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

[Ilya]

I respectfully disagree.  I tried everything I could to get unity gain from the comp.  The best I could do was a 6dB loss with some pretty wild value changes.  Add to that that the output section in the 4060 schematic adds about 28dB of gain.
Best,
Bruno2000

I could get unity gain with 1:3 step-up on the output. If you're using 1:2 step-up, you'll get 6dB loss, I agree.

I played with the circuit a lot in the sim, and it's unity gain if SC operates correctly (and with 1:3 output tx). 4060 output uses another output transformer, so its apples to oranges comparison.

However, this is not my main point. I'm saying that in it's current state the osc and the following circuit is not forming the correct waveform at the base of the chopper. I think we need to concentrate on this first. And deal with the unity gain issues later.

 

[bruno2000]

I could get unity gain with 1:3 step-up on the output. If you're using 1:2 step-up, you'll get 6dB loss, I agree.

I played with the circuit a lot in the sim, and it's unity gain if SC operates correctly (and with 1:3 output tx). 4060 output uses another output transformer, so its apples to oranges comparison.

However, this is not my main point. I'm saying that in it's current state the osc and the following circuit is not forming the correct waveform at the base of the chopper. I think we need to concentrate on this first. And deal with the unity gain issues later.

Ah, a step up XF on the output............
My reply was based on no transformers at all........
Best,
Bruno2000

 

[eddie_ruff_]

Up and running! https://youtu.be/Pa7UC_Gr3_o

Trim pots are very crucial to proper setup. Here is how I think of it (even though it may not be technically right, this is what I heard/saw)

1) Compression amount is determined by a very specific range on R23. Set it just before the audio craps out or the compression sounds unpleasing

2) R52 is maxed to one side. Deals with meter zero'ing. But not as much as R48

3) R48 has a very particular sweet spot for meter zero'ing. Get it in the 0-4dB range and then crank R52 which ever way to get the meter right on zero

4) R42 wasn't doing too much for me, but I think it influenced the meter speed and how fast the meter was swinging. Nominal value is fine.

Getting both meters similar is tricky, count the turns on the pots. Also, make sure the 100ms and 3.2 s decay times are actually what the meter does, R48 will change this.

 

[desol]

I got a mail from Abe not too long ago indicating that he was getting back to it. Be really nice to see him here soon....

 

[Ilya]

Very good.

I'm still curious to see the ratios that other builders get. It's very easy to measure. Feed the signal to the compressor and set it so it just starts compressing. Increase the signal 10 dB. You should get 5 dB/3 dB/2 dB increase for each respective ratio (2:1/3:1/5:1).

Anybody? It takes just a couple of minutes.

 

[eddie_ruff_]

I used a 440Hz sine tone. I guess I would need 23db return to get a proper 5:1 for this example. I'm sure Trim Pot adjustment will remedy this ratio issue. Send and return vol are in dB.
Here are my calculated ratios:

Send Vol Ratio Return Vol Actual Ratio Channel
-24         2:1         -25                N/A                   L
-24         2:1         -25           N/A                   R
-14         2:1         -19.4       1.8:1                 L
-14         2:1         -19.4       1.8:1                 R
-14         3:1         -20.6       2.3:1                 L
-14         3:1         -21.0       2.5:1                 R
-14         5:1         -21.0       2.5:1                 L
-14         5:1         -21.8       3.1:1                 R
-14         Limit   -16.4       1.2:1                 L
-14         Limit   -17.6       1.4:1                 R

 

[Ilya]

eddie_ruff_

Thanks for your effort!
1 dB increase is too small to give any meaningfull information about ratios. You need to increase the signal by a 10 dB to calculate ratios correctly.

 

[eddie_ruff_]

I did! I started at -24dB and then went up by 10dB to get -14dB

 

[Ilya]

I did! I started at -24dB and then went up by 10dB to get -14dB

Ah, I see. For some reason I had very strange formatting on my phone and misread your table.

So the compression starts at -23 dB?
What values of trimmers did you set? (EDIT: disregard, I've found the info in your previous post)

EDIT2: Do you have a scope? Could you scope the output of the oscillator and the base of chopper without signal?

 

[bruno2000]

Ah, I see. For some reason I had very strange formatting on my phone and misread your table.

So the compression starts at -23 dB?
What values of trimmers did you set? (EDIT: disregard, I've found the info in your previous post)

EDIT2: Do you have a scope? Could you scope the output of the oscillator and the base of chopper without signal?

Here ya' go.
T/D 1uS
1V/D
Anything else while I've got it on the bench?
Best,
Bruno2000

 

[Ilya]

Here ya' go.
T/D 1uS
1V/D
Anything else while I've got it on the bench?
Best,
Bruno2000

Wow, cool! Thanks a ton!
A base of chopper would be helpful. Without signal or at the onset of compression.

What sidechain trafo are you using? 1:4 or something else?

 

[bruno2000]

Wow, cool! Thanks a ton!
A base of chopper would be helpful. Without signal or at the onset of compression.

What sidechain trafo are you using? 1:4 or something else?

Sidechain 1:4
Using the 555 so base?
Best,
Bruno2000

 

[Ilya]

Sidechain 1:4
Using the 555 so base?
Best,
Bruno2000

I mean the base of TR11 (the PN3640).

I suspect that my ratios are screwed because of the sc trafo. I'm currently using 1:2 as was suggested in another thread by someone who claimed to have measured the originals. Gonna get a higher ratio tafo and see if it changes anything. I've been messing with this for almost a week and the circuit behaves as it should. But the ratios are way off.

 

[bruno2000]

I mean the base of TR11 (the PN3640).

I suspect that my ratios are screwed because of the sc trafo. I'm currently using 1:2 as was suggested in another thread by someone who claimed to have measured the originals. Gonna get a higher ratio tafo and see if it changes anything. I've been messing with this for almost a week and the circuit behaves as it should. But the ratios are way off.

None,
Best,
Bruno2000

 

[bruno2000]

I mean the base of TR11 (the PN3640).

I suspect that my ratios are screwed because of the sc trafo. I'm currently using 1:2 as was suggested in another thread by someone who claimed to have measured the originals. Gonna get a higher ratio tafo and see if it changes anything. I've been messing with this for almost a week and the circuit behaves as it should. But the ratios are way off.

Lots (limit)
Best,
Bruno2000

 

[bruno2000]

I mean the base of TR11 (the PN3640).

I suspect that my ratios are screwed because of the sc trafo. I'm currently using 1:2 as was suggested in another thread by someone who claimed to have measured the originals. Gonna get a higher ratio tafo and see if it changes anything. I've been messing with this for almost a week and the circuit behaves as it should. But the ratios are way off.

Only a week?
Best,
Bruno2000

 

[Ilya]

Only a week?
Best,
Bruno2000

Ok, This puts things in perspective....

Thanks for pics!

 

[bruno2000]

Ok, This puts things in perspective....

Thanks for pics!

My pleasure.
Hooked up to the AP.  Anything else?
Best,
Bruno2000

 

[Ilya]

My pleasure.
Hooked up to the AP.  Anything else?
Best,
Bruno2000

Not anything important I can think of right now. Maybe only this - what THD reading are you getting in the 1:1 mode?

 

[bruno2000]

Not anything important I can think of right now. Maybe only this - what THD reading are you getting in the 1:1 mode?

About 0.2% at 0 dBu out
About 2% at +20 dBu out.
w/extra Neve gain stage (+10 dB)
Best,
Bruno2000