Twin Reverb Question

[n8wood]

I picked up a silverface 74 Twin Reverb recently (w/ master volume). When I plugged my effects into it I noticed that my two overdrive pedals produced a slight midrange static-like sound going through the amp. When plugged into another amp, the sound was barely audible, it was present but it blended with everything well. I can't figure out if it's the amp or if that's just the pedal tone coming through. The pedals are a Keeley Rat and a Keeley Blues Driver, my Russian BMP sounds fine.

 

I think it has the original tubes in it (Sylvania) so I'm wondering if that could be contributing to it. What do you think it could be?

[JerryP]

Blown speaker.
Jerry

[n8wood]

Are you sure? Everything else sounds great through the speakers. I can crank it clean or with distortion and I do not hear that midrange static.

[The Boogie Man]

I wouldn't go swaping speakers just yet. Sounds like a preamp tube may be the problem. First thing I would do is check all the tube connections, make sure they are clean, spray some tuner cleaner in them or on the tube pins and work them in and out a few times and be sure they aren't arching due to a loose pin, tighten any pin sockets that look lose. See if you have a bad tube sometimes tubes can test good on a tester but have other problems you can't test for. A noisy tube or grid leakage can cause problems, a microphonic tube can be hard to test for it's often a process of elimination.

[JerryP]

Try plugging the amp into an external speaker cab and see what happens. You can gently push the speaker cones from the back of the amp and see if you hear the voice coil dragging. If you're getting a raspy harsh sound when you overdrive the amp I'd look at the speakers. You're description leads me to believe that's what you're hearing.
Jerry

[Loghead]

I hate blown speakers.

[Picker]

Hmmm... not sure what you're hearing there.

If the Russian BMP sounds find I wouldn't think it is the speakers. I have a 70 Twin and use the Keeley BD2 and TS pedals and haven't run into this.

Maybe a bad cable?

Preamp tube?

The pedals will drive the tubes harder... my guess would be a pre tube.

[n8wood]

I tested with an external cab and heard the same noise which leads me to believe it's the tubes (or caps). I dropped it off tonight for tube replacement and possible cap job.

Thanks for your help.

[tlbonehead]

Originally posted by JerryP Blown speaker. Jerry

A little bit of VC rub maybe?

[The Boogie Man]

Originally posted by n8wood I tested with an external cab and heard the same noise which leads me to believe it's the tubes (or caps). I dropped it off tonight for tube replacement and possible cap job. Thanks for your help.

 

 

 

It's a good amp, worth investing a few dollars in it's up keep, I still own my '75 I bought new and it's never been any trouble. No matter what anyone sez' your have one of the best amps Fender ever built.