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Old 22nd May 2003, 09:24 PM   #1
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Question Dumb Question on Bias Aleph amps

I am sure this topic would have been discussed before but I couldnt find anything that addressed my exact question -

Does changing the bias on an Aleph amp (specifically the Aleph 3) affect the sound quality (not power output) in terms of transparency, bass, imaging, etc in any way? If so, what are the typical noticeable differences ?

The aleph 3 heatsink is running at 50C per channel (after about 4 hours of playing) and the transistor case is at about 55C. I think I have room to push it to another 7 to 10 degrees and wanted to check if only the output power is affected when bias is adjusted or whether there is any difference in musicality of the amp.

thanks in advance
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Old 22nd May 2003, 10:34 PM   #2
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Actually, I'm thinking about the idea of being able to push the bias way way down to lower power consumption and heat for times of non-critical listening, (say when my 4 yr old using the hi-fi or my wife is using it for background music whilst vacuuming)
I think I read somewhere that adjusting R19 will affect bias level.
Any comment on this Aleph heresy..?
And if possible suggest values for R19- or do I use a trimpot and record values for later substitution with switches and fixed resistors.

Regards from down under.
george a
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Old 23rd May 2003, 01:03 PM   #3
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Try reading the "Top ten ways to a better Aleph? " thread.

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Old 23rd May 2003, 07:32 PM   #4
MikeW is offline MikeW  United States
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The higher the value of R19 the higher the bias.
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Old 23rd May 2003, 07:48 PM   #5
Yonnat is offline Yonnat  France
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Default Standby solution

Hi all,
for George A,

I have include on my PCB a relay wich divide R19 value in the half, on the simulation there is no probleme but I haven't try it in real, I hope I find time next week to realise the PCB, the relay will be drived by a switch on the front of the amp and by the thermal security too, so if the amp becomes too hot it will automaticaly turn on standby.
Hope my idea can help you.

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Old 30th May 2003, 11:50 PM   #6
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Hi Yonnat

Thanks for reply.
I might try it on my Hafler DH200's prior to going too far into aleph

george a
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Old 1st June 2003, 05:55 PM   #7
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[QUOTE]Originally posted by MikeW
[B]Or leave it out altogether.
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