Early amp breakup

[Ahryn]

So I was plugged into my fender Excelsior today and I was experimenting with a few pedals at low volume (such as turning the volume knob to the lowest audible setting) and I had my ASAT plugged in, bridge pickup with the Double esquire wiring (I only call it that to avoid confusion, it's wired like an old 50-51 fender broadcaster) and with the volume on the guitar maxed out when I realized that I was getting some amp breakup or distortion.

It was not unpleasant and sounded like I had an overdrive engaged (I don't often play at levels that support natural tube breakup) My first thought was of the novelty of it but as time grew on I began to wonder if that is normal.

Can an amp hit with some powerful MFD pickups really breakup that early?

Or should I look into new powertubes as these ones must be giving up the ghost....

[louis cyfer]

even with a hot input signal, you can't get power breakup that early. if anything, it would be the v1 preamp tube. turn down the guitar volume and see if it still happens. bad caps and resistors can cause stuff like this as well. my 57 deluxe started losing headroom and break up really early, and it needed recapping.

[Ahryn]

Excellent, I woke up today thinking that if anything it would be the preamp not the power tubes that get hit by the signal.

I can turn the amp up and the guitar down and still get a clean tone it's only when the amp volume is really down and the guitar volume is full tilt does it happen.

I have a JJ 12ax7 in v1 so I think that one would be ok, I have EH 6v6s for my powertubes (a groovetube set as well ) and based only on their pedigree did I suspect it was them.

If the problem persists or evolves I'll try bringing it in for recapping, heck I still have it under warranty (thanks L&M) so I wonder if the caps go south I might be able to get it fixed under warranty.

[Elwood]

I can turn the amp up and the guitar down and still get a clean tone it's only when the amp volume is really down and the guitar volume is full tilt does it happen.

I have a JJ 12ax7 in v1 so I think that one would be ok,.

You'll find weak ones that are brand new . So you should try a quick V1 swap to be sure.
You should be able to keep a passive guitars Volume all the way up and still have overhead.

The JJ (V1) that came stock with my swart only lasted a couple months before it started to fail,
Mine would sound good for 20 minutes into warm up then went south quick.
First things First

[Ahryn]

Ahhh, I see what you're getting at.

And that is an easy thing to fix.

Maybe I'll try a Tung Sol again, I tried one and even though it sounded nice it jumped up the noise floor quite a bit.

The joys of modern tubes I suppose.

[Elwood]

That at least will let you know if the JJ is main issue .
I was gonna ask about gain structure , but I see your amp has one knob (not including the tremelo)...
LOL...so that ain't it .As long as your in using the guitar input that is.

[Ahryn]

heh, yeah.

Simplicity itself.

I usually use the mic input most of the time, it acts kind of like the second input on a normal fender.

[helle-man]

I find that speakers themselves will sometimes distort at very low volumes. For instance, EV SRO's will distort a lot at 1/2 watt, but play cleaner and cleaner as I turn up the amp.

WR

[Ahryn]

Good point!

Well even if the tube is fine I still picked up a replacement.



From what I can tell it's an old GE 12AX7 but made in Canada (yay)

The shop that I picked it up from also has one of those new orange tube testers



It tested well, and at a 7 it should be more on the cleaner side.

[Elwood]

The shop that I picked it up from also has one of those new orange tube testers

Those look stealthy , most tube testers I've seen are far from 'portable'.

I think Will is way off relating to your problem( you said it cleans up when decreasing the guitar signal strength), but it's hard to tell sometimes without hands ( or ears)-on experience.

Running pickups in series might be able to overdrive V1.
If the mic input takes a resistor out of the equation then that could account for your observations.You mentioned that's the input you normally use.
How does the sound change when using the guitar input?
How about with different guitars?

Good to have some extra tubes...good call,
elwood

[Ahryn]

Hmmm, really good points.

Unfortunately the amp is in a bit of a jam space so I won't be able to play around with it for a couple of days (darn work)

But believe me when I get my hands on it I will try out everything I can, especially now that I know what to look for and what to try.

[Elwood]

(darn work)

+1

[Ahryn]

Ding Ding, looks like Louis is the closest to being right with the caps/resistors, it's going in the shop tomorrow.

Loss of volume, distorted tone, even developed a nice little burning smell after a few moments.

Switched the tube as well, no change other than an overall tone change. When it gets back from the shop the GE is going back in, I just took it out for safe keeping (experimenting in other amps )