RE: Schematics for 01A,26,27,56,76 aso transformer preamp

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Posted by wpod (A) on May 27, 2007 at 06:02:05

In Reply to: RE: Schematics for 01A,26,27,56,76 aso transformer preamp posted by Rune on May 27, 2007 at 02:17:09:

If you are truly concerned with the amount of gain (or lack there of), before laying out the cash for a pair of transformers, you may want to experiment with a simple passive device (pair of Radio Shack 100k pots), to see if your power amp/s is a good match for these low mu triodes. Of the few different amplifiers that I paired the preamp with, only the Heathkit W5Ms proved to be a bad match, I had plently of gain to drive the IPC AM1027 amps as well as a pair of Dynaco MkIIIs. So far I have found the #30 tube to be the easiest to work with (less microphonic) as well as the most neutral and accurate sounding. Another thing that I learned (not soon enough) about these tubes is that the placement of the preamp too close to certain power amps can pick up hum as well. This phenomenon would probably have been noticed sooner by a more experienced builder, but it had me baffled at first. After many trials and tribulations,I finally have a preamp that is dead quiet, it wasn't easy getting there, but I learned a lot along the way. I plan on doing some "critical" listening in the upcoming week/s so that I can finally decide on which tube to optimise the circuit for. I'd like to make the preamp more versatile to use several tube types, but from what I have learned here, I'd be better off picking one tube and sticking with it. Right now I'm leaning towards the #30, the low filament current draw (.06 ampere) makes it very appealing. If I settle on one of the other tubes that I've yet to try (01A,112A), I'll post my impressions. Have fun, wpod

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Follow Ups Full Thread

Topic - Schematics for 01A,26,27,56,76 aso transformer preamp - Rune 03:24:38 05/26/07 (12)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - nl 03:58:03 05/27/07 (2)

Thanks nl! - Rune 02:05:14 05/28/07 (1)

RE: Thanks nl! - nl 04:38:21 05/29/07 (0)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - wpod 05:05:30 05/26/07 (8)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - Rune 02:17:09 05/27/07 (5)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - wpod 05/27/0706:02:05 05/27/07 (2)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - Rune 02:10:23 05/28/07 (0)

30 tube - andy evans 07:12:01 05/27/07 (0)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - andy evans 04:37:23 05/27/07 (1)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - Rune 02:17:49 05/28/07 (0)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - JANDG 05:55:46 05/26/07 (1)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - andy evans 07:10:57 05/26/07 (0)

Follow Ups

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - wpod 05/27/0706:02:05 05/27/07 (2)

RE: Schematics for 01A,26,27,56,76 aso transformer preamp - Rune 02:10:23 05/28/07 (0)

30 tube - andy evans 07:12:01 05/27/07 (0)

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