Fender 65 DRRI - Is this normal? Reverb still sounding/ringing when turned off

[GuerillaGrobi]

Hi folks, I need some help with my amp,
I recently bought a used 65 DDRI (from 2014) and modified it mainly with the help of Rob Robinettes pages and PsionicAudios videos.
Changed filter caps, removed the bright cap, moved grid stoppers to output tubes/valves, added a PPIMV (Trainwreck Type 3 with a 100K log Pot and a Bypass Switch) and a Hum Balace Pot. Also changed the European RoHS Tremolo circuit without the “tremolo-roach” to a circuit including the optocoupler/roach. Everything works great now. Tremolo und Reverb sound really good, its noise-wise really quiet and I love it.

But...
one litte thing annoys me still.

In the Vibrato Channel I still hear very little reverb ringing after stopped chords when the reverb is turned off. It is not guitar related and the the normal channel has no reverb ringing at all , so I don't think it is the reverb tank itself. Checked the grounding on the reverb footswitch and switch jack. No resistance there, all of the reverb signal should be lead to ground when the switch is on (reverb off).

Is this little reverb a normal behaviour? I don’t have access to another DRRI. I would prefer a dry/no reverb channel when reverb is turned off. Does anyone have advice for me or know any mod to dry up the vibrato channel.

Before:

After

 

[corliss1]

No, that doesn't sound normal. To confirm if that's really the case, if you pull the reverb cables, does the noise stop?

 

[GuerillaGrobi]

Thx corliss, that’s a good point. It stopps with the cables pulled. It’s also no real “noise” just little reverb, does not sound bad at all

 

[corliss1]

My guess would be one of, or a combination of the mods performed, is leaking juuuuuust enough of the reverb signal to cause this, if you didn't notice it before those mods were done.

 

[Pete Farrington]

Maybe the valve in V4, or C16, is bad, thereby allowing crosstalk between the V4a and b circuits.

 

[GuerillaGrobi]

Maybe I also messed something up when changing R32

 

[GuerillaGrobi]

Swapped V4 to another 12AX7A without effect. Will check c16 and r32. Thx for your input

 

[GuerillaGrobi]

Maybe the valve in V4, or C16, is bad, thereby allowing crosstalk between the V4a and b circuits.

Hi Pete, hi corliss1. Checked C16, R32. Looked normal, also changed them. Still little rest reverb.
Then used a 12AT7 on V4. No rest reverb! Tried other 12AX7 Tubes - again rest reverb. Seems to be a crosstalk problem between 4a and 4b with the hotter AX. So I'll stick with the 12AT7.
Cheers and Thanks again for answering!

 

[Michael Smith]

Hi Pete, hi corliss1. Checked C16, R32. Looked normal, also changed them. Still little rest reverb.
Then used a 12AT7 on V4. No rest reverb! Tried other 12AX7 Tubes - again rest reverb. Seems to be a crosstalk problem between 4a and 4b with the hotter AX. So I'll stick with the 12AT7.
Cheers and Thanks again for answering!

Very neat work on your modifications! Congratulations.

 

[zook]

Did you turn it off with the footswitch?

 

[Pete Farrington]

In the Vibrato Channel I still hear very little reverb ringing after stopped chords when the reverb is turned off.

Did you turn it off with the footswitch?

See above excerpt from post #1
Note the the reverb switching arrangement is different in the TI than the original black and silver panel designs.

 

[Snfoilhat]

If the gain of the tube was the variable that changed the behavior, then it seems like signal beaming across space in the lead dress. It could be moved around with a chopstick to find an arrangement where the wet signal stops leaking in

 

[GuerillaGrobi]

Very neat work on your modifications! Congratulations.

Thx!

Did you turn it off with the footswitch?

Yes. With the footswitch and also by grounding the jack directly.
BTW The valve/tube change works really good.

Does anyone have any concerns regarding changing valve types in V3 and V4 (12AX v. 12AT v. 12AU) e.g. current-wise?

 

[GuerillaGrobi]

If the gain of the tube was the variable that changed the behavior, then it seems like signal beaming across space in the lead dress. It could be moved around with a chopstick to find an arrangement where the wet signal stops leaking in

Good point. Tried a little with no effect but not thoroughly. Next time I open the Amp/case I’ll put a looper with stopped chords and test again.