Aleph P v1.7 Muting Circuit

pb1234 · 23rd February 2010, 01:01 AM

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......

Nelson Pass · 23rd February 2010, 02:17 AM

Maybe it needs a load. Is the preamp gain stage connected?

pb1234 · 23rd February 2010, 02:30 AM

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.

pb1234 · 23rd February 2010, 03:45 AM

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.

Nelson Pass · 23rd February 2010, 06:17 AM

Ta Daa....

23rd February 2010, 01:01 AM	#1
pb1234 diyAudio Member Join Date: Mar 2009	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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23rd February 2010, 02:17 AM	#2
Nelson Pass The one and only Join Date: Mar 2001	Maybe it needs a load. Is the preamp gain stage connected?

23rd February 2010, 02:30 AM	#3
pb1234 diyAudio Member Join Date: Mar 2009	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.

23rd February 2010, 03:45 AM	#4
pb1234 diyAudio Member Join Date: Mar 2009	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.

23rd February 2010, 06:17 AM	#5
Nelson Pass The one and only Join Date: Mar 2001	Ta Daa....

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