Aleph60 input stage mistake! Pilot error - diyAudio
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Old 3rd November 2005, 06:39 PM   #1
diyAudio Member
Join Date: Aug 2001
Default Aleph60 input stage mistake! Pilot error

Hey guys, it's been 3 years since I completed this Aleph5 with an Aleph60 front end. It's been giving me beautiful and reliable sound all this time except for a few symptoms.

1. Turn off pop in R channel on power-off
2. Hum in L channel - that decreased in level when the IN- was connected to 'GND' (made a mistake here... see pic below)
3. When driven by a strong drive preamp output, audio signal leaks to the R channel when amp is powered off.

It's time to go back and figure out what's wrong and the answer was obvious when I looked at my schematic done in Eagle.

Question is: Are these schematic mistakes to blame for the symptoms I've been seeing? Which is the first to fix and why?

What is the purpose of R0? Would it work to just remove R0 and short the connections?

Thanks for all your help,

PS - Those who downloaded and used my PCB design back then will experience the same issue... Sorry!
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Old 3rd November 2005, 09:35 PM   #2
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Join Date: Oct 2003
Peter Daniel brought this topic up here. The schematic your showing does seem incorrect, maybe it was an earlier schematic. I recently D/L the A60 pdf, looks like there may have been some changes.
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Old 5th November 2005, 01:27 AM   #3
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thanks for the link mega-amp!

the schematic i uploaded here is a doctored version of the one in the service manual to show the schematic entry error i made when laying out my PCB.

based on Nelson's answers, i think i've figured out a quick fix... will post the results once i've done some tinkering
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