My e-mail address is <edited by Nasse>, and dunno how big files it can handle,  :lol:

BTW, I got some unsuccesful Delivery Message from your e-mail, Peter. There happened be some overhaul at surfeu/tiscali that time so maybe it was because of it, not your e-mail address, or I did a typo

I found 572 is available for about little over 3 euros in Finland, and data sheets and application notes at Philips (just Googled NE572)

Hi Nasse,

Thanks, I'll send it when I get home this evening.

Going back to what Mark said about attack and recovery - on the NE572 both of these can be set by capacitors on pins 2, 4 and 12, 14. But when I built this compressor I used pots in addition to the caps to allow control over these two parameters.  I can't remember how I did - I'll have to dig out the circuit and refresh my memory.

Peter

If you want a really sophisticated noise gate you should think about the Drawmer DF320 noise filter. This uses a couple of That (DBX) 2150 VCA chips and a SSM (or is it an?) 2120 and some very sophisticated English circuitry.

Peter,

That's one of the advantages of the 572 over the 570/71 from what I understand.  The 570/71 obliges you to assign the two tasks to one cap.

Quote from: Peter Snow
Going back to what Mark said about attack and recovery - on the NE572 both of these can be set by capacitors on pins 2, 4 and 12, 14. But when I built this compressor I used pots in addition to the caps to allow control over these two parameters.  I can't remember how I did - I'll have to dig out the circuit and refresh my memory.

Peter:

I'd sure like to see how you did that!  For example:  would the "recovery" pot translate into a "sustain" pot, or do you have to have a dual-ganged pot controlling both the "attack" and "recovery" parameters in order to produce "sustain".

All I'm interested in is clean sustain.  I don't need to worry about any other compressor uses.  No "chicken pickin'" for me!

I have a Flatline on the breadboard now.  I must confess that this is the first circuit I've encountered that looks like it would be easier to build than breadboard!  This 572 thing looks great if I can figure out how to make it sustain -- any ideas?  Tom Scholtz didn't write the chip's app notes!

Quote from: Peter Snow
Going back to what Mark said about attack and recovery - on the NE572 both of these can be set by capacitors on pins 2, 4 and 12, 14. But when I built this compressor I used pots in addition to the caps to allow control over these two parameters.  I can't remember how I did - I'll have to dig out the circuit and refresh my memory.

Peter:

I'd sure like to see how you did that!  For example:  would the "recovery" pot translate into a "sustain" pot, or do you have to have a dual-ganged pot controlling both the "attack" and "recovery" parameters in order to produce "sustain".

All I'm interested in is clean sustain.  I don't need to worry about any other compressor uses.  No "chicken pickin'" for me!

I have a Flatline on the breadboard now.  I must confess that this is the first circuit I've encountered that looks like it would be easier to build than breadboard!  This 572 thing looks great if I can figure out how to make it sustain -- any ideas?  Tom Scholtz didn't write the chip's app notes!

Is it possible to use "steering diodes" for attack & decay on a single cap?

Hi David,

As far as I can remember I put a pot in series with each of the caps. In my ignorance I thought that would allow adjustment of the attack and decay times - and it seemed to work. But at that stage I had never built or used a compressor. Since then I have a greater appreciation of how a compressor works and what it is supposed to sound like. So I will have to dig out the circuit board and take another look - it has been a while....

Cheers,

Peter

Even if you have to use switches to select individual cap values, being able to select one cap for attack time and another for recovery time, would be a boon.

One of the things that has not been discussed much here is multi-band devices.  There is a feature article in the current (I guess soon to be recent) issue of Electronic Musician on multi-band compression.  The article devotes much of its space to software über-compressors, but the basic principles are still the same.

An old article in POLYPHONY magazine in 1982 or so outlined a two-band compressor built out of the two halves of an NE572.  The thing about compression, and to a lesser extent gating, is that the time constants needed for one part of the frequency spectrum are different than those needed for another part of the spectrum.  That particular project used a simply active frequency divider (lowpass and highpass filter) to split the spectrum up, with each segment passing through its own compressor path with its own time constant cap values, before being mixed down.  This generally makes for a more transparent compression when using gain cells like the 570/571/572, and probably when using OTA-based compressor paths as well, though I have never seen any multi-band devices using a 3080, 3094, or 13600/700.

http://www.promelec.ru/pdf/ne572.pdf

http://www-eu4.semiconductors.com/acrobat/applicationnotes/AN175.pdf

http://www.web-ee.com/primers/files/AN176.pdf


Just Googled those, maybe some info can be found there.

Mark,
We discussed this multi-band comp a while back. Could you scan the compressor article when you get a chance (No hurry, I've got a few things on the burner right now) because I'm really interested in building me one for my acoustic guitar. I think it would be really good for the extended frequencies that an acoustic puts out.

Quote from: Mark HammerEven if you have to use switches to select individual cap values, being able to select one cap for attack time and another for recovery time, would be a boon.

One of the things that has not been discussed much here is multi-band devices.  There is a feature article in the current (I guess soon to be recent) issue of Electronic Musician on multi-band compression.  The article devotes much of its space to software über-compressors, but the basic principles are still the same.

An old article in POLYPHONY magazine in 1982 or so outlined a two-band compressor built out of the two halves of an NE572.  The thing about compression, and to a lesser extent gating, is that the time constants needed for one part of the frequency spectrum are different than those needed for another part of the spectrum.  That particular project used a simply active frequency divider (lowpass and highpass filter) to split the spectrum up, with each segment passing through its own compressor path with its own time constant cap values, before being mixed down.  This generally makes for a more transparent compression when using gain cells like the 570/571/572, and probably when using OTA-based compressor paths as well, though I have never seen any multi-band devices using a 3080, 3094, or 13600/700.

I loaned all my POLYPHONY issues to Peter Snow, although I may have a photocopy sitting around somewhere.  The easy part will be finding it since we have in-laws coming to stay in a week and a half and I have to clean up.  The hard part will be getting my scanner back from my son.

Hi Mark,

Must be telepathy - I just got through reading that edition of Polyphony.  I could scan the compressor article and send it to Ed, but my scanner is down right now (changing PC's and having trouble).  Hopefully it will be back in action tomorrow night.

BTW, thanks for the loan Mark, I have nearly finished reading them all, a great set of resources and a lot of nostalgia.   I particularly like an ad in the "user equipment for sale" section at the  back of one of the early issues by some guy selling off a whole bunch of Moog analog synth equipment - the seller? Bob Moog!

Cheers,

Peter