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

[MagnetoSound]

The shunt goes across the meter (between + and - ). The series resistor (maybe there is one already if you have a trimmer) goes ahead of it. Or between - and ground if you prefer.

By adjusting the two values you should be able to set a zero point and a sensible deflection range.

I cannot offer values, sorry. They will depend on your meter more than anything, but the shunt will probably need to be close to the resistance of the meter coil.

 

[Spencerleehorton]

Ok so we are probably talking about putting in 100R trimmers then and having a twiddle right?

 

[desol]

That's how I got my meters to zero, by turning r52...as it didn't seem to affect the sound of the unit. I tried dialing it down and up and listening while compressing heavy/soft, etc. Nada...didn't do anything that I could hear at all....but of course, that's subjective.

That's why I mentioned earlier in this thread that I wish he had labeled the trimmers on the board(obviously, there's other logical ways to deduce what does what, I just don't know how to do it).

All of my other trimmers were pre-trimmed to the suggested values and left, and it's been good ever since. I'd still like to know what's what tho...

 

[Spencerleehorton]

Yes that’s what I have found, R52 doesn’t effect sound but seem to have the most influence on the meter position, but with mine I can’t adjust it anymore as it’s fully one way, so I need to change something to allow a bit more range to be adjusted?

 

[MagnetoSound]

Ok so we are probably talking about putting in 100R trimmers then and having a twiddle right?

That sounds like a fair starting point.

 

[Spencerleehorton]

I wondering whether TR13 has effect on the meter position, as I have same values in both channels but one meter very nearly lines up and the other doesn’t?
I might test both and see if they are different?

 

[MagnetoSound]

Looking at the schemo I have on file, I think TR12 is the one you're concerned with.

I've just spotted that there is a 1k5 resistor (R65) which is connected across the meter lines.
I would try reducing the value of this resistor, in order to bypass more of the drive current away from the meter. This might bring R42 into range.

Transistor matching between channels is never a bad thing, though.

 

[MagnetoSound]

Or increase R67.

 

[Spencerleehorton]

top darts dan, hopefully i'll get a minute and try this! will report back.

 

[Spencerleehorton]

HI All,

I have just changed R65 to 1k trim pot and this works well to dial down the meter to zero, so if you need to this works great!!

 

[MagnetoSound]

Glad that fixed it for you.

 

[Spencerleehorton]

Yes thank you very much Dan.

 

[desol]

We still don't know what all the trimmers do, or at least I don't. Namely R52.

 

[Ilya]

We still don't know what all the trimmers do, or at least I don't. Namely R52.

R52 is decay time as marked on the schematic. It works on my unit just fine. Although it may not work correctly with 555 oscillator.

 

[Rlucas41]

I have calibrated the oscillators and and balanced the channels in/out... I was able to use R52 to zero my meters but do feel indeed it adjusts decay as well...  but it works for me. This thing sounds smooth and tight, it can really squish but is also smooth on the vocal tracks I have tried it on and it does indeed sound great on acoustic guitar... but it is especially groovy on the drum buss! I don't know that it will see my 2buss very often but it will get used in every mix from here on. it is very quiet too! Now on to the next build

 

[MagnetoSound]

R52 is definitely for calibrating DECAY time, but does have a slight effect on the idle position of the meter.

On the original Pyes, the meter always tends to sit about half a dB or so above zero when DECAY is properly adjusted. Just perceptible on an original unit, but possible to ignore once you know about it.

I strongly suggest calibrating the meter to zero first using R42 (and R65), with R52 (DECAY) all the way down. Then, to calibrate R52 go to the longest setting and calibrate recovery time if you can arrange a suitable test signal (drum samples with reverb tails of known duration are good for this). Alternatively, you can calibrate at the 100mS setting for the shortest undistorted recovery time (pick a signal with good LF content) if you feel the shortest setting is the most crucial.

 

[desol]

Hey, thanks for pointing that stuff out guys. Actually, I think I remember seeing the notes for the trimmers at some point on the schematic, now that someone mentioned it. I'll dial those decay trimmers up a few turns next time I have it open Magneto..thanks for that advice.

 

[vitopower]

Is there anyone who is willing to describe the process and parts required for building the oscillator transformer?

 

[Ilya]

Is there anyone who is willing to describe the process and parts required for building the oscillator transformer?

The transformer is basically several turns of wire around a ferrite ring. You need to find the ring with the correct permeability to get the osc frequency you want. This can be done with some experimenting.

 

[vitopower]

Thanks, Ilya!