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Old 30th January 2006, 06:43 PM   #1
ppesa is offline ppesa  Croatia
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Join Date: Jan 2006
Location: I. lukacica 16 Zadar
Default Problem with Aleph 2

Hello.


My name is Predrag Pesa and Aleph 2 is my 3-hird pass work.
After 50 hours work I have no words to describe the sound,
apsolutily magnificent. On the 57 celsius, with measuring on
PCB in the tolerance, this is wery well worked amp.
So where is the problem.
When I turn amp on , from one chenel comes allmost nothing,
BUT from another ,with gently"bumy" sound suck woofer in
2 or 3 mm, then hold there for 1 sec, then relesed in another
2 or 3 sec, after that everything is normal.


I used in power suply: 1KW toroid- trafo, 2 x 0,47microF MKT
40 A, 1000 V bridge
10 x 10 000 microF by Elna


I am not wery Good in electronic so simplier as you can please
help.
By the way about bias and gain for Aleph 2, which elements
control them and where are they, thanks in advance

Greetings from Croatia.

ppesa
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Old 31st January 2006, 08:44 PM   #2
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The Alephs have a small turn-on and turn-off thump, usually
around a volt or so, and that is typical. If there is no DC resistance
to the load to drain off DC, sometimes the cap in the feedback loop
will hold a slight charge, resulting in a turn-on thump larger than
usual if the amp has not been off for a while. Why one channel has
no apparent thump is probably just a coincidence of parts turning
on more synchronously than usual.

The gain of the amp itself is determined by the feedback loop. The
gain and bias of the current source is determined by the parts
surrounding the NPN transistor on the top half. You will find several
discussions on this forum detailing its operation.
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