Reverb problem with DRRI

[rockman627]

I had a similar problem with a JC120 recently and I suppose the fix is similar. I seem to get plenty of reverb, but the dry signal is really "in front of" the wet signal. I'm thinking increasing r25 will reduce the dry signal. Am I on the right track? It's quitting time now so I'll get back to this on Tuesday.
Fender-65-Deluxe-Reverb-Schematic.pdf

[Helmholtz]

I seem to get plenty of reverb, but the dry signal is really "in front of" the wet signal.

Don't understand the problem.
Amp has "plenty of reverb", but still not enough?

The reverb control adjusts the mix between dry and reverb signal, so why change the circuit?

[g1]

It seems that with the JC120 you did opposite what I had thought, and actually increased the dry signal proportion (by reducing R61 value).
https://music-electronics-forum.com/...em-with-jc-120

[Chuck H]

I've never heard of anyone having trouble with the amount of reverb available from the standard Fender circuit. That said...

New reverb tanks can leave a lot to be desired. And it's random. "the dry signal is really "in front of" the wet signal." could be something to do with that particular reverb tank. Maybe try another one before making circuit mods. And...

I wouldn't increase R25. It's already a very high value. If another tank doesn't sound better and all circuit parameters check out there may still be a work around or two. But I wouldn't increase the R25 value.

[The Dude]

I've never heard of anyone having trouble with the amount of reverb available from the standard Fender circuit......

Me neither. Especially the DRRI! I've actually had to tame the reverb in a few of those because it was so overwhelming that it went into feedback. The ones I've worked on could easily get into Dick Dale territory. I wonder if there isn't something wrong with the amp in this case- bad/low gain tube, plate resistor raised in value, broken tank spring, or something of the sort.

[g1]

There was a run of weird Ruby tanks in some Fender DRRI and Custom Deluxe reverb, PRRI, and possibly others. Even Ruby has since changed the spec. on those tanks. They measure lower than usual DC resistance at the tank output, like 50 ohms or so, and don't sound the same. They have the Fender part # 063064 sticker over top a Ruby sticker that reads RRVL2AB1C1BV4.
The new Ruby tanks with that number now read the traditional 200 ohms or so at the output.
Both tanks, however, are shorter decay time than the original accutronics types (going by the number).

[rockman627]

Considering that describing sound is subjective and difficult, i will try anyway. With most reverb amps, i perceive there to be 1 signal which is a mix of dry and wet. On this amp (and the JC120 I mentioned), it appears like 2 separate signals: 1 dry and one wet. As you turn up the reverb, the dry level remains the same and the wet signal gets more swishy but does not increase in level giving me the perception of a dry signal in front of the wet signal. I am under the impression that the reverb pot gets a pure reverb signal from the tank and sends out a pure signal, level adjusted by the pot, and gets mixed with the dry signal just before feeding V4b. That's why I thought something in the mixing stage was off. But I am going to try a new tank first because even if that's not the problem, we always could use a spare tank.

[Chuck H]

As you turn up the reverb, the dry level remains the same and the wet signal gets more swishy but does not increase in level...

That sounds wrong. It is, however, just as you describe regarding the dry signal not changing with reverb level. That is indeed how the circuit works. But the reverb volume should increase with the control. Not just it's swishiness. It sounds to me like you're not getting much LF from your reverb circuit? That might make it seem aenemic and dominated by the dry signal. Reverbs don't have a lot of LF anyway but usually enough to sound like a proper echo of the signal.

A weak reverb driver tube might do this. A bad transducer in the tank might do this. A failed cathode circuit or a bad reverb transformer could also be responsible. So that's pretty much anything in the reverb circuit I guess. But the bottom line is that if you can't get big, surfy reverb or damn close to it there's probably something actually wrong with it. Because that's how this circuit always sounds when working correctly.

EDIT: Go to any store, shop or find a local private seller for any Fender BF/SF style circuit. Go and test drive it to get a bead on how your reverb should sound. This is the most ubiquitous tube reverb circuit in the world and they all behave basically the same.

[g1]

I still think it is instructive for you to look back at what happened with the JC-120 (post #3 above). Somehow, increasing the dry signal was perceived as better sounding reverb.
What you did there would be the equivalent of decreasing the R25 (3.3Meg) here, as far as I can tell.

[Chuck H]

Yep. The dry wet mix was changed to increase dry singnal on that JC-120 while nothing at all was chaged regarding the reverb signal.

[rockman627]

Ok, I came in and took out a Reverb tank from a different DRRI, and that solved it. I looked at the problem tank and it has a wire disconnected. In the past, I would get no reverb whatsoever if a wire was disconnected. I don't know why this case was different, but I soldered the wire and the tank now works correctly.

[Tom Phillips]

... In the past, I would get no reverb whatsoever if a wire was disconnected. I don't know why this case was different, but I soldered the wire and the tank now works correctly.

Without hearing what your amp sounded like with the problem and knowing which transducer in your tank was disconnected it's difficult to speculate. It is possible, although highly unlikely, that the signal that was getting through was due to capacitive coupling between the broken wire and the recovery transducer terminal. The proximity of the wire and the terminal would need to be really close. That would not work if the break was at the drive transducer because the power transfer would not be adequate. Another possibility is that the recovery transducer connections were intact and the reverb springs were picking up acoustic energy from the speaker.