again 'in a manic spring cleaning fit'.  

If only they had included an audio input that could be used with/instead of the internal VCO, it would have been the coolest chip ever made!

Hey Dean!

Any chance at all of you working up a clone of that PCB?  I for one would pay $$$ for it!  I thought the SE-01 implementation with the multiplexer and all was really cool.  Am I mistaken in thinking you do have an ext. input/pitch control on the SN76477, though it's not very wide range, pitchwise?  Please get in touch with me if you have even the slightest interest in the PCB idea. . . .


Also thanks, Dan N for the epeasant link.  I do have all that stuff.  I just haven't been able to commit to either breadboarding it or remaking the PCB.  And it's kind of a pain that there's no actual shematic with the Bullet kit --just another thing to have to trace out.

Joe

[CS Jones]

Mark Hammer wrote

That's an interesting issue you raise.

It depends on whether your goal or approach is to use compressors for compression, or compressors for signal conditioning. My sense is that a great many folks use them for compression, which is fine, but only a portion of what they can do.

etc...

That's another one of those amazing posts that you so often come up with - another mine full of nuggets. Brought to mind a little that thing R.G. was messing with several years ago that looked, at first blush, like a compressor but it was used to shape the signal amplitude as it approached a diode pair's conduction zones.

copy/paste/save once again.

I got the Whisper's board loaded. I rarely get to work with pre-printed circuit boards. While it's a welcome break from perfing it has the mixed blessing of causing me to rush through the build without taking more time to ponder the layout which in turn makes me pay more attention to what's happening with the circuit. I'm going to have to go back later and take more time with the circuit itself...right now I'm in the "build it and play that bad boy" mode.

Gasp!!

(goes from misty to fetal position).

That cracked me up.


Clay

[Doug_H]

I got the Whisper's board loaded. I rarely get to work with pre-printed circuit boards. While it's a welcome break from perfing it has the mixed blessing of causing me to rush through the build without taking more time to ponder the layout which in turn makes me pay more attention to what's happening with the circuit. I'm going to have to go back later and take more time with the circuit itself...right now I'm in the "build it and play that bad boy" mode.

Clay

I would love to do a paint-by-numbers build. That would be such a relief.. and fun too!

Doug

[Dean Hazelwanter]

Hey Dean!

Any chance at all of you working up a clone of that PCB? I for one would pay $$$ for it! I thought the SE-01 implementation with the multiplexer and all was really cool. Am I mistaken in thinking you do have an ext. input/pitch control on the SN76477, though it's not very wide range, pitchwise? Please get in touch with me if you have even the slightest interest in the PCB idea. . . .

Hey Joe...

Tell you what. I'll bring the board to work tomorrow, take some pictures of it and try to scan the copper layer of the PCB. If you or anyone else wants to do a PCB layout from that, go for it.  Give me your email address (either here or with a PM) and I'll send you the pictures/scans.

HTH!

[DiyFreaque]

Quote:
Gasp!!

(goes from misty to fetal position).


That cracked me up.

Try typing from that position  

I'd be interested in your impressions of the Whisper Compressor.

Cheers,
Scott

[CS Jones]

In a nutshell. I like this thing a lot.

It's not a squash 'em flat kind of effect. The initial squash stays constant throughout the compression range. The gain stage which provides the compression is set to work from unity (a resistor equal to the value of the input resistor hangs off the end of the compression pot) up to 16. This combined with the input gain stage (which was around 10 I think) which drives the rest of the circuit would lead you to believe that the thing would be pretty noisy. But it's not. It lives up to it's name. It's amazingly quiet. They've chosen low noise/low drain opamps and designed the thing around low input resistances to keep the noise down. Like the Anderton it has the LDR in parallel with the first stage's loop resistor. The second stage drives the light. As the second stage gain increases it in effect throttles down the first stage's gain due to the light's effect on the paralleled LDR. The overall effect is most easily heard when you strum hard on chords. The uneven spikeyness of the voltage variations is tamed. It works great for me with single note line playing which is peppered with chordal add ins since my right hand control has always been my weakest playing point. I overplay and it helps to tame the lack of control. At unity the compression provided gives the effect a more open feel; a less snuffing feel. I find the compression throughout the sweep of the pot usable for many different types of playing. It's versatile and effective with no "blah spots".

The roll off frequencies which result from the coupling values the designers chose to use are great. I wouldn't change a thing. These guys put together a package that suits my ear perfectly. I couldn't improve on it. The combinations for gain and frequency emphasis seem perfectly suited for guitar. Any recommendations for changes would seem to me to be merely piddling.


The real surprise here is the tone pot. Wow. Simple and elegant. Provides a huge range of usable tone adjustments. It works like a simple mixer. Treble filtered through one side of a pot and bass to the other. As the wiper travels through the range of the resistance you get a blending effect. Very, very nice. Very effective.

The level control can make the thing grow a little hairy so you've got to set that at some relatively low output point to avoid distorting. Even at low settings though there is plenty of clean boost available. Not to worry, you'll know it's on.

I like it a lot. It's made me get out and dust off my old adjustable bipolar supply unit. It's made me interested, once again, in getting around to building a board dedicated strictly to bipolars.


As far as building a compressor from scratch goes (perfing it with your own layout and not using a color-by-number approach of vero or pcb) I would much prefer building this one over the OTA based units...part for part. I prefer the opto type anyway soundwise. I've found the OTAs to be a PITA when it comes to bias balancing the differential inputs to keep the noise down as the gain level of the OTA changes. They can sound fine (if noisy) when you get them right but not much better than this one does for a whole lot less work.

Kudos to Jack Orman and Ted from Midwest Analog. And thanks again to you too Scott for bringing it up in the forum.

Clay

[amz-fx]

Thanks for your report Clay.  I'm glad you are enjoying the compressor!

regards, Jack

[moosapotamus]

I couldn't resist the deal. Ordered on Thursday, had the kit in my hands on Saturday. Awesome service (Thanks, Tom!). Nice report, Clay. I'm looking forward to building mine. And BTW... Jack, you are credited in the building instructions with collaborating on the design.

Since the Whisper shares a lot with the Anderton compressor, one of the things I was planning to do was try some of the mods for bass that Mr Hammer was kind enough to elucidate in that other thread titled "bass compressor."
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=31137

T'wer me, I would have probably gone for multiple paralleled small value plastic caps to achieve the larger value with minimal phase distortion issues, than used a larger cap.

That is a cool idea! Thanks, Mark! ... oh, and everybody else, too.  

~ Charlie

[Mark Hammer]

I've mentioned it in past, but what sometimes feels like a few months ago to me often ends up being 3 years ago.

Bill Berardi's "Fuzztain" project that appeared in Electronic Musician in the late 1980's used LED/LDR optoisolators in an extremely clever way.  The LED's in the pair of optoisolators were used in the feedback loop of a gain stage for LED-based clipping.  Ever so conveniently, those very same LEDs just so happened to shine on a pair of LDRs which were used to reduce the gain of an earlier stage in a manner almost identical to the Anderton/Whisper compressor.  So, as the pedal went into clipping, it would also compress, keeping the clipping more or less controlled (though how much clipping was need to produce gain-reduction/compression could be adjusted).  One of those ideas brilliant enough that years later I still have dead spots on my retina where the flash of light appeared.

What Berardi neglected to do, however, was incorporate one of the LDRs for a whole other effect.  You only really need one of the LDRs to reduce gain for compression so the LDR ganged to the second LED can be assigned elsewhere.  Strikes me that a perfect place might be an envelope-controlled bandpass filter (one of the filter stages in the Bi-Filter Follower) either before or after the fuzz stage.  If you ask me, a combo compressor, fuzz, autowah from so few components is about as elegant as you can get, and a terrific candidate for a one-stomp-gets-you-a-multi-FX-sound pedal.

[DiyFreaque]

Thanks, Clay - sounds mighty tempting indeed.....

While on the subject, has anybody checked out the optocouplers that Electronic Goldmine has?  

http://www.goldmine-elec-products.com/products.asp?dept=1268

P/N G15396 $0.99 apiece. They look like the Silonex type, though I couldn't say they were Silonex for sure.

Cheers,
Scott

[DiyFreaque]

I'm passing this on for Thomas Henry:

Today's the last day of the sale.  He still has some of the drum cookbooks and the MIDI stuff.

Looks like Midwest Analog may be going away here before too long  :cry:

Scott

[Peter Snow]

Hi Scott,

Whaaaaat!? I know Tom has a "real" job now but is he quitting the business completely or just a hiatus for a while?  That would be bad if he is going away for good

You mentioned a while ago that you were testing out some interesting new products for Tom - do you know what will happen to them if Midwest closes?

Thanks,

Peter

[DiyFreaque]

Well, from the tenor of the last email, it seemed like he was just going to close, but in previous emails he was going to come back in a different incarnation.  I think (as with most of these small analog businesses) you really have to like it a lot, because there's little to no money in it, and I know he's pulling some serious hours just with his teaching position.

He mentioned some chip related books he's working on, so it was a confusing mix of messages.  He's bummed that the chips he likes to write about are dropping out of production (CA3080, CA3046 at least in DIP form).  I can see where that would be discouraging.  I urged him to go ahead with those, pointing out that some BBD's, even though produced in much smaller numbers, are still accessible to this day, so the books themselves would still be useful for a long time to come.  I'm hoping he continues with the book of designs that I've seen - pretty good stuff in them.

I'll see if I can press him for more details, but I do know for certain he said that Midwest Analog itself is going to be pulled.  It's whether or not it comes back in a more streamlined form (no kits, just books, etc,) that seems to be in question.

Take care,
Scott