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i'm on a roll... the kgsshv

kevin gilmore

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Amb only sell to builders of their amp. I had to do the matching myself and was pretty lucky. Followed : http://www.diamondst...ching_jfet.html

guess it depends on the circuit but in gilmore's amps I match for Vgs at the current used in the circuit, rather than Idss. i found this makes more sense.

Edited by justin
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I'd take 50 2sa1486

It really sucks how so many of these transistors get discontinued.

I just went in for 50 pairs of matched sk170/sj74 as well. Didn't realize they were getting so rare. Hopefully I can get some decently matched quads in there

Edited by cobra_kai
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The transformer is a beefier 150VA model, it uses a screen and the 420 V windings are now capable of continuous current @ 250mA.

The psu is standard 450V, for the amp boards I changed R8 and 9 from 180ohm to 113ohm, simply by parallelling 300ohm over the existing 180ohm resistors which saved lifting the amp boards of the heat sinks. I was going to dabble with the third stage, but chose to leave it, I was concerned about not being able to get the boards to balance. As it is I can get both boards under 1 V, but cannot get down to the ~ 0 V where I was before, not that is matters, just worth mentioning. As for heat, there’s not much difference, runs slightly warmer overall.

Listening I found higher frequencies have opened up, sounded really good to my ears and definitely worth the effort.

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Thanks Victor,

There’s not really much to see, however here is what I did. Either side of the LED in R8 and R9 positions the default 180ohm resistor is still in place I simply paralleled a 300ohm resistor over the top. This changes the value to 112.5ohm.

The calculation mA is derived;

1.7v - vbe junction (.7) /112.5 ohms == 8.8mA

(see Kevin’s post #1893 for detail)


Thanks Kevin and Birgir for all your help with this.

Edited by johnwmclean
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