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

[Spencerleehorton]

I’ve got the pye on the bench again to try and figure it out!
I’ve set my unit using some voltages that have very kindle been supplied.
I can post voltages to transistor if anyone wants them but I’m still not confident I’ve got the unit functioning yet!
First some questions:

Where should the Vu meters be set, in the middle or to the left? I’ve seen them all to the left but the original is sort of in the middle?

When slowing down the release should the needle move to the left?

The sidechain txf says 1:1 in Pcb but I’ve seen it say 1:4?

Input txf 1:1 or 2:1?

Output txf 1:2 or 1:4? Or use a preamp to boost?

True bypass info?

 

[Spencerleehorton]

right, well i've been tweaking and if i ignore the meter being at just left of half way on both meters, i've got a very respectable working unit.
Tiny bit of top end hiss but you would expect that from any unit.
i don't quite know what i've done yet but i've gone with the following:

input txf = 1:1
output txf = 1:4
SC txf = 1:4

i've used BC560C, BC550C, 2N3609 in replacement of BC550A and used 2N5088 and PA3640.

B- voltage is -16.55v

i've put the 1M8 resistor in, the 5k trim pot i've put in the middle somewhere, the R23 i think is about 220k, most of the tweaking was done on what i'm calling the input/output pot as it seems to me to be the most critical.

Im going to continue tweaking as i would like to get more compression out of it, as with input volume at max and output at half way the needle is only moving a a little and it could move double the distance.

will update once i find out more.

 

[Spencerleehorton]

reading through the thread again ive learnt a few more things:

going to set R48 correctly so to set zero on the meter

going to sort out the wiring and tidy everything up and bolt it all down

gonna change the L1 choke for lower ohm version, self wind

R23 = compression amount, probably threshold?
R44 = set to 220k
R42 = set to 5.1k
R52 = meter zero (max to one side to get near zero)
R48 = 1M8, lower if cant get to zero

going to change Vu Meter LEDs for something more powerful

my meters are hairball 1mA and im using input pot and output pots, i have stepped pots as well but will try on separate pots first.

getting slight hum on right channel but this would figure as psu part of board right next to toroidal, going to move into bigger case so should be much better.

 

[Rob Flinn]

gonna change the L1 choke for lower ohm version, self wind

Any chance of doing an extra pair ?

 

[Rlucas41]

Hello folks,
I have finished stuffing my boards and am ready to install them in my case... I need to order a few more things from Mouser and am curious what to order for the rotary stereo link switch and the "On, In, bypass" switch. I still have to order my bypass PB's (the ebay seller is away) and the little step-down pub to power them. Very excited to get this one up and running!

 

[Spencerleehorton]

Rob,

sure mate, i'll wind you a couple, send me over your details and i'll pop them in the post.

regards

Spence.

 

[desol]

Hello folks,
I have finished stuffing my boards and am ready to install them in my case... I need to order a few more things from Mouser and am curious what to order for the rotary stereo link switch and the "On, In, bypass" switch. I still have to order my bypass PB's (the ebay seller is away) and the little step-down pub to power them. Very excited to get this one up and running!

You can use any switch so long as it has enough positions...

 

[Rlucas41]

You can use any switch so long as it has enough positions...

Thanks desol!

Could you post a few more pictures of your build for reference please? Sometimes a picture(s) helps me 

Kindest Regards,
rlucas

 

[desol]

I've attached a pic of how I did my bypass switch. Basically, 1 pole is the 120 main and the other pole is the 12v supply main. I added a jumper so that when you move the switch from 'in' to 'bypass' 120v is always present and the unit stays on(meters, etc) whether in bypass or not....but also when you move the switch to bypass, it sends 12v to the coils on the relays(white wires) to power them from normally closed to the normally open position...which is XLR direct in to out(bypass).

The 1:1 ratio setting on my units does not account for makeup gain, so you get a massive gain boost if you turn it to 1:1 from say 5:1 heavy compression. The true relay bypass works to match heavily compressed vs dry signal levels better. Hope that helps. I'm no expert.

Makes me wonder what the point of the 1:1 ratio setting is?

 

[sr1200]

the 1:1 just gets the flavor of the transformers into the signal chain.  Mine is quite colorful so i could see someone wanting to maybe do that... but id rather squish things with it.  ;D

 

[Rlucas41]

the 1:1 just gets the flavor of the transformers into the signal chain.  Mine is quite colorful so i could see someone wanting to maybe do that... but id rather squish things with it.  ;D

Hello sr1200!
Ive finally gotten around to this build, your help with my SB4000 was indispensable and I used your build guide for the PYE! Im waiting on a few more things to arrive and then I can power this one up... You happen to have any pictures of your build?

 

[sr1200]

I dont have any gut shots of it.  Ill be happy to remove it from the rack if you need to reference something.

 

[desol]

the 1:1 just gets the flavor of the transformers into the signal chain.  Mine is quite colorful so i could see someone wanting to maybe do that... but id rather squish things with it.  ;D

The transformer option I completely understand. It's just that I'm used to other (different) units that account for makeup gain when you bypass the sidechain. I have a good bypass on this unit and I see now why someone included it in the design. No biggy....

 

[MagnetoSound]

The original units are pretty transparent, so 1:1 was just intended to defeat the compression and eliminate the need for bypass. I used these daily for years and never felt like it needed a bypass switch. If I wanted to I could just pull the return jack out of the patchbay and let the jackfield bypass the unit, but like I say it was never really something I needed to do because switching the ratio to 1:1 sounded perfectly linear to my ears.

That said, I guess the Pye trannies had nothing lacking and the signal path is really very simple, so if you're hearing a lot of colour there might be something squiffy going on ...

 

[Spencerleehorton]

Im in the final stages of the re wiring and changing the layout of my unit, need to find some other inductors to re wind L1 as well.

one question, should the output leads form the pcb to the output transformers be screened 1 core cable? or use 2 core not screened?

also ive seen someone put copper tape wrapped around the output txf, is this copper tape then put to GND?

regards

Spence.

 

[MagnetoSound]

I'd have thought the output wiring to be non-critical, but original units had single-core screened leads.

Can't comment on the copper foil, but why wouldn't you ground it?

 

[desol]

The original units are pretty transparent, so 1:1 was just intended to defeat the compression and eliminate the need for bypass. I used these daily for years and never felt like it needed a bypass switch. If I wanted to I could just pull the return jack out of the patchbay and let the jackfield bypass the unit, but like I say it was never really something I needed to do because switching the ratio to 1:1 sounded perfectly linear to my ears.

That said, I guess the Pye trannies had nothing lacking and the signal path is really very simple, so if you're hearing a lot of colour there might be something squiffy going on ...

Thanks for your reply.  I'm assuming the units are working correctly, as they both appear to function and sound very much like what I've heard the actual circuit doing, but they haven't been measured, proven, etc. They were put on a scope and a few things looked at to the best of my abilities. The oscillators and trimmers were set as per the guide(trimmers are not labeled on the board, which I thought was a bit odd...but whatever).

They sound unique to any of my other units, so I'm a bit confused with the description of transparent. As soon as I turn it on(even on light settings), I can immediately hear it; as I increase the input, it seems to handle things really well, and musically.

Apart from jump in gain I get when I switch down to 1:1, everything seems to be working normally. I have to assume(by your reply) that you 'did not' need to lower the makeup gain before switching to 1:1. Has anybody else noticed this on their units?

As far as I know, the only things that were changed(more or less) were the additional input 'mike' stage(removed) and the oscillator component 'improved'. I know that the originator of this had messed with it for years before releasing this final version, and that he had units on hand to observe, listen to, etc.

 

[MagnetoSound]

Apart from jump in gain I get when I switch down to 1:1, everything seems to be working normally. I have to assume(by your reply) that you 'did not' need to lower the makeup gain before switching to 1:1. Has anybody else noticed this on their units?

The originals have a dual-ganged, reverse-wired threshold control which decreases the output level at the same time as it increases the input level, thereby increasing/decreasing compression while keeping the overall gain at unity. Unless you are really smashing it, you don't hear that much of a jump in level when going to 1:1.

If your unit has separate input and make-up controls I guess it might explain the need for compensation, though.

When I say transparent, I mean that since the gain is at unity regardless of threshold, patching in at 1:1 should result in no change in response. I would guess that any tonal difference you might be hearing under these conditions is likely to be transformer colouration, unless something is wrong with the signal path circuitry. If the trannies have been tested for DC resistance with DC current, they might need degaussing. I remember a warning in the Pye manual about that.

 

[desol]

Ahhh..ok. That makes sense with the pots being unganged. I understood that they were separated, but I didn't connect the dots with the make up gain... it can be brutal if you're not paying attention and you switch it under certain conditions. I feel like locking that position out now, as I don't really see myself using the box in that manner.  Also thanks for clarifying what you meant by transparency Dan. I hadn't checked it for coloration at 1:1. I just powered it on, and started using it.

 

[Spencerleehorton]

Here is my layout