PYE Compressor/Limiter Thread *boards shipping* BOM up!

[Quantum J Audio]

Hi, I dont have an original analog old one and have never worked with one. So I can only compare it to a plug in. They are really close! The plug in does a little bit more static harsh thing in the highs. But this fantastic pushy thing, especially on snares, is very similar. The impact of the analog unit is more fatter, broader, does a more "musical integrative" thing. The plug is also nice but more boring.

Abe's instructions are working well on the most settings. They make sense. Things like Meter setting and starting Point of the Threshold are not perfectly written down there.
I can also recommend to take care with the transistor legs and directions (look at my pictures,...), use the correct ratios of the transformers, or it is not able to do a calibration of the compressor because it playes in the wrong ballpark - that is what I experienced at my first starting tests. Setting the correct starting point was also very important or this piece sounds a little bit nasty.
If an inductive "chopper" Oszillator can give an additional improvement,
"more original", I dont know. But for sure it is worth to try it, why not. But nevertheless I think the TI TLC555CP Oszillators are easy, cheap, and they work great in the build..
Sorry for the bad quality of the comparison

Agree with your comments about the plugin its really boring. The side chain does act differentially with a wound oscillator and I noticed a difference in sound and setup. I'm not saying it is better than the chip, but it is more true to the original design. If you scope them out they are completely different waveforms. Considering the is a PWM compressor the way the signal is modulated is going to effect how the compression sounds.

The costs was no real difference

 

[JMan]

I'd love to know more about the wound oscillator and how to put that together. Seems like it would be nice and cheap to put both options together and then just A/B to see which one suits your (one's) preferences more.

 

[Ilya]

The inductors look like Carnhill which would make sense as they are both British manufactures also supplied the likes of Neve. Potentially custom wound for PYE or off the shelf long discontinued.

Are you referring to the variable resistors as AOT's. I'm not familiar with this term?

If by inductors you mean Input/output tx, than it probably were Gardners. Looking at the photos of vintage units, I don’t see anything that looks like Carnhills.
The oscillator inductor was probably custom wound in house.
AOT=adjust on test. I referred to all those resistors marked with special symbols. They were replaced with trimmers in PI build. Originally there was just a single trimmer for decay.
As of now, nobody can explain what to look for when adjusting these marked resistors. Probably because nobody understands in depth what their function is.

 

[skal1]

any know the lead space of the 150uf caps I haven't got the boards yet

cheers

skal1

​

 

[Quantum J Audio]

If by inductors you mean Input/output tx, than it probably were Gardners. Looking at the photos of vintage units, I don’t see anything that looks like Carnhills.
The oscillator inductor was probably custom wound in house.
AOT=adjust on test. I referred to all those resistors marked with special symbols. They were replaced with trimmers in PI build. Originally there was just a single trimmer for decay.
As of now, nobody can explain what to look for when adjusting these marked resistors. Probably because nobody understands in depth what their function is.

You know a lot more about this than me on this circuit.

Regarding the AOT. I think there is so much speculation and some incorrect info on this thread about what they do it can cause confusion (it did for me) this is my view on it. Please let me know if anyone disagrees.

R23 - Not on original PYE - unity gain fully understood.
R52 - Release trim in our bom labelled as Decay on original PYE and the only trim pot on an original PYE.
VR1 -Voltage trim fully understood.
R42 - Not in original PYE added to make adjustments to meters. Meter circuit needs to be modified from bom to make the meter behave. With oscillator inductor no modification needed.
R44 - Original PYE is 220K and bom states this set and forget as HerbertR mentions recently
R48 - Bom states to use 1.8m. Same as original circuit.

As far as setup I'm only now concerned with my Decay/Release time of R52 and matching this across the two units. I can hear what this does to the sound. I believe there is no standard for measuring release time. I'm pretty sure PYE would have had a factory method.

Sonically - I'd be interested of the effects of the inductors. I also used metal film resistors unlike the original. I've also noticed the original uses some polystyrene caps.

 

[Quantum J Audio]

any know the lead space of the 150uf caps I haven't got the boards yet

cheers

skal1

​

About 3mm

 

[Ilya]

You know a lot more about this than me on this circuit.

Regarding the AOT. I think there is so much speculation and some incorrect info on this thread about what they do it can cause confusion (it did for me) this is my view on it. Please let me know if anyone disagrees.

R23 - Not on original PYE - unity gain fully understood.
R42 - Release trim in our bom labelled as Decay on original PYE and the only trim pot on an original PYE.
VR1 -Voltage trim fully understood.
R42 - Not in original PYE added to make adjustments to meters. Meter circuit needs to be modified from bom to make the meter behave. With oscillator inductor no modification needed.
R44 - Original PYE is 220K and bom states this set and forget as HerbertR mentions recently
R48 - Bom states to use 1.8m. Same as original circuit.

As far as setup I'm only now concerned with my Decay/Release time of R42 and matching this across the two units. I can hear what this does to the sound. I believe there is no standard for measuring release time. I'm pretty sure PYE would have had a factory method.

Sonically - I'd be interested of the effects of the inductors. I also used metal film resistors unlike the original. I've also noticed the original uses some polystyrene caps.

R42, R44 and R48 are of the main interest. It may be a bit hard to explain without the PI circuit at hand, but here we go.
R42 is present in the original circuit (R41 there) (5.1K going into the meter). It's clear that this is a scaling resistor, but there's no clear guidance as to how to set it up besides "adjust it until your meter movements make some sense".
R44 is 220K and corresponds to R76 in the original circuit. I haven't seen neither clear explanation regarding what is this resistor for, nor how to set it up.
R48 is 1.8M (1M in some versions) and corresponds to R77 in the original circuit). Again, nothing is known about it.

I have no interest in others because their functions are obvious.

 

[desol]

I have one of these compressors up and running. Here it is on a drum clip. Settings are ratio 5:1, 100ms decay.

 

[HerbertR]

I have one of these compressors up and running. Here it is on a drum clip. Settings are ratio 5:1, 100ms decay.

Sounds "subjective" rated like my compressor.... Very fat, smooth and clear high end, and extra juicy pushy meat especially on snares, like no other compresser does the market.... A very strong dominating character, sometimes much to much. It is very impressive to present this performance to costumers. The PlugIn does a very, very close thing. But it tends to make a stressed / wired thing, as example with the background of drums like with "non linear" room content or beating noise, resonance noise from the drums. Then the result gets often useless. This hardware clone handles this better, more musically...
Great man Cheers

 

[Rob Flinn]

Sonically - I'd be interested of the effects of the inductors. I also used metal film resistors unlike the original. I've also noticed the original uses some polystyrene caps.

The original ones I have opened up used metal oxide resistors, which are metal film. This is verified in the manual, see attached Pye list 2. The brand are electrosil which are probably a bit more common on British gear. They are my favourite resistors for p2p builds, as they have nice thick long leads.
The same list also specs most of the non electrolytics as polyester or silvered mica. See attached Pye list 1.

 

[Quantum J Audio]

R42, R44 and R48 are of the main interest. It may be a bit hard to explain without the PI circuit at hand, but here we go.
R42 is present in the original circuit (R41 there) (5.1K going into the meter). It's clear that this is a scaling resistor, but there's no clear guidance as to how to set it up besides "adjust it until your meter movements make some sense".
R44 is 220K and corresponds to R76 in the original circuit. I haven't seen neither clear explanation regarding what is this resistor for, nor how to set it up.
R48 is 1.8M (1M in some versions) and corresponds to R77 in the original circuit). Again, nothing is known about it.

I have no interest in others because

To clarify when I say not in the original PYE I mean not as a variable resistor they are fixed value. Also I made a mistake (now corrected) R52 is decay.

From looking at an internal images of the PYE and confirmed by Rob's attachment above

R42 is fixed resistance on the PYE R41
R44 Is fixed resistance on the PYE R76
R48 Is fixed resistance on the PYE R76 (1.8M vs 1M maybe just due to component availability?)

I think our goals are slightly different. I'm more concerned with an authentic sound and straight forward setup. While you are looking to fully understand the circuit.

The meter is said not to be that useful on the originals. https://resolutionmag.com/wp-content/uploads/2016/02/Cenzo-Townshend.pdf. Likely to have been a well maintained PYE at Olympic.

I can not detect any audible changes when adjusting R44. So I'll trust my ears and set and forget.

R42 - Although not in the original I will calibrate so the meter reflects gain reduction.
R52 - I will calibrate this because it has a noticeable effect on the compression

Love people posting how theirs sound. 5.1 100ms decay on drums is killer.

 

[skal1]

Hi guys,

what are you using instead of the sliver mica caps?

 

[Quantum J Audio]

Listening to R52 while changing resistance is clearly decay and sonically important to setup. However changing R42 also changes the sound of the compression.

R52 and R42 change the voltage of TR12 collector when there is no oscillator in circuit. However when an oscillator is in circuit the collector reads 0v.

Therefore I'm now questioning R42. This was fixed on the original PYE at 5.1K. While we can now control our meter with this variable resistor it should be noted this will effect the side chain thus sonically changing the compression.

I will now experiment with R42 set to 5.1K. and setup R52.

There have been various pages of the manual posted throughout this thread. Does anyone have anything relating to the setup of R52 /Decay time? I'd just like to see how the original setup of R52 compares to the 0.25vdc voltage drop that is standard on the thread.

 

[skal1]

Anyone got the schematic for this project, links are dead on the first page..

cheers

skal1

 

[Quantum J Audio]

Anyone got the schematic for this project, links are dead on the first page..

cheers

skal1

https://collectivecases.com/?product=ac-sound-pi-3141-vintage-pwm-compressor-circuit-board

 

[skal1]

cheers Electrobumps, i need the original Pye Manual ,the one that Abe was working off

cheers

​

 

[Rob Flinn]

cheers Electrobumps, i need the original Pye Manual ,the one that Abe was working off

cheers

​

Here is a Pye manual.

 

[skal1]

cheers Rob, but this attachment is text, may have sent it in wrong format

regards
skal

 

[skal1]

cool sorted it , but no schematic in manual it ok if you haven't got it
Rob.

Regards

skal1

 

[Rob Flinn]

cool sorted it , but no schematic in manual it ok if you haven't got it
Rob.

Regards

skal1

Try that.