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FDP Forum / Amp Mods, Repairs, and Projects / 94' Twin weak reverb

Willie D

USA

Apr 24th, 2012 09:08 AM Edit Profile Print Topic Search Topic
I'm not sure if the reverb on my 94' "Evil Twin" has gotten weaker since I last played it over a year ago or if recently playing a pair of Silverface Twins has colored my idea of what a reverb should sound like - but right now I'm not very happy with the depth of the reverb on my Twin.

There is a bit of a hiss with the reverb up at 10 so I thought maybe it was a bad tube but I tried swapping out the send and receive tubes and nothing changed. It still could be tube related but for now I'll assume it's not...

I took the reverb unit out of the bag and nothing looked grossly amiss but I'm not really sure if I'd recognize a problem short of a broken wire.

I've read the stock unit isn't great but I'm wondering if there is any way to alter it to improve the sound of the reverb. What is mechanically different on "good" reverb units? Seeing how rudimentary these things are I wonder if there is any way to alter one to make the reverb deeper

Any ideas on improving mine?

willie
Contributing Member
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Walton County, GA.

We Fixee good, you like!
Apr 24th, 2012 07:23 PM Edit Profile Print Topic Search Topic
Not alot to offer initially but the tank could be bad or have a number of things that could degrade it. It should be a 4AB3C1B...though a 9AB3C1B might help it a little. Be sure to check the value of R56...should be 1 meg or better. You said you already checked V5 and V6...so not too much other to easily check out. This circuit is not the typical Leo Fender type design so there are some quirky things that could be dodgy in the amp that would take qualified eye on it to find.

willie
musicmenders.com

Willie D

USA

Apr 29th, 2012 10:22 PM Edit Profile Print Topic Search Topic
Thanks for the tips!

So I swapped a few tubes around and the hiss turned into a rattle. Moved a few more around and the rattle and hiss mostly went away.

The amp is probably due for some new tubes. It still has the OEM tubes but for one 12ax7 that went bad a long time ago and one 6v6 that I dropped.

I think now that the reverb is the same as it ever was. I hadn't been playing at volumes I was able to use at my old address - but still it's not as deep and dreamy as the Silverface Twins I've recently had the pleasure to play. (Why those amps get so much flack on the web I just don't get...)

I still wonder if anything can physically be done to the stock unit to improve depth/length of reverb? Stretching out the springs maybe? I suppose I'll probably just have to bite the bullet and get a different unit.

Anyhow, a re-tube may be in the future. I'm wondering if the tube positions on the link below are correct? Is there a tube in that layout that doesn't directly affect the audio; i.e. can I get away putting a bum tube in one spot like you supposedly can on a Twin Reverb?

Also I'd like Channel 2 to be less fizzy at volume. Would a lower gain tube in the v3 do that? I'd like to tame that channel a bit but not affect the Vintage Drive.

Thank you for the help, I do appreciate it.
94' Twin Tube Layout

FDP Forum / Amp Mods, Repairs, and Projects / 94' Twin weak reverb

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