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Old 9th November 2012, 11:17 PM   #1291
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Originally Posted by AudioSan View Post
that's correct albertNL
Thanks, AudioSan!
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Old 10th November 2012, 08:50 AM   #1292
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I do not totally agree.
Several of us, including me, found a bias current as high as 1.2 to 1.3 amps per leg using stock values.
1 amp per leg (2 amps total) is enough though. (think about dissipation)
By curiosity, you should measure the bias current on your amp.
Anyway, your amp is running a little too warm IMO.(You tell 33 above ambient)

Last edited by bobodioulasso; 10th November 2012 at 08:55 AM.
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Old 10th November 2012, 01:05 PM   #1293
ide2003 is offline ide2003  Indonesia
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there are 2 trim pots on my aleph J, one for biasing and one for dc-offset
but for Albert, don't worry too much right now, just enjoy you new amp
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Old 10th November 2012, 01:44 PM   #1294
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For information: Trim R8 for offset, R27 for bias.( lowering R27 lowers the bias.)
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Old 12th November 2012, 09:16 PM   #1295
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I don't know how to measure the bias (is probably mentioned somewhere in this long, long thread) but I don't have any trimpots anyway. Any adjustment would have to be by taking out (or adding) resistors. I think I will leave it as is for now

I finally got the feet on today. Metalwork is not easy for someone in an electric wheelchair , I can tell you.

The amp is sitting on the bench and has been cooking for a bit under an hour with the top plate in place. DC offset is at 39mV (and still slowly decreasing) at speaker outputs (input shorted) and temperature is 59 Celsius (ambient + 33) at the hottest point I can find on the heatsinks. Seems OK to me

I will leave it for another hour and check again. If it is still OK I hope to be able to test the sound tomorrow.

Thanks again everyone for all your help, and of course a big thank you to Nelson for your generosity. It makes it possible to build and own such beautiful amps!

Albert

PS It is quite possible that I will be asking simple questions in other threads in the future, as I think I may have been infected by a diy-amp virus that is prevalent on this forum!
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Old 12th November 2012, 09:28 PM   #1296
Zen Mod is offline Zen Mod  Serbia
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if you find it little on hot side , you can always arrange something like this :


Babysitter for Papa's Koan
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my Papa is smarter than your Nelson !
tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb ; Papatreasure
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Old 12th November 2012, 09:44 PM   #1297
ide2003 is offline ide2003  Indonesia
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Albert, why wait for tomorrow? or is it past midnight in Holland?
you know what they said, midnight listening is best, until your wife calls you that's is

ZM, that babysitter is one of the fuglyest I ever seen..ha ha, might need one for my hot SIT
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Old 13th November 2012, 01:02 AM   #1298
Marra is offline Marra  United Kingdom
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It is quite possible that I will be asking simple questions in other threads in the future, as I think I may have been infected by a diy-amp virus that is prevalent on this forum!

There is no known cure
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Old 13th November 2012, 01:45 AM   #1299
6L6 is offline 6L6  United States
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Marra -

That is fantastic news! Welcome to the initiated.

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Illustrated Build Guides - Pass F4 - Pass B1 - Pass F5 - Pearl 2 - O2 HPA - Hagerman Bugle 2 - Pass Aleph J - Me at BA '13
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Old 13th November 2012, 05:50 AM   #1300
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Quote:
Originally Posted by albertNL View Post
I don't know how to measure the bias
There is no hurry but, for info again:
One measures voltage across source resistors of the power mosfets.
Knowing voltage and resistor gives current when applying the ohm's law.
As there are two output pairs, the current found is to multiply by two.
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