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FDP Forum / Amp Mods, Repairs, and Projects / DRRI vibrato oddity

Contributing Member

El Californio

Nov 15th, 2016 02:08 PM   Edit   Profile  

Don't use it much but lately noticed that my normally lush vibrato is weak & only begins to kick in at 5 on the intensity knob. (Used to taper in nicely.)
Also, higher vibrato intensity = less overall volume.
Any ideas for a (hopefully easy) fix? New tube(s)?

Contributing Member

Willie Nelson

Mandela Fitzgerald
Nov 15th, 2016 03:28 PM   Edit   Profile  

Remove and replace the tubes.

Also shoot some control cleaner in the vibrato control pots.

While you're in there--do the other pots as well.

Contributing Member

El Californio

Nov 16th, 2016 12:19 PM   Edit   Profile  

Thanks -goo.

Contributing Member

South Florida

Nov 16th, 2016 12:56 PM   Edit   Profile  

..but be careful poking around back there. Read the pinned article about voltage that is stored in the amp.


United States

Nov 16th, 2016 01:31 PM   Edit   Profile  

Mine has always been that way, it really doesn't even sound great until 7 on the intensity. I'd say that's just the circuit's design, I've also never been a huge fan fan of the tremolo. It's okay, but nothing to write home about. I also find the tremolo works better with high volume, it can sound kind of wimpy at low volumes.

(This message was last edited by NHILL1 at 03:33 PM, Nov 16th, 2016)

Contributing Member


too many guitars and not enough hands
Nov 16th, 2016 01:46 PM   Edit   Profile  


your DRRI just isn't right or needs some decent tubes in it

archie replace the tubes and clean as the oracle Peegoo says.


United States

Nov 16th, 2016 02:08 PM   Edit   Profile  

LeftRightOut, nothing wrong with the amp it's just the nature of the vibrato circuit, and having JJ 6v6's probably affects the tremolo's voice.

I couldn't answer why it suddenly changed to being subtle until 5, but that's the way mine is and it's no big deal. I just keep it at 7 and use it when I feel like like it.

Also, the higher the tremolo and volume cut again is just part of tremolo. The effect's job is to lower and raise volume the higher you go, the more of the effect, the more if feels like the volume is being lowered (in my amp it feels similar to compression). That said it shouldn't be super noticeable, that's never been an issue I've had. Typically you can find a sweet spot that blends the effect in a pleasant way, that's where I set mine. Doesn't seem to have much if any effect on volume.

I'd say no need to be alarmed, if you feel like it's really affecting the tone of the amp then yeah maybe do what some of the guys said, otherwise I'd just adapt and find a spot that works.

(This message was last edited by NHILL1 at 04:17 PM, Nov 16th, 2016)



Nov 17th, 2016 02:48 AM   Edit   Profile  

archiestone, if flushing the control out with lubricating pot cleaner doesn't fix it, then the symptoms, especially the vol loss at higher settings, indicate that the optoisolator OP1 (aka trem bug) is failing.

DRRI manual

(This message was last edited by pdf64 at 04:51 AM, Nov 17th, 2016)

Contributing Member

El Californio

Dec 1st, 2016 01:01 PM   Edit   Profile  

Update: I replaced the V5 tube (a 12ax7a for some reason) with a proper 7025 and it fixed the problem. Vibrato is nice & lush again. Kicks in around 3, no more loss of volume.

Contributing Member

Northern CT - USA

"We're not University material."
Mar 8th, 2017 11:53 AM   Edit   Profile  

I noticed that my DRRRI's vibrato stopped working a couple of days ago. Even with the intensity knob dimed at 10, if I got my ear close to the speaker I could hear it very faintly in the background.

So today I came out here and saw this thread. I took out the V5 tube and replaced it with a spare. Turned it on and the vibrato worked. Just for fun I swapped out the replacement tube in V5 and put back the one that was in there before. Turned the amp back on and that worked too.

I'm thinking that the V5 tube was loose. I gig with this amp a lot! And even with those tube holder thingies, they can get loose.

I like the tremolo in the amp. It's warm and subtle even with the intensity knob dimed. I rarely used the trem/vibrato, but I recently picked up a tremolo pedal and I wanted to compare it to the DRRI's trem, that's when I noticed the trem in the amp didn't work.

All good now though. FDP hooked me up again! Thanks



Are there power outlets in Heaven?
Aug 31st, 2017 02:44 PM   Edit   Profile  

I ordered a new Octo-coupler for mine because it was doing the same thing. I checked the connections on the Octo coupler, replaced the trem tube and now it works great. Got a new Octo Coupler for sale if you need one?

Contributing Member

Memphis, TN

Aug 31st, 2017 08:20 PM   Edit   Profile  

While you've got it opened up, clip that bright cap while your in there.

Look at the volume control of the vibrato channel and you'll see a 47 pf capacitor wired across the input lug and output lug of the volume control. That's the bright cap.

FDP Forum / Amp Mods, Repairs, and Projects / DRRI vibrato oddity

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