Bottlehead preamp frustration. Help, if possible.

Posted by gumby1 (A) on December 15, 2003 at 15:03:03

I purchased a Foreplay "whole deal" kit and hired a very experienced and competent Bottlehead kit builder to assemble the unit including an HV Snubber. I am using a Dynaco ST-70 tube amp. When the kit was complete, I was dismayed that it had noticeable "hum" although it measured within spec. Thinking there might be a problem somewhere, I sent the kit to Doc B to check out. He sent me a note back with the Foreplay stating "Hum was about 0.3mV RMS, well within spec". It was suggested that I might have a "ground loop" so I connected a wire from the Foreplay chassis to the amp chassis. The reduction in "hum" was barely noticeable and insignificant. I even hooked up two wires to make sure. I do not have a 3-prong electrical outlet at my house and use a 3-prong to 2-prong adapter to the electrical outlet. I do not know if this has anything to do with the hum or not. When I hook up my Carver solid state preamp to the Dynaco, there is not any hum. It is only when the Foreplay is used with the Dynaco that there is hum. How can I get rid of this "hum"?

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Topic - Bottlehead preamp frustration. Help, if possible. - gumby1 15:03:03 12/15/03 (16)

Re: Bottlehead preamp frustration. Help, if possible. - MarkER 05:04:30 12/16/03 (1)

Re: Bottlehead preamp frustration. Help, if possible. - bAh 14:38:42 12/16/03 (0)

Do the LV snubber too, the problem is the 2 wire plug - billwjr 04:41:17 12/16/03 (3)

Re: Do the LV snubber too, the problem is the 2 wire plug - gumby1 18:07:03 12/16/03 (2)

Re: Do the LV snubber too, the problem is the 2 wire plug - Dwaine 22:29:08 12/22/03 (0)

discouraged - Steve Culton 06:34:01 12/17/03 (0)

Re: Bottlehead preamp frustration. Help, if possible. - ezragreen 20:30:32 12/15/03 (0)

I use a ST-70 with mine - Grainger49 19:08:05 12/15/03 (2)

One more question... - Grainger49 19:40:17 12/15/03 (1)

Re: One more question... - gumby1 22:52:58 12/15/03 (0)

That can be a very difficult thing to track down - Triodeuser 16:43:49 12/15/03 (2)

Re: That can be a very difficult thing to track down - gumby1 17:07:10 12/15/03 (1)

Powervar is a brand of - Triodeuser 22:07:02 12/15/03 (0)

Re: Bottlehead preamp frustration. Help, if possible. - rockpassion 16:06:20 12/15/03 (0)

Re: Bottlehead preamp frustration. Help, if possible. - Bill Barrett 15:43:56 12/15/03 (0)

Re: Bottlehead preamp frustration. Help, if possible. - fc_harry 15:24:42 12/15/03 (0)

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