biasing up the mini-crescendo kind of construction.. - diyAudio
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Old 29th June 2002, 01:32 PM   #1
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Arrow biasing up the mini-crescendo kind of construction..

will i gain anything except heat?...the bias runs @ 100mA right now...
my output trannies are running hot as is, about 50C , should i change them (2sk1058/2sj162) before raising the bias?

any comments or experience are welcome!
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Old 29th June 2002, 08:19 PM   #2
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in my experience with the Hitachi fets they gain a lot in sound quality up to 180-200mA per device. I run 3parallel pairs@a bit over 300mA a piece.

Is your heatsink 50 or are the fets this hot? I have run for manny years with heatsinks of 50 without problems.

raising bias from 100 to 180-200 would be asking for trouble though when the sinks are alrasdy 50.
The best thing would be to change the sinks or leave it as it is.

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Old 22nd July 2002, 01:06 AM   #3
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The higher you bias the output MOSFETS the better it gets.
I tried this before but the heat dissipation is too much.
You need a lot bigger heatsinks if you want to use 200ma or more.
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Old 22nd July 2002, 03:16 PM   #4
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Lightbulb ok...

Now the amps runs @50C stable, measured at the hetsink,
just nearby the transistors.
The bias is now 200mA, and i noticed a slight sonic improvement..
Thank you all for the help!
-another Q, i believe the DC at the output is a little too high, how should i adjust this in a proper way? maybe incorporate a potentiometer at a tactical spot in the circuit? 80mV doesnt sound very good to me, id like it to be much lower, help please!!

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