Building a NE572 compressor..

[dschwartz]

I have a NE572 and a 571 in my IC stock, i bought them hoping to make a simple, ordinary, basic compressor out of them, but i just cant find a single circuit based on those IC´s..

YES..i searched the forum, but i couldn´t get anything usable...just some thoughts and ideas..

the datasheets for this chips are very vague, or i didnt really understood how to make a usable compressor with it...


does anyone have a schematic, pcb or anything based on this chips? i´m thinking a copressor, but any circuit will do...i just want to feel that buying those chips was a good idea....

thanks!!!

[Jaicen_solo]

Check out the Rocktage on Generalguitargadgets.com, that uses an NE570 as a Compander.

[StephenGiles]

Home & Studio Recording had a 572 compressor article - I remember that edition had a pale blue cover and in August '83 Polyphony: The Penultimate Compressor. I have seen another compressor circuit using that chip, maybe Rane or Symetrix.

[Arn C.]

I could not find the "rocktage" on GGG.  Where is it?

Thanks!
Arn C.

[StephenGiles]

http://www.freepatentsonline.com/4754230.pdf?s_id=11da114ec04ad7718436b7b817f212a7

[George Giblet]

One of the magazines used an adaptation of the philips application note:

  http://www.nxp.com/acrobat_download/applicationnotes/AN174.pdf

See figure 12, page 5 - note this is a had limiter.   IMHO it's not that great.

The app note has a fixed threshold but the magazine article made the threshold adjustable.

I don't remember seeing the magazine version Stephen Giles mentioned.

[Mark Hammer]

I have the POLYPHONY NE572 project article in question, and may even have a scan of it.  It's a pretty deluxe unit by many standards, using frequency splitting and dual-band compression, which should produce a more transparent sound.  Unfortunately, while there is a schematic, there is no layout.

[dschwartz]

well that woulk be great! ... i can redraw the schematic on expressPCB and make a board and layout...is the information what´s important...

PD: on the few circuits i found, i noticed that non of them had control for attack or decay or threshold or any....the circuit for a compressor is there, its just that i want to know how to control those parameters....

[Mark Hammer]

The NE570/571 uses a single cap on pins 1 and 16 to provide the time constants.  Unfortunately, unless one shifts to a substantially more complex support circuitry, this does not permit an easy differentiation between attack and recovery, merely a global "How do ya want it?  Faster or slower?".  The NE572 improved upon this by permitting separate attack and recovery cap selection on pins 4/12 (attack) and 2/14 (recovery).  I suppose it is possible to either implement step-wise variable attack and recovery using a switched set of cap values, or to implement  a continuously variable recovery using a variable discharge resistance in parallel with the recovery cap.

[dschwartz]

thats very good information!!!! thanks!!!!!

[StephenGiles]

The NE570/571 uses a single cap on pins 1 and 16 to provide the time constants.  Unfortunately, unless one shifts to a substantially more complex support circuitry, this does not permit an easy differentiation between attack and recovery, merely a global "How do ya want it?  Faster or slower?".  The NE572 improved upon this by permitting separate attack and recovery cap selection on pins 4/12 (attack) and 2/14 (recovery).  I suppose it is possible to either implement step-wise variable attack and recovery using a switched set of cap values, or to implement  a continuously variable recovery using a variable discharge resistance in parallel with the recovery cap.

The H & SR design tried to get over this problem, I'll try to find it.

[Mark Hammer]

If I remember correctly, separate A and R times were attainable with an NE570, except that it would take an extra 4 op-amps or something like that to do it.  At that point, the 570 stops being a one-chip solution and turns into something on par with a completely discrete solution.

[dschwartz]

well i have a ne572, so. i can use that cap/pot parallel solution.. sounds good to me.. thanks!

[StephenGiles]

http://www.google.com/patents?vid=USPAT5159636&id=XiAhAAAAEBAJ&printsec=drawing&zoom=4&dq=Audio+signal+expander+apparatus

Nice patent with parts values!

[StephenGiles]

http://www.repeater-builder.com/ge/lbi-library/lbi-38119d.pdf
another one!