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Old 20th December 2002, 11:23 AM   #1
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Join Date: Sep 2002
Location: UK
Default Aleph 5 DC offset and bias adjustment

Sorry if this has been covered elsewhere but I did try and I couldn't find it.

I'm just finishing assembly of my Aleph 5 clone monoblocks and all appears to work fine on the bench.

Two questions, what level of DC offset is typical or acceptable on the output and ho can I adjust it if it's wrong?

Secondly I have read Nelson saying that Aleph 5's work better with higher bias curent. Assuming I have the thermal capacity in the sinks how can I adjust the bias up?
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Old 20th December 2002, 12:12 PM   #2
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rwagter's Avatar
Join Date: Jul 2002
Location: Netherlands
Did you really search. I asked because it has been covered really recently. B ut here are the links: works!!!
DC offset / Bias setting for Aleph 2
Upping the bias on Aleph 2

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Old 20th December 2002, 03:47 PM   #3
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Join Date: Mar 2001
To answer the questions anyway,

about 50 mv is my standard for DC offset in Alephs. If
you need to trim it you can do so in a number of places,
but adjust the the Source resistance in the current source
which biases the differential input transistors is a good

Yes, you can increase the bias easily enough using the
resistor which feeds the Base of the NPN transistor on the
positive current source. I forget the number, but its the one
which goes from the Base to a capacitor which is charged
by a resistor to the positive supply.

Simply removing this will up the bias without any other
alterations needed.
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Old 22nd December 2002, 02:49 PM   #4
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Join Date: Sep 2002
Location: UK
Yes I did search,

and thanks very much to Nelson for the reply.
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