eliminating hiss?

[yunger]

hi, i have major hissing in an amp i built and i know where it is coming from but i don't know why or how to fix it. the preamp is a typical cascading triode configuration like this: input-->v1-->tone-->vol-->voltage divider-->v2-->pi. the hiss is coming from somewhere between the voltage divider and the pi. i've replaced all surrounding resistors w/ tested carbon films and reflowed all surrounding joints. i've tried a ton of different 12ax7 tubes. nothing is helping. can anyone think of something else i can try?

[Structo]

Try a lower gain tube in V1 like a 12at7.

http://thetubestore.com/gainfactor.html

[yunger]

Try a lower gain tube in V1 like a 12at7.


tried that and also 7025s. no dice. bypassing the voltage divider helps but then i have no headroom....at all.

[SatelliteAmps]

Can you post a picture or an actual schematic of how it is wired? If this is a home-brew design it is hard to say exactly what might be wrong without knowing what all the parts are in the circuit.

[Structo]

Is this a long tail pair PI?
Do you have the typical voltage divider after the PI like the 220K/220K?

[yunger]

i don't see how to attach files. here's a link to another forum that i posted the question w/ pdfs. maybe a fresh set of eyes here can spot something.
thanks.
david

http://music-electronics-forum.com/showthread.php?p=99661#poststop

[donnyjaguar]

Try replacing the 10n capacitor and checking the 2x 100Ω resistors on the filament leads.

[SatelliteAmps]

Try a .022uF after the volume control, before the 220k.