Q&D Compressor Builders......any opinion?

[markm]

Although the chip offers a great many options, it actually doesn't have to be built with anything more than a compression-amount and volume control.  Clearly, for folks like us all those other potential adjustments are too good to resist, but there is no reason why one could not simply replace some of the variable resistances (like gain, rotation, etc.) with suitably chosen fixed resistors, and have a circuit that is no bigger than a Dynacomp, no more complicated, and with a lower parts count.

This could be very interesting actually.
Thanks Mark! 

.... to follow up, I too used Marks and markm's reports to get a superb result, bufferd, gain tweaked
and external vol control add up to a superb and flexible circuit.
MM.

....and thank you Marty.....I wish I could locate that darn thread though!

[MartyMart]

That's wierd, my search from a while ago used "Q&D compressor"  including quotations and
now all i get is posts from 2000 / 2002 ??
When I type the search it "remembers" that I used "Q&D compressor" as it comes right up after
only typing "Q&  .......   search has gone bonkers me thinks !
MM

[markm]

Yeah,
I've tried several searches for my Q&D thread and come up with Zilch......

[calculating_infinity]

It's like the Trem-Lune of Compressors...... 

Now thats what I like to hear.   

Thanks for the info guys.  Yeah I have been trying to search for build reports that you speak of with no avail.  It is weird sometimes when I search for something its not there even though I KNOW its there.  For instance if I search for DS-2 mods theres only 2 or 3 topics that pop up in search, but there are more than that out there.   

Like I said I have an AMZ Jfet buffer lying around.  I will try it at the input and messing with the 10k resistor to ground suggested by Mark Hammer.  Thanks for the help guys.  I appreciate it. 

[Mark Hammer]

There are a very large number of ways to tweak this chip/circuit, and many of them are bound to be musically valid and useful for more thanyourself.  We look forward to hearing what you've done and how well it worked out for you.

In the absence of more detailed information about the RMS detector contained in the chip, it is difficult to know whether more sophisticated attack and recovery controls can be implemented for a more full-featured dynamic processor.  What we DO have access to is the averaging capacitor between pin 8 and ground.  Much like the analogous cap at pin 1 or 16 on the NE570/571, this affects both attack AND recovery time.  Making it larger in value results in a slower attack and slower decay/recovery, and making it lower in value does the reverse.  I installed a SPDT toggle in my Q&D with two cap settings, though I have been hard-pressed to hear any difference between them.  I may well have chosen values that were not different enough, though.  Given that the cap affects both parameters at once, I suspect that, like similar caps in pedals using half-wave rectifiers like the Dr. Q or Orange Squeezer, one might be able to stick a variable resistance in parallel with that cap to let it drain off faster, thereby providing variable decay/recovery time.  On the other hand, while greater compression results in greater gain reduction in most other compressors (so faster recovery resumes "normal" volume faster, hence less breathing), here more compression = more volume, so I'm a little reluctant to assume the cap works the same way here.  In any event, those with an interest in having a compressor with different personalities may be interested in trying out a variety of averaging cap values.  The appnotes suggest values between 2u2 and 22u as suitable.