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i'm on a roll... the kgsshv


kevin gilmore

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I have watched the problem I described below and it still persists. Does anyone have an idea what I could check or replace?

Since the volume of the sizzling I hear only through the headphones is dependent on the volume set on the elma stepper I am confused where it could originate? Does it make sence to assume it is not coming from the amp board, but from the elma stepper or so?

I recently noticed a strange behaviour of my good old KGSSHV which has probably been there from the beginning, but has gone unnoticed with the 009. Now I have the 007 and I had to turn up the volume a few clicks (elma stepper). I now also notice it with the 009, because I now what to listen for. During the warmup phase, one channel presents a sizzling noise which is clearly noticeable but not loud. After the amp has been running for some time, it dissappears. 

 

Does anyone have an idea?

 

I have removed the amp board and visually checked it. Also used the opportunity to add 100ohm input resistors. 

The problem still persists. The sizzling changes in volume when I turn the volume pot. 

If the sizzling originated from some arcing, changing the volume should not have and impact? yes?

There is no audible physical noise coming from the amp.

 

 

The first thing I did was checking balance and offset. Both were good. I will try my best to describe what I hear. Its a noise similar to what you hear, when you push the headphone cups against the head but less loud/less pronounced. It is not continous, more like there one second, gone the other. The volume of the sound becomes louder when I turn the stepper to increase the volume. 

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Ok I did the following test. 

 

When I removed the input wires from both boards, without grounding the inputs, the sizzling channel started sizzling well noticeable, whereas the other channel remained almost silent.

Interestingly, when I grounded the inputs from the sizzling channel it was almost quiet, with the sizzling being barely noticeable to unnoticeable. 

 

This seems to rule out the elma as a source of the problem. 

 

Does this sound more like a problem of the first amplifier stage or another stage? What parts would you start working at? lsk389 and mpsw06? below it? I don't have a scope...

Edited by insanity
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so Kerry did the analysis on this, and his name is on the board, for the next version

and I appreciate his help.

 

This is a big deal because it has essentially 1 less stage, so it runs on as little as 50

volts unreg to reg, so it generates less heat.  with 75 volts difference you can run

550V caps with 25V of margin at 450V output

 

http://gilmore.chem.northwestern.edu/kgsshvpssicnew.jpg

 

6.0 x 6.5 inches

 

if I can just find a way to get rid of the one red, you could make this as single sided

like some of the rest of the new ones.

Edited by kevin gilmore
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