Pye Compressor

Does anybody know what opering concept does this Pye compressor uses?


http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=150190892590&ssPageName=STRK:MEWA:IT&ih=005

It appears to be a feedback compressor/limiter like an FET based unit only using a bi-polar transistor as the gain control element. That probably accounts for the low compression ratio range, the highest compression factor being 4:1. This is going to be an extremely marginal circuit. For the >10K price, the buyer could have gotten almost 8 channels of brand new UA 1176s. ????

$10,999 USD - that's an early April fool, right? Sheesh... It's a nice compressor, but at that price? That's insane...

You can see a schematic for one of the versions here: http://recforums.prosoundweb.com/index.php/m/179486/0/

There are at least 4 revisions of Pye comps. As the schematic shows, it's a 'mark space', diode-bridge affair. They are lovely, but a pair for $11,000 USD? :shock:


Justin

I think it's actually a PWM type.

Ian
EDIT: Oh... maybe I'm mistaken. Gonna take a closer look.

Some more links here (pdf is way cool): http://www.coralsound.com/pyebook.pdf

http://www.groupdiy.com/index.php?topic=3841&highlight=pye

When I first took the photo in my earlier post (with a camera - sorry about that!), it was put up at the original Tech Talk forum, where PRR and others got their teeth into its design in a big way.

Unfortunately, due to a sociopathic jerk who hosted the group, we no longer have access to that discussion...


Justin

At first, I thought it was a bridge-type gain control (a ring modulator), but if you examine the schematic, you will see that the bridge is actually the rectifier that derives the control feedback. Transistor TR11, I believe, is the device that is doing the gain control and according to the manual is PWM.

They are definitely PWM or 'chopper' type units.
When I worked at Morgan Studios in the 70's they were the main compressors for use on guitars etc.
'Allright Now' by Free - almost eveything on that track went through Pye units.
If I remember rightly they had a really low rail voltage - something like 16volts (may even have been -16v !).
I must have a look at the schematic after all these years.

Martyn

Ah. That pdf file is the manual without a schematic. The other links appear to be dead. Anyone have the circuit ?
I tell you another record that has some outrageous Pye Compression on it:
'Hole in My Shoe' by Traffic.
The drums are squashed to oblivion on that (Olympic Studios I believe).
Update. I've just checked and the circuit on Prosoundweb is still there.
Must download it and have a scan through.
Oh and the units we had were proper 1/2 rack 2u modules - not the type on that eBay sale.

I seem to recall being able to buy one of these for pennies not that long ago (well, something like £100) but I didn't bother. That happens to me often.