Schematic Klark Teknik Square One Dynamics

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RuudNL

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Apr 26, 2009
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Haule / The Netherlands
Looking for a schematic of a Klark Teknik Square One Dynamics compressor.
The problem is that the release time of one channel is shorter than the other ones.
Changing the release potentiometer didn't help, so I have to dig deeper.
Any idea where to find more information about this compressor?
 
Sounds reasonable.
But... where are the release caps?
This thing is filled with SMD components, so without a schematic it is like finding a needle in a haystack!
 
In all the compressors I've looked at they're right by the release pot. Could be anything from 50 nF to 1 uF

In many designs the pot is across the cap so you may be able to find it by tracing the tracks back from the pot

Nick Froome
 
I've done some reading, as I was planning on buying one of these...

The only repair story I remember (think it was on Gearslutz), ended with a faulty board. I don't know if that meant "board replacement", or a short/cut in the PCB.

However, IIRC, the symptom was exactly the same as yours.
 
I agree there must be a capacitor controlling release time. Does your DMM measure capacitance? What are the values of some of those caps? The little light brown / yellow components are capacitors. They look a little small but in theory with the right circuit they could be that small. With a scope on it running with a click track, you might be able to zero in on the right part.
 
I think I will have to investigate this problem a little more.
It seems that there is a transistor or FET in series with the release capacitor, probably for the 'hold' function of the gate.
(To prevent it from discharging during the 'hold' time.)
Also it looks like there is an OpAmp following the release stage, so this could mean that relative small capacitor values are used.
But it could be that the release circuit is more advanced than we think, because (to my surprise) the distortion on a steady tone of 40 Hz @ 10dB compression is very low, even at fast release times. Usually the distortion rises on low frequencies with a fast release time.

"The only repair story I remember (think it was on Gearslutz), ended with a faulty board."
How faulty can a board be if everything works except the release control?
Replacing the whole board is usually the quickest way to solve a problem. And also the most expensive way!
(But the service people don't care so much about that...)
 
Some thoughts / questions in no particular order

- Does the release of the faulty channel match when it's linked in stereo mode?
- Its there a chance that you are just seeing the tolerance in the release pots?
- Have you looked at the side chain signals on a pair of channels when fed from the same source?

I'd expect this design to be pretty close to the data sheet design for whatever VCA they are using, the THAT 4301?

 
I think I have found the source of the problem.
The release potentiometers are dual types ( 2 x 500 K.)
For some reason, it seems that there is a 'leak resistance' between the two sections.
(Of course the two potentiometer sections should be fully isolated from each other.)
I moved a potentiometer from the 'good' channel to the 'bad' channel, and now what used to be the 'bad' channel, functions normal.
So I think I have to replace the potentiometer with a new one.
(I didn't suspect the potentiometer at first, because it measured normal, apart from the 'leak resistance', I noticed later.
Pots are Alpha (Taiwan).
 
RuudNL said:
The release potentiometers are dual types ( 2 x 500 K.)
For some reason, it seems that there is a 'leak resistance' between the two sections.
(Of course the two potentiometer sections should be fully isolated from each other.)
I moved a potentiometer from the 'good' channel to the 'bad' channel, and now what used to be the 'bad' channel, functions normal.
Are you sure? That is very strange. I have never heard of such a thing.

500K is surprisingly large. So large that a little flux could influence things. Your pic of the board shows quite a bit of excess flux. Maybe a good cleaning would help.
 
"I have never heard of such a thing."

Well, then this is the first time!  :D

This is the type of potentiometer they used. The two resistive tracks are very close together.
Even with the potentiometer taken out of the PCB the resistive 'leak' is measurable.
In the meantime I have ordered new pots for this compressor.
 

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analogguru said:
Pretty standard stereo-potentiometer ..... beside the "D"-curve.

Yes, the "D" curve is non standard.
But I measured the old potentiometer and for me the curve is close enough to a standard log. type.
(There are no markings on the scale anyway.) 
 
Changed some potentiometers and everything now works as it should.
So: if you have a Klark Teknik Square One Dynamics, and the release control doesn't function as it should: change the pot!
(The standard 500 K. dual log. potentiometer works fine and there is almost no difference with the original pots.)
 
Changed some potentiometers and everything now works as it should.
So: if you have a Klark Teknik Square One Dynamics, and the release control doesn't function as it should: change the pot!
(The standard 500 K. dual log. potentiometer works fine and there is almost no difference with the original pots.)
Hello and thank you for your post.

I need to replace some release pots on the same device. I have searched for the Atlas 6C3 500k dual log potentiometer, but I have found none.

Can anyone advise where I can buy the Atlas 6C3 500k dual log potentiometer, or an alternative replacement? I have looked online, but I cannot see anything that looks like it would fit.

Thank you.
 
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I ordered these at the time from Mouser. (Alpha, that is.)

(Type description from the service manual in the attachment.)
 

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