Odd Harmonics Question

[ndemattheis]

I have a 50w Sundown Head. I have been noticing odd, out of tune harmonics when playing single notes. This occurs when using clean or overdrive and occurs on both channels. I have tried changing cabs and guitars and I think I have isolated this problem to the head. What can be causing this? Is this common? Fixable? Thanks.

[cap47]

May be a preamp tube going micro!

[WaltC]

very common with under-filtered B+ or one or more failing B+ filter caps. Is it only or more obvious when playing around the 9th fret or so?

[ndemattheis]

I didn't take notice of where on the guitar it was happening. I will have to report back on that.

[mark norwine]

caps. yep. You've got signal on the B+ rails.

[Blue Strat]

Ring modulator

[Studio91]

I hate to hijack the thread, but I'm curious as I have a similar issue that I've been wondering about.

Why the question about the issue only around the 9th fret? This is exactly my issue(9th fret E). Does this lead to more conclusive evidence of a failing filter cap?

[donnyjaguar]

The output section of a PP amplifier is humbucking by design so dried up primary filter capacitor(s) may not be obvious until there is signal passing through. 9th fret? I'm curious to learn too.

[Jerry Glass]

Originally Posted by Studio91

I hate to hijack the thread, but I'm curious as I have a similar issue that I've been wondering about.

Why the question about the issue only around the 9th fret? This is exactly my issue(9th fret E). Does this lead to more conclusive evidence of a failing filter cap?

The 9th fret on the E string is close to 120Hz; the frequency the power supply runs at (and the electrolytics are attempting to filter). With the frequencies being so close to one another, a warbling effect can be heard if the filter caps aren't doing thier job any more. The same effect occurs ot all frequencies but it is most noticable around 120Hz because as you overlay the two frequencies, they coinside/counteract at a higher rate.

[WaltC]

couldn't (really!!) have put it better myself <G>

[GT100]

Originally Posted by WaltC

very common with under-filtered B+ or one or more failing B+ filter caps. Is it only or more obvious when playing around the 9th fret or so?

This

Lloyd

[Studio91]

Originally Posted by Jerry Glass

The 9th fret on the E string is close to 120Hz; the frequency the power supply runs at (and the electrolytics are attempting to filter). With the frequencies being so close to one another, a warbling effect can be heard if the filter caps aren't doing thier job any more. The same effect occurs ot all frequencies but it is most noticable around 120Hz because as you overlay the two frequencies, they coinside/counteract at a higher rate.

Thanks. That makes total sense to me now. I guess it is time for some service, but that means shipping cross country. What catastrophe would follow if I wait too long and continue gigging an amp with a failing filter cap?

[TweeDLX]

This maybe... (clip courtesy of Mr. Adam "Satellite Amps" Grimm)

[Jerry Glass]

Originally Posted by Studio91

I guess it is time for some service, but that means shipping cross country.

Where do you live? I'd bet there is a tech someone would recommend in your area.

[Studio91]

I live in the middle of Idaho in the mountains. Closest tech is in Boise, three hours away. I don't like that tech. It's easier on my mind just to send it to Carr as he's guy is on top of things. It's just a shame to go without for the 4-6 weeks turn around.

If anyone knows of someone great in Salt Lake City or Boise, do share.