Question about Volume bleed thru

Archived from groups: rec.audio.tech (More info?)

"JRUBBO770" <jrubbo770@aol.com> wrote in message
news:20040605155515.27551.00000527@mb-m05.aol.com...
> I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6
push/pull
> output. It is a three channel amp each with a Vol. control (1 meg). With
the
> three Vol. controls turned all the way down, a moderate signal will still
pass
> thru to the output on any channel. What is the cause of this? Also a
signal put
> into any channel will bleed thru to the other channels. There are no other
> problems with the amp. Your technical help is certainly appreciated.
Please
> email at: jrubbo770@aol.com Thanks

Is this a new problem, or has it always done this?

Archived from groups: rec.audio.tech (More info?)

Robert Gault <robert.gault@worldnet.att.net> wrote in message news:<40C329F5.3000105@worldnet.att.net>...
> JRUBBO770 wrote:
>
> > I have a 1950s Stromberg Carlson PA integrated tube amp with a 2-6L6 push/pull
> > output. It is a three channel amp each with a Vol. control (1 meg). With the
> > three Vol. controls turned all the way down, a moderate signal will still pass
> > thru to the output on any channel. What is the cause of this? Also a signal put
> > into any channel will bleed thru to the other channels. There are no other
> > problems with the amp. Your technical help is certainly appreciated. Please
> > email at: jrubbo770@aol.com Thanks
>
> Did you buy this amp as new and did it always have this problem? If so
> it is a bad design and may not be correctable.
>
> If the problem just started, look for visible signs of change on the
> circuit board. Are all tubes in good condition?
>
> What signal can you hear with all volume controls turned off? Is it
> source material plugged into the amp or radio frequency interference? If
> the sound comes from something plugged into the amp, is any input worse
> than the others? Do all channels bleed equally into the others or is
> there a worst case setting?
>
> The problem seems to be located after the volume controls in the amp
> rather than the preamp section, based on your description. That suggests
> bleed through via the power supply. But you need to collect more
> information to narrow down the problem to some small group of amp parts.

If this is the amp of which I'm thinking, or a similar model, there is
no circuit board, it's all point to point. Also it's a 3 input single
channel (speaker) output, and I'm not sure if there are 3 separate
pre-amps or just one with 3 potentiometers feeding it. It would
probably be cheaper to replace this unit with something brand new than
to have it worked on if a shop can be found that knows what they're
doing on old tube circuitry, however if the original poster wants to
invest in sentiment and nostalgia I'd start by checking all those half
century old capacitors.