Cascading Compressors / Attack

[AlexK]

I'm building a compressor similar to an Analogman Bi-Comp (Dyna/Ross + Orange Squeezer) and I was wondering how useful it is to be able to cascade the compressors. Does anyone do this? My original thought would be just to have one stomp to turn the effect on, and a mini-toggle to switch between the Dyna and the OS.

Also, how useful is the attack pot on a Dynacomp? I can make it external if I go to a larger box.

Any Thoughts?

-Alex

[Paul Perry (Frostwave)]

It might be more useful to PARALLEL the compressors, with a tone control at the front of each, so you can have a different time constant for high & low frequencies.

[AlexK]

That's a great idea.  Thanks Paul.  Hmmm...what else could I do with 2 compressors?

-Alex

[Mark Hammer]

I added an attack control (it is a decay control, actually) to a Ross clone made with the Tonepad layout on a box made for a buddy recently.  It consisted of a 10k resistor and 250k pot with a parallel resistor to put me in the 150k (max) zone.

The control provides a subtle but audible effect.  With max "attack" resistance (the default) the sound is extremely squishy with high compression.  It also tends to lose a bit of brightness as well.  With reduced attack, you tend to retain the feel of the bite of each note even though the level is obviously held constant.

Even though it is a worthwhile addition, the effect is subtle enough that I'm not sure it merits the expense of a pot and knob.  If you stuck in a 180k fixed resistor instead of the 150k one, and used a 3-position (on-off-on) SPDT toggle to tack on each of two different parallel resistors to get effective resistances of 10k and maybe 50k or so, I think you'd get pretty much the same utility as a pot.  I find myself needing to rotate the control all the way to one side or the other to hear differences, so having a switch that mimics that (plus a "middle" position) is probably enough.

Are two cascaded compressors of any use?  Depends.  The response of the 2nd envelope follower could conceivably be smoother if each unit was set to moderate compression.  On the other hand, hard compression of the first would produce little audible effect out of the 2nd, other than the boosting effect it provides.  A boosting effect, however, could also produce the same effect if placed ahead of the compressor.

You will note that the compression amount control is simply a variable resistance, which makes it a prime candidate for stompswitchability, using a SPST switch and a parallel pot.  This would give you the option of going from a higher to lower amount of compression (or vice versa) with a second switch.  The only caveat is that compression amount and output volume are yoked in the Dynacomp/Ross.  Still, this is not unlike having a speed-1/speed-2 switch on a phaser or chorus....handy sometimes.

[AlexK]

Mark, every question I've asked here you always reply with the most thought out and comprehensive post possible, thanks a lot!!

I'm using a tonepad layout too.  I thought the decay would be controlled by the 2k trim pot (guess I was way off on that one).  So what resistor is replaced by your combination pot/resistor?  I already drilled the enclosure for an extra pot, so I might as well put it in.

I don't think I'm going to go the series compressor route.  The only reason I even considered it is b/c of Analogman's, but it didn't seem very useful.

Is there an article online about modding compressors similar to "the technology of..." series?

Thanks again,
Alex

[Mark Hammer]

Thanks for the compliment.  Gracious of you.

The resistor in question couldn't be situated in a more convenient location.  It's the 150k resistor right beside the +9v pad between the two existing sets of pads for the pots.  I think the easiest way to do it is simply to stick in a 180k resistor with the resistor itself sitting a little off the board.  Before you install that resistor on the board solder a wire lead to each side of the resistor and THEN insert the resistor leads into the holes. Those wire leads can now run to a switch for changing the decay/recovery time in the manner you prefer.  If you parallel a 12k resistor with the 180k you get 11.2k, and if you parallel a 68k resistor you get just over 49k, so those are probably some good values to experiment with if you choose to use a 3-way switch.

There is a good review article on compressors from 2001 at the Electronic Musician website, but there probably could be room for an in-depth "technology of..." paper on sidechains in general, indicating how they serve things like compressors, noise gates, duckers, etc., along with some of the standard simple sidechain design templates.  You'd be surprised how many effects use the same sidechain as the Dynacomp, right down to the same component values.  It was the similarities between the Dynacomp, Boss CE-2 and the Pearl and Nobels units that led me to try to the "attack" mod.

[george]

Hi Mark

don't you mean "Boss CS-2"? otherwise I'll be tearing apart my CE-2 tonight wondering why it won;t compress :-)

george

[Mark Hammer]

:oops:

Between the frequency with which I type CE-2, and the fact that E and S are right near each other, bound to happen I guess.