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Old 16th May 2013, 10:06 PM   #11
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Here the same problem and the same solution :-)

My Pass Labs Aleph-P 1.7 DIY Project
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Old 17th May 2013, 09:25 AM   #12
biju55 is offline biju55  India
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Are you using separate power supply for each channels ? .
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Old 17th May 2013, 09:46 AM   #13
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No, i have two mono PSU´s but only one is working...
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Old 17th May 2013, 03:43 PM   #14
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Ok , i have fixed the bug today with the 221R in the Input before the Z-diodes and the problem is gone.
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Old 17th May 2013, 11:34 PM   #15
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Yes this is the way i done at my pre

I had the 221Ohm resistor before the 10k but this is only a matter of taste.

hope i could help you
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Old 18th May 2013, 03:14 AM   #16
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I have not seen an occasion where the Fets oscillate with 221 ohm source
resistors right on the Gates and after the Zeners, but I take it as read
that there might be signal sources which could oscillate into the zeners,
so perhaps 221 in series before the zeners also should be tried.

Are you also loading the outputs with the 4.7K to ground?

At what output voltage is the circuit clipping? Is it symmetrical?

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Old 18th May 2013, 06:56 PM   #17
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Loaded outputs are R49 and R64 in the schematic?
Yes i have 4.75k there.

Do you have in the orginal aleph p some resistance before the zeners (if R5/R6 is bridged) to prevent signal sources oscillate into the zeners?

Is only for interest
because i`ve done nothing in a different way as described in Service manual and wondering why this should work in a orginal aleph p and by my clone not?

how to find out at which output voltage the circuit is clipping?
If it is clipping
(maybe its only drive signal sources into insanity )

thanks for your help
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Old 18th May 2013, 07:23 PM   #18
Gyuri is offline Gyuri  Hungary
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Perhaps you may use an oscilloscope and a sine wave generator.
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Old 20th May 2013, 07:40 PM   #19
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@ Nelson

Thanks for helping me... ok this is a possibility that the source is oscillate.
The output is loaded with R49/R64 4.75k to ground and it is asymmetrical working. But current i haven´t an oscilloscope which is working now.

Is it excluded that the Aleph is clipping?


Chris
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