Motorboating? (amp related of course)

jony

jony

New member
What do you guys mean when you say an amp "motorboats"?

Cuz something like that is happening to mine right now and I need some suggestions.

Basically the symptoms are that once I sustain a note (especially the low ones) at the end of that note comes this what seems to me a motorboat like sound along with the guitar signal. Its pitch changes when I bend the strings (if that might help pinpoint you to something)

Tube Swap?

Jon
 
Re: Motorboating? (amp related of course)

Motorboating is an oscillation where the amp makes a noise all by itself. What you're describing sounds more like a ghost note - where a noise signal rides on top of the guitar note, modulates it, and makes it sound funny. In this case, the ghost note will stop as soon as the guitar goes silent.

In many cases, ghost notes are caused by 60Hz noise getting out of the power supply into the audio section. So, what you hear is the interaction of the guitar note and the 60-cycle signal. (OK, in Singapore it might be 50 Hz, but you get the idea.)

The most common cause of ghost notes is bad filter caps. Is this tube amp older than 10 years? If so, it probably needs its electrolytic caps changed. Certainly the power supply filter caps, and for good measure, any bypass caps on tube cathode-bias circuits.
 
Re: Motorboating? (amp related of course)

um
might this be anything like
how EVH in his solo sections bends his 22nd fret really high
and he gets this super high pitched whine
but not feedback
like
its weird
youd have to hear it
someone here will know what im talking about

that sound always bugged me
or..how he got it did anyway
haha
 
Re: Motorboating? (amp related of course)

I have an old Traynor that arrived to me with that symptom. It ended up being a bad solder connection to a ground wire. Clearly was jostled in shipping.....
 
Re: Motorboating? (amp related of course)

I had a distorton pedal "motorboat" after a cap value mod found on Harmony Central.

It would happen when the gain was turned up, and sounded like someone tapping out 16th-notes with their hands on an empty guitar case.
 
Re: Motorboating? (amp related of course)

Had that happen to an amp...turned out it was a pre amp tube.
 
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