Strange Amp Problem...Anyone else experience this? Solution?

[BlueFrankie]

Thanks for looking. Any help on this is appreciated.

I had been diagnosing for a long while a harsh ringing overtone which I believed was coming from my guitar. I had ruled out all the usual suspects and finally admitted I needed a tech's help. Tonight there was an unexpected twist. I plugged a friends guitar into my amp and discovered that it too produced the same harsh ringing overtone through my amp. The problem chords are the same on both guitars and the pitch of the overtone/overtones is the same on both. obviously, the amp is now the prime suspect.

What is going on? Who else has had this experience? Most importantly, how can I fix it?

Gear:
Washburn WI66v Korean Import circa 1990
Korean Fender Tele Circa 2000's
Mesa Boogie Lonestar Special (problem persists through both channels, with reverb on or off, with effects loop in use or not, presence knob low or high)

Thanks

[CapoFirstFret]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Sounds like tube rattle/issues to me. I'd try it with a new set of power tubes before I touch anything else.

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Thanks. It's not rattle. Problem has persisted through several tube changes. (total re-tubes). I'm certain the sound is a ringing overtone especially since it causes enharmonic beats (sometimes called interference beats) depending on it's context within a chord or interval.

[FuseG4]

Re: Strange Amp Problem...Anyone else experience this? Solution?

have you tried the amp/noticed the problem with different speakers/cabs?

[LLL]

Re: Strange Amp Problem...Anyone else experience this? Solution?

old can caps... (e.g. filtering) can cause nasty overtones.

[TwilightOdyssey]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Have you tried the same guitar with a different amp? The inverse?

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Have you tried the same guitar with a different amp? The inverse?

Thanks, I have tried the same guitar with a blackstar ht club 50 and a Marshall JVM 410. I can't get those amps to replicate the problem. I assumed that this was due to the nature of the Lonestar Special having that chimey el84 vibe. My thinking went like this, "The guitar has a harsh overtone problem, which is especially exposed by an amp like the Lonestar Special, but masked by the EL34 style amps." Not saying I know anything about amps, but that's where my mind was at.

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

old can caps... (e.g. filtering) can cause nasty overtones.

The amp is ten years old. Could an amp of that age have the capacitor problem you suggest? Can you unpack that particular issue further? Thanks

[Outshined]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Try with a different speaker or even another cab, without the main speaker(s) connected. I've experienced a faulty speaker causing cone cry, which was a high pitched overtone, making certain leads etc sound ugly.

Sent from my SM-G930F using Tapatalk

[GoldenVulture]

Re: Strange Amp Problem...Anyone else experience this? Solution?

The amp is ten years old. Could an amp of that age have the capacitor problem you suggest? Can you unpack that particular issue further? Thanks

Ten years is about where problems in capacitors may arise, a lot will last another five to ten years.
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I had a similar problem to yours a while back, with one of my amps. It was more like a distortion of overtones on certain notes and chords.
It turned out to be a bad pot in the tone control section. It took me a while to nail it. It has a Treble pot and Mid and Bass pots.
It was the treble pot.

[devastone]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Sounds like it is caused by specific harmonics, I agree that it could be the caps, but I would start with mechanical stuff, check all the screws, pots, and knobs to make sure they are tight, especially screws that mount the speaker.

[mxaniac]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Have you tried this from different positions with respect to the speaker? Just trying to rule out interaction between the guitar and speaker.

Have you swapped all the tubes or just the power tubes? I had a preamp tube making a strange sound on certain notes regardless of the octave.

Is there anything you always have plugged in like a tuner or an equalizer that was overlooked that might be the problem?

Do you have a schematic of the amp? Someone adept at analog circuitry (I am not) might be able to point out which caps would affect certain frequencies. You'd have to provide input on specific notes causing the issue.

On a fundamental level I keep coming back to the thought that to have this occur you either have to have a forcing function at the natural frequency which would be more of a mechanical problem, or the amp is gaining up certain frequencies an octave above the input. Other possibilities might certainly exist but that's all that comes to mind for me.

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Ten years is about where problems in capacitors may arise, a lot will last another five to ten years.
---------------------------------------------------------------------------------------------------------
I had a similar problem to yours a while back, with one of my amps. It was more like a distortion of overtones on certain notes and chords.
It turned out to be a bad pot in the tone control section. It took me a while to nail it. It has a Treble pot and Mid and Bass pots.
It was the treble pot.

That's interesting because I have one pitch (doesn't matter where on the fretboard I play it) where I get increased distortion and the fundamental sort of disappears into the harmonic content. I wonder if the two issues are related.

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Try with a different speaker or even another cab, without the main speaker(s) connected. I've experienced a faulty speaker causing cone cry, which was a high pitched overtone, making certain leads etc sound ugly.

Sent from my SM-G930F using Tapatalk

I will try through another speaker and report back.

[BlueFrankie]

Re: Strange Amp Problem...Anyone else experience this? Solution?

Sounds like it is caused by specific harmonics, I agree that it could be the caps, but I would start with mechanical stuff, check all the screws, pots, and knobs to make sure they are tight, especially screws that mount the speaker.

Will do. I'll let you know what happens. Thanks