Ghost notes in an Ampeg Reverberocket

[rollo greb]

I have an Ampeg Reverberocket GS-12R that has a problem with ghost bass notes, especially when I play high up on the neck or do double stops. Now I know a lot of amps do this, but this one is getting so bad that I can't even use it anymore. Which is a shame because apart from this problem the tone is great.

I just replaced the filter caps hoping that might solve the problem, but with no success (though it did reduce the hum). Has anyone had this problem with an Ampeg, or any other amp for that matter?

[akimball442]

I wish I could provide an answer to this... instead I have to ask the same question... What causes this? One of my more recent builds had the same problem. It's very strange. I think they are some kind of harmonics or something, particularly noticeable at higher gain settings.

[Snapcase]

Are any of the original electrolytic caps original? When electrolytic caps start to go bad (very likely in any 40 years old amp) ghost notes and subharmonics plus other odd issues are nothing strange. I mean all of them, not only the PSU rail filter caps; cathode bypass caps, Bias rail caps...

[pdf64]

I assume this used to be ok and has got worse?
Three possibilities I can think of-
1. a bad tube - output tube most likely.
2. a replacement cap is bad - just tack a known good one across each in turn.
3. there's a bad ground connection - if grounded to chassis at transformer fixing, maybe nut gone loose, or oxide on chassis building up.

[tubessence]

Check for a loose tube socket, seems to be a problem on these. jb