Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Rosewood, Sep 23, 2008.
Other than bad filters or under filtered what would be some more causes of ghost notes?
I've got a super reverb with new filters and 6l6's within 3 ma. and all coupling caps in good condition so I'm stumped on this one.
A 'hot' bias setting will ghost note too.Very old guitar strings will ghost note sometimes as well.
Some people like to bias their super's very hot,over 40ma.I find some tubes don't like it at all.
They are biased a little hot, these are JJ'S and I've never had a problem at 60 -70%.
It's not cone cry, I've heard enough cone cry to last me a life time. I will try another set of tubes and maybe a different bias point. BTW the output trans seems to be balanced ok.
My guess would be speaker cone cry or other speaker related noise. Fairly easy to check out, unplug the built-in speakers and plug the amp into an external cab and see if the noise/ghost notes persist.
As long as you don't play too long or too loud to test this you don't need to worry too much about speaker cab impedance mismatch, but if you can come close (e.g. 4 ohms for the external cab) that would be better.
Easy to check out and can certainly cause the effect you're describing.
I gotta ask the obvious, but how are your pickup heights? Too close to the strings and you'll get ghost notes.
As others have mentioned there are a number of things that can cause ghost notes.
If youve already eliminated the obvious and are really stuck then you might want to look at the screen grid resistors on the power tubes.
It has been my experience that even though they may read "good" on a meter and they may even "look" good.... but if you go ahead and swap them out you will get rid of that annoying 2nd note.
Tried different speakers but no improvement. The point about the screen resistors is interesting, they both measure about 467 ohms but they are wirewounds, I wonder if film or carbon would be better. I've always used wirewound screens and never had a ghost note problem. Tonight I checked the layout of the wiring to see if someone had rerouted something in a way to cause a problem but everything looks normal. Tried several guitars, all setup well, not a pickup problem. Could it be the Devil trying to tell me something? This a strange one. I may try another rectifier tube simply because I'm out of ideas.