Aleph P v1.7 Muting Circuit - diyAudio
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Old 23rd February 2010, 01:01 AM   #1
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Default Aleph P v1.7 Muting Circuit

I built the power supply for the Aleph P v1.7 preamp which works fine, except when I connect the muting circuit. When I do, the regulated 60v immediately jumps up to the unregulated level of ~85v - with or without the relay coils connected. I have tried numerous fixes. I can't find anything similar in a search of the posts. Has anyone had a similar problem?

In tests with the mute circuit removed, I found any resistance in parallel with the D-S of the main IRF610 (Q23) has the same effect, i.e. connected like R110 and R111 in the differential part of the mute circuit......
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Old 23rd February 2010, 02:17 AM   #2
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Maybe it needs a load. Is the preamp gain stage connected?

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Old 23rd February 2010, 02:30 AM   #3
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Thank you very much for the reply. No, I'm testing the power supply on it's own, stand alone, prior to connecting to the preamp....which actually isn't assembled yet.
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Old 23rd February 2010, 03:45 AM   #4
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Thankful for such a simple answer. Indeed the power supply needs to be under load. With the regulated output loaded by a 6k resistor the PS behaves beautifully. I wasn't courageous enough to actually hook it up to the main board until it tested right. PS, I'm building the Aleph P v1.7 to drive the Mike Rothacher designed Circlotron.
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Old 23rd February 2010, 06:17 AM   #5
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Ta Daa....

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