Distortion issue – question about bias

[MWJB]

...also maybe try a lower mu preamp/input tube, cool off the bias see what happens at 30mA?

What kind of signal voltage are you getting from the Hagstrom, compared to the other guitars?

[Alex R]

it couldn't be fret buzz could it?

[Ronsonic]

Suggestions? Anyone had the same issue with a new guitar and vintage amplifier. Possible fix..? Ehh... Bump...

The differences between old and new guitars are minimal. Yes, there are more high power pickups than there were 40 years ago, that's about it.

If turning it down cleans it up, then that's that.

If this particular amp dislikes that particular guitar there isn't much to be done about it.

[MWJB]

If you want the amp to work with all the guitars, I agree with Ronsonic. But, if the Hagstrom is the primary guitar to be used with the amp, then change a few bucks worth of parts, rather than a guitar, or amp.

Guitars can put out 100mv to nearly a volt, this has a knock on effect all down the line, especally at the input triode.

[überfuzz]

Mhmm... I did try to lower the (out) volume on the guitar. It seemed to ease down the distortion. However, the tonal change is very drastic, it gets very muddy. I suggested a different set of strings, to start with. Nr two, a different set of pick ups. Numero 3 some amp tinkering. I'll try to convince the owner with all good advices you posted here. Thanks folks!

Off topic, slightly: Normally a guitar changes the tone depending on how the volume pot is set. Why is that, is it due to how there wired or some physics I'm yet to grasp..?

What do you get if you drop a piano down a mining shaft?

[kg]

basically at any position other than 0 or 100, the pot introduces series resistance to the "downstream" wiper node.

that, working against the cable capacitance, pushes the inherent RC low pass filter's frequency lower.

[Jazz P Bass]

In one of my earlier posts I questioned just how high of a volume the amp was running at.
It went unanswered by the OP.
If the amp is running just at the onset of clipping with the "older" guitars and the "new" guitar has hotter pickups, well then it will clip.

[Tom Phillips]

I don't believe that you mentioned the amplifier model. If this amplifier has both normal gain & low gain input jacks (Such as the classic Fender #1 & #2 inputs) try plugging the guitar that is causing the problem into the low input jack.

[überfuzz]

Update, I've played the amp again. It seems as if the power tubes are breaking up in a edgy fashion. Can be noticed with other guitars. (Could be that they're showing signs of ageing, or bad manufacturing. The owner showed me a live clip where he plays the amp with the same guitar causing it to break up some violently.) We had no quad to use as test replacement, but I think I'll try a set and report back to you folks.

Could anyone point out a 6l6gc tube that break up late and smooth, I believe the proper term is: a hard 6L6GC

[Jazz P Bass]

Get the amp back on the bench & try to duplicate the "breaking up in a edgy fashion".
You should be able to see this issue on the scope if it is the tubes.
If you can see it, good. Then you can track down which specific circuit is at fault.
If you cannot see it then the problem just may be the output transformer.

[überfuzz]

Hmm. The amp is not on my bench, not even in my tinker den. I think I'll try a different set of tubes before front the new about a possible out put transformer break down.

Thanks!

[überfuzz]

Up date
I haven't really done my 'home work'... School's taking to much time at the moment. I wanna play when I get down to a rehearsal studio. But I can't find any strange voltages in the amp.

Anyhow, I had the opportunity to play the amp again. The tubes mounted are Ruby tubes labeled: 6L6GC-M-STR. Could anyone suggest a set of tubes that would give a later break up, possibly smoother. (Talking about it we came to the conclusion that the issue most likely appeared after retubing, and then later playing with a new guitar.)

Info
The amp is a Fender Twin reverb, used by a comp guitarist that don't like crunchy break up. What tubes should I suggest. He won't go for top $$. (I told him that I heard that 6P3S tubes from Russian could be a good pic then. Please comment that to.)