Deluxe reverb shrills too much with overdrive pedals

[Jesse Rev]

Weird problem with vibrato channel in 65 deluxe reverb reissue:

- Guitar plugged to vibrato channel amp = perfectly normal nice clean sound.

- Guitar plugged to overdrive pedal then to vibrato channel amp (both imputs 1 or 2) = it shrills in an annoying way. Im not talking about that common extra bright sound in deluxes due to C10 capacitor for vibrato channel. I mean a really shrilling and dirty and thin overdrive sound. It happens since the last jam, so that amp sounded perfectly before. Only happens with overdrive pedals, not with wha, univibe... reverb and vibrato amp effects work perfectly...

- Normal channel is working perfectly, plugged to amp or using pedals.

Have you ever seen something like that and know which could be the problem?

[xtian]

First make sure the speaker isn't exhibiting cone cry. Play your amp thru an external, known good, speaker cabinet.

Next, swap preamp tubes for the vibrato channel to make sure it's not the tube sounding bad when its overdriven.

[pdf64]

Fender BF/SF circuits tend to give a nasty tone if pushed at high volume settings with the bass control too high.
The tone stack can put out massive bass, which becomes too much for the power amp / speaker to cope with.
Hence Tube Screamer type ODs, which have a lot of bass cut, are well matched to them.

[Chuck H]

The other responses are accurate, but do I interpret from your post that the system was working to your satisfaction once upon a time, but now it doesn't? And if that's the case, are you certain nothing has changed about the circumstances? Gain setting? Playing volume? Guitar used? So far the Q has been approached as "What to expect from your gear and how to use it properly". Which should be a friggin book available at every guitar store But I still don't know by the post if the amp is broken or misunderstood.

[pdf64]

Yes, has it previously worked ok with that pedal and those control settings (amp, pedal & guitar)?

[Jesse Rev]

Yeah, the system has been working fine for a long time and suddenly started to fail.
It only happens plugged to vibrato channel, so normal channel is still working fine. That's what makes me think the speaker is OK too... Definitely, the amp is broken, not missunderstood

I removed a couple of pedals from my usual chain to avoid any bad element in the middle. I made sure to set a "sweet point" for the pots, clean for amp and medium overdriven for pedal (as I use to play seeking a blues-rock-hard rock sound... Allman Brothers, etc.). Then I checked again:

Les Paul =>> Rockett Animal pedal (setted: volume pointing 9 o'clock, gain 12 o'clock, bass and treb 12 o'clock and snarl switch off) =>> Amp (setted: volume 3 in the knob numbers, bass and treb 5... reverb and vibrato 0).

Rockett was swapped for a Klon Centaur clone to dismiss any pedal failing.

I swapped preamp, power and rectifier tubes to test it but the problem persists.

Remember the problem comes only when overdrive pedal is switched on. And the amp sounds perfectly its clean tone when pedal is off.

[Chuck H]

Ok. Two things to consider. One is that there is a tad more gain in that channel due to the reverb recovery stage. Incidentally, that's one reason many players that don't even use reverb or trem use the "vibrato" channel and just turn the reverb to zero. That added gain may be part of the formula causing your problem.

The other thing is that the vibrato channel is opposite is phase in relation to the "normal" channel.

Now, I can't think of much about tube amp behavior that would make the amp change from 'fine with a dirt box' to 'shrill and thin with the same dirt box' but with no difference to the tone without the dirt box. I'm thinking it could still be something outside the amp itself. Like your guitar pickups may have become slightly microphonic and are only reacting with the one channel because of the differences.?. That's a stretch, but it seems possible.

So at this point it's important to be very vigilant in details. Is there ANYTHING else going on? Something like a volume drop, the reverb bleeds through or the trem is slightly on or ticks even though both of those effects are set to zero? Are you sure the no pedal tone is just as it's always been? Are you using the footswitch now, but you weren't before? Are you A/B switching the channels, but you weren't before? Any differences or odd behavior at all that also occurs with the problem might help to isolate it.

[Chuck H]

Oh... Here's a schematic of the amp.

[Jazz P Bass]

Best to keep in mind the OP's question: "Have you ever seen something like that and know which could be the problem? "

[Jesse Rev]

So at this point it's important to be very vigilant in details. Is there ANYTHING else going on? Something like a volume drop, the reverb bleeds through or the trem is slightly on or ticks even though both of those effects are set to zero? Are you sure the no pedal tone is just as it's always been? Are you using the footswitch now, but you weren't before? Are you A/B switching the channels, but you weren't before? Any differences or odd behavior at all that also occurs with the problem might help to isolate it.

I swapped a couple of overdrive pedals and different guitars to check if any of it was the problem. It persists plugging the footswitch jack or unplugging it.

Best to keep in mind the OP's question: "Have you ever seen something like that and know which could be the problem? "

Never seen something similar before in any other amp.

[g1]

Do you have a signal generator or other signal source that you could try?
If you can inject a high strength clean sinewave that would tell you if something is just collapsing due to signal strength, or if it actually requires a distorted signal for the fault to occur.

[J M Fahey]

Well, the amplifier obviously broke and must be troubleshooted.
Somehow you either lost Bass or gained a lot of Treble; both are acceptable with clean signals but can make any squarewave (distortion) sound buzzy or shrill.

That, IF the amp is used *exactly* the same way as before.

If you went from stage or rehearsal room to bedroom, 99% distortions shound shrill or tinny but thatīs a combination of human ear poor bass response at low volume and overboosted highs cused by bright caps.

[copperheadroads]

the stock jensen speaker (C12K i believe) has horrendous fizzy breakup .

[Chuck H]

According to Jesse the problem didn't always exist and the clean tone is the same as it was. It is only when a any distortion pedal is used that the tone "shrills" and it didn't do it before under the same exact circumstances.

I can't think of any problem that should cause this without any other symptoms. But I asked a few questions about specifics and certainty and they were answered to the affect seen above. I have no clue.