Aleph 5 DC offset and bias adjustment

Bertie · 20th December 2002, 11:23 AM

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?

rwagter · 20th December 2002, 12:12 PM

Did you really search. I asked because it has been covered really recently. B ut here are the links:

Aleph5....it works!!!
DC offset / Bias setting for Aleph 2
Upping the bias on Aleph 2

RALPH

Nelson Pass · 20th December 2002, 03:47 PM

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
place.

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.

Bertie · 22nd December 2002, 02:49 PM

Yes I did search,

and thanks very much to Nelson for the reply.

20th December 2002, 11:23 AM	#1
Bertie diyAudio Member Join Date: Sep 2002 Location: UK	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? __________________ Bertie

22nd December 2002, 02:49 PM	#4
Bertie diyAudio Member Join Date: Sep 2002 Location: UK	Yes I did search, and thanks very much to Nelson for the reply. __________________ Bertie

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20th December 2002, 12:12 PM	#2
rwagter diyAudio Member 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: Aleph5....it works!!! DC offset / Bias setting for Aleph 2 Upping the bias on Aleph 2 RALPH

20th December 2002, 03:47 PM	#3
Nelson Pass The one and only 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 place. 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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