In Reply to: Phono preamp - odd capacitor question - picture posted by PeterI on March 19, 2007 at 09:06:53:
Pete,Can you provide a topside picture of your preamp? I'm pretty sure that I've got the "same thing" 'cept some of the parts seem to be spaced a bit differently and mine uses "King" brand oil caps.
If we've got the same unit then your's has only a 1/2 wave rectifier (1 diode) with 60 Hz ripple - changing this to a full wave bridge will more or less double your filtering. Also the tube heaters aren't referenced to ground nor to a positive source. Adding a "synthetic center tap" - that is, two matched 100 ohm resistors in series across the heaters with the mid point where the resistors are soldered to each other either connected to ground or to a positive source through a voltage divider should help your noise level a bit.
Otherwise there really isn't much more you could do with this chassis 'cept perhaps add a choke to the power supply bolted onto the output side - but you'd have to experiment to determine whether the choke radiated more hum than it eliminated.
Rob
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Follow Ups
- Re: Phono preamp - odd capacitor question - picture - Rob Mercure 10:33:29 03/20/07 (4)
- Re: Phono preamp - another picture - PeterI 12:36:46 03/20/07 (3)
- Re: Phono preamp - another picture - Rob Mercure 13:55:04 03/20/07 (2)
- Re: Phono preamp - another picture - Ron Oehlert 06:28:43 03/21/07 (1)
- Re: Phono preamp - - PeterI 07:54:48 03/21/07 (0)