Better ICs for a Ross Compressor?

[phillip]

I was going to order all the various parts for a Ross Compressor and I was wondering if there were possibly any better ICs for the pedal that would work even batter in place of the original CA3080.  Obviously, it would need to have the same pinout.

Does anyone know of a possibly better one?

Phillip

[Paul Perry (Frostwave)]

The 3080 is it. They are all the same, IMHO. It might be possible to redesign it around half a LM13700 or equiv, usign one of the voltage controlled amplifier ckts from the diy-synth guys, but.... it would be twice as big then, and probably not noticeably better.

[Mark Hammer]

A number of other comparable compressors from Boss and Pearl or Nobels use higher quality OTAs in what is essentially the same design.  Typically, these are made by Rohm: the BA662 and the BA6110.  The 662 is apparently a proprietary chip made for Boss only.  The 6110 is available to mere mortals, but hard to get.  Both have better distortion specs than the 3080.  Jim Patchell (do a search for Patchell and "old crow") is quite fond of the CA3280, which is a dual OTA with much better distortion specs than the 3080.  None of the chips listed could easily sub for the 3080 without nopticeable modifications to the design, and certainly none would permit you to pop one chip out of the socket and stick another in the way you could with op-amps or even the transistors used.

Having said all of that, there may well be some merit to exploring the transistor that precedes and immediately follows the 3080 in the circuit.  Although 3904's, etc will "work", there are certainly many more alternatives out there that may yield lower noise performance in those positions, many of them actually designated "low noise" (which 3904 and other comparable ones aren't).  The three transistors involved in gain control of the 3080 itself probably won't benefit the tone much, if at all.

[phillip]

Hmm do you think that BC109Cs would work better in the circuit than 3904s?  I have a bag full (30 or 40) of those that I got about a year ago and haven't found a home for them yet.  The 109C is a low noise transistor that's known to sound pretty good in audio circuits.

I also have quite a few 2N5088, 2N5089 and BC549C.

Phillip

[Mark Hammer]

Socket the pedal, memorize the pinouts, and let your ears decide.  The 5089 is lower noise than the 5088.

Please note that if anything about the transistor *increases* signal level, you will want that transistor *after* the 3080, not before it.  The CA3080 starts to clip around 100mv input.