Fender Twin needs help.

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

I was recently given a Fender Twin Reverb (purchased in the early 80's)
which has a very harsh unpleasant sound even at low volume. It isn't the
speakers; they sound fine when I plug them into different amps. I changed
all the valves. Both channels and all four inputs have this same crackling
overly-brittle sound.

Can anyone suggest what component (s) we could change which might be the
culprit?

Thanks,
BD
www.bdrak.com

(Don't reply by email, this address has been abandoned due to spam
overload.)

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

"Bob Drake" wrote:

> Fender Twin Reverb... has a very harsh unpleasant sound even
> at low volume. I changed all the valves.

Did you re-bias the power tubes (valves) after they were changed? I
recently changed the preamp tubes in my own mid-70s Twin, but when I put
in different power tubes I got a sound very similar to what you describe.

If the bias current isn't right the tubes can also run VERY hot and
perhaps even start a fire, so take care.

Right now I've gone back to the previous power tubes until I can find a
tech to adjust the bias for the new ones. (Should note that I don't use
this amp that much; it's just too heavy to carry around to the kinds of
places I play at the moment.)

--
Jonathan Roberts * guitar, keyboards, vocals * North River Preservation
----------------------------------------------
To reach me reverse: moc(dot)xobop(at)ggestran

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

Thanks for the info Jonathan. I'll definitely check that. I will also cancel
my original post here and post it on the guitar amp newsgroup.

BD

"Jonathan Roberts" <NotMe@NotMe.complex> wrote in message
news:fF0Wc.263$Pd2.103106@monger.newsread.com...
> "Bob Drake" wrote:
>
> > Fender Twin Reverb... has a very harsh unpleasant sound even
> > at low volume. I changed all the valves.
>
> Did you re-bias the power tubes (valves) after they were changed? I
> recently changed the preamp tubes in my own mid-70s Twin, but when I put
> in different power tubes I got a sound very similar to what you describe.
>
> If the bias current isn't right the tubes can also run VERY hot and
> perhaps even start a fire, so take care.
>
> Right now I've gone back to the previous power tubes until I can find a
> tech to adjust the bias for the new ones. (Should note that I don't use
> this amp that much; it's just too heavy to carry around to the kinds of
> places I play at the moment.)
>
> --
> Jonathan Roberts * guitar, keyboards, vocals * North River Preservation
> ----------------------------------------------
> To reach me reverse: moc(dot)xobop(at)ggestran