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i'm on a roll... the kgsshv

kevin gilmore

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  • 3 weeks later...

Hello, everyone.

Need some advice, does anyone know a supplier in Australia or Oceania that produce a toroidal transformer for the KGSSHV for Australian 240V voltage?

Got an uncompleted KGSSHV from the states and there's only 1 117V primary winding so I can't bridge 2 117V to make 234V

20180131_215336 (Large).jpg

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  • 1 month later...
  • 2 weeks later...

This is probably a ridiculous question (I know little about circuits and DIY), but doesn't the 580v bias come from the power supply? If I'm only changing resistors on the output stage to increase the current, why would a rebias be necessary? This is for a 500v off board version, which I'm just trying to increase the output current on. Someone tell me it's a bad idea :)

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The 580V voltage is for the headphones - this is sometimes called biasing the headphones. When you change the resistors on the output stage you have to adjust the currents in the output stage so that the output sits at zero volts with respect to ground - this is referred to as biasing the output stage. These are two separate things that are not related to each other except that they are sometimes referred to with the same term - "bias." 

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Just to be clear:

  1. Turn off and unplug amp for 5 minutes
  2. Change the output bias resistors
  3. Turn on amp and leave on for 10 minutes
  4. Ensure the + and - for each channel at the Stax plug is as close to 0V as possible by screwing the Balance screw on the respective channel board.
  5. Ensure the + at the Stax plug and ground (will need to find a ground lead on chassis) for each channel is close to 0V by screwing the Offset screw on the channel board.
  6. Done?


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I was able to parallel the resistors to an effective 125R and double checked it using my multimeter.

I checked the Balance and Offset voltages before and after the procedure, and they were essentially the same (~0v). I didn't have to adjust the pots at all. Did I do something wrong?

The amp sounds essentially the same, with the volume being similar at the same positions on the knob. ?

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  • 4 weeks later...

At lower volumes, do balance and offset voltages that are farther away from zero make a bigger difference vs higher volumes?

For example, my 500v kgsshv is usually ~2v away from 0 for balance and offset. If the left channel is negative 2v and right channel is positive 2v, would that be audible at low volume and not higher volumes, or is it always 4v/500v difference at any volume, which is less than 1% between the channels?

Edited by powertoold
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