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i'm on a roll... the kgsshv


kevin gilmore
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Or have one custom milled out of a fresh billet of alu or some nice grain revealing wood. I'm thinking nice stained wooden cheeks on my offboard KGSSHV and wooden knob, wish it could drive speakers as there is literally no e-stat in this house no more (or headphones for that matter).  :-[

Edited by DefQon
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I still haven't bothered to put a pretty knob on my kgss.  It stilll has some undersized mouser knob I had originally planned to put on a little hammond case.  Perhaps I shall make it a plan to finish this one up before you build two new amps.

 

You'd have to be quick as the chassis for those two amps are already on their way to me.  :)  All the boards are ready and have been for months so it's just a matter of doing the chassis stuff. 

 

I have so many half finished projects like this that need to be finalized.  Way too bloody many... 

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So a couple of things.  First, see this:

 

21vbjEHh.jpg

 

Looks just like all the KGSSHV's I've built but this one is different.  Aside from the 2SK170 input fets it's all in current production.  It runs at +/-400V but with just over 8mA of current and uses Fairchild FJPF2145 output devices.  Sounds pretty much indistinguishable from a +/-500V version I built as well that is pretty much identical save for the output devices and voltage. 

 

Now a couple of neat points about doing the amp this way, first of all the parts are all easy to source and secondly, so are the transformers.  Edcor has a nice dual 335V winding unit in their catalog so add a small 30VCT/25VA unit and you are set.  No need for anything custom and the PSU mods are dead simple.  Just change the zener string and the divider and bypass the voltage divider that feeds the bias supply. 

 

The second point is that I've finally given up on thePMBFJ620 fet.  Nothing wrong with it except it is just so bloody tiny that it's all but impossible to solder.  They will be removed from future versions of the boards and might be replaced with the SMD LSK389. 

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Here is a KGSSHV onboard power supply board design modified to include both normal and pro bias outputs. I moved things around a bit so that everything would fit on an 8 X 8 board. I have removed the ground plane from the second picture to make the rest of the circuit more visible.

 

 

 

dualbiasKGSSHVPS_zpsece99cd0.png

 

 

 

 

dualbiasKGSSHVPSongroundplane_zpsd743660

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