Deluxe Reverb: slight distortion at low volume

[pecorporation]

You're right,g-one, my bad.

[Jonny toetags]

So I went through the amp again, cleaning all connections, going over solder joints (fixed a couple), even cleaned all the sockets again.
It's still doing it.
Now I have to wait for my capacitors to come in.
I'll reply back after I change them....the saga continues...

[Jonny toetags]

Hey guys,
It took a few weeks but I finally got my new caps in.
I replaced all my filter caps, but I still have the same issue.
Checked all connectors.....

Any ideas?

[Jazz P Bass]

Get your hands on a scope.

[Chuck H]

Cold bias induced crossover distortion ?

[Chuck H]

Just a thought... If there is a low signal passing with the volume at zero there may be a DC condition that is fluctuating. This would be the low, distorted signal. Does it do this even with the guitar volume at zero? When this happened to me it was a bad preamp tube. I know you said you tried different tubes but try another different tube in the first preamp position. Also check for DC on the input jack.

[Pedro Vecino]

I'm noticing slight distortion a low volume (between 1 and 2) on a Deluxe Reverb. It happens on both channels
What would be the possible culprit: a preamp tube? power tubes?
I should note, it's a Deluxe Reverb Reissue that was fully re-tubed after purchase.

Deluxe Reverb requires a careful bias adjustment to sound clean and good. A low adjust creates a patina of unmusical distortion probably more noticeable with low volume settings. If you have 425 volts should read 24/25 mA. through the plates of the 6V6 (10 watts dissipation at idle). If the pair of 6V6 lacks symmetry complicates the problem.
I say this as a possibility.

[Jonny toetags]

Just a thought... If there is a low signal passing with the volume at zero there may be a DC condition that is fluctuating. This would be the low, distorted signal. Does it do this even with the guitar volume at zero? When this happened to me it was a bad preamp tube. I know you said you tried different tubes but try another different tube in the first preamp position. Also check for DC on the input jack.

I will check that when i get in.


I'm not sure if this helps diagnose anything, but one thing I noticed is that while I have the same issue on both channels, the volume of the' bleed through noise' on the vibrato channel is louder than on the normal.

[Jonny toetags]

Deluxe Reverb requires a careful bias adjustment to sound clean and good. A low adjust creates a patina of unmusical distortion probably more noticeable with low volume settings. If you have 425 volts should read 24/25 mA. through the plates of the 6V6 (10 watts dissipation at idle). If the pair of 6V6 lacks symmetry complicates the problem.
I say this as a possibility.

I biased it after retubing it.
I must admit, I haven't checked the bias since this issue started. I assume an amp's bias wouldn't change after 3-4 months of inactivity?

[Pedro Vecino]

The adjust should stay the same but this is a good time to confirm it, and with it the symmetry of both tubes. If the effect comes from this it may have gone unnoticed at first.

[Jonny toetags]

Just a thought... If there is a low signal passing with the volume at zero there may be a DC condition that is fluctuating. This would be the low, distorted signal. Does it do this even with the guitar volume at zero? When this happened to me it was a bad preamp tube. I know you said you tried different tubes but try another different tube in the first preamp position. Also check for DC on the input jack.

It doesn't do it with the guitar volume at 0.

[Jonny toetags]

The adjust should stay the same but this is a good time to confirm it, and with it the symmetry of both tubes. If the effect comes from this it may have gone unnoticed at first.

The bias is idling at 23mA.
I also tried another pair of powertubes and I still have the issue.

[Jonny toetags]

Something else i noticed:
-when I'm plugged into teh vibrato channel and the volume is at 0, when i move the volume knob on the normal channel i hear a scratching if i turn the.
This also happens if i plug into the nrml channel and move the volume on the vib ch.

Been playing with this thing all afternoon..I'm about to call it quits and either use the warranty (although I'm sure they wont touch it now that i changed the filter caps) or gut it and rebuild it completely.

EDIT: Went back to the preamp tubes and it looks like V1 AND V2 could be the culprit.
I put all the stock GT tubes back in and it wasn't doing it. So then I went back to my new tubes one by one and noticed the noise come back with V2 and V1.
What would cause both of these to go at the same time?

[Chuck H]

They're just bad tubes. If they're "pulls" there's a reason they were pulled. If they still have gain and aren't grossly microphonic many people would sell them as useful. If they're NOS I could only speculate that they were part of a bad run. Which might explain why they were never sold when they were made, but not how they ended up being sold as NOS. If they're Russian tubes all I can say is that I've had many bad ones right out of the box.

The only tube I've had do what you describe was a Telefunken smooth plate pulled from an old stereo amp. That tube also made it so I still had the low distorted signal with my guitar volume turned to zero!

[soundguruman]

Yeah I know this amp.
The plate resistors in the preamp should be replaced.
If it were mine, I would replace all the resistors in the audio path w/ good ones.
This is what makes it sound fuzzy and buzzy...cheap resistors.
It's not really the tubes at all.

Also, the output should be biased on the hot side, that helps a bit.

Recommend F&T caps for the power supply filters. Dump the Illinois Capacitors, they make it sound awful.

You play a note on the guitar and at first it sounds normal, but as the note decays...and the volume drops...
You hear a "bzzzzzzzzz" (if you listen closely) kind of distortion, at the end of the note decay.

That's really what it's been, resistors in preamp for sure. I've had several w/ the same symptoms.

Once again, this is not verifiable with a sine wave and O scope. You won't see this in a standard bench test.
ONLY testing with a GUITAR, will you actually detect this problem. LISTEN very closely, with a GUITAR.