OC-2 ghost effect on guitar but not bass
Weird problem I discovered a couple days ago...
When I use my Taiwanese OC-2 with a bass, it works perfectly. When I use it with guitar, I can hear it faintly putting out a lower octave when I have it switched off. Quite disconcerting. I'm at a loss to figure this one out. Why would it only do it with guitar? Has anyone else ever had this problem with the OC-2? If so, what was causing it?
Maybe it's doing the same with the bass, but it's so low in frequencies, or your bass masks it so that you don't hear it?
Same amp, different amp?
I can try to reproduce it with my Oc-2 later today
The signal path was OC-2 > TAFM > Tech 21 British > REDDI > Fast Track > headphones for both. Not tried it in an amp yet. But I thought about it being too low to hear and tried the bass' high notes...doesn't do it on them, either.
I did the synth mod to a mit oc2 and found the ghost notes on bass as well. The solution was to move the wires on the inside so they weren't so close together. I don't know about a stock pedal though, but it might have given you an idea
Is there a large difference between the output impedances of the bass and guitar that
you were were using? A lower impedance instrument could be more immune to signal
bleed through from the sub-octave generator circuit (which is obviously always active).
A higher impedance is more susceptible to noise or extraneous signal pickup.
A passive P bass circuit would be most sensitive at a volume setting of -6db (5 on a
linear pot, about 8 or 9 on an audio taper). A passive J type circuit would be most
susceptible at low volume settings.
Same is true for guitar depending on how the output impedance changes with volume
If the instrument has a preamp, the output impedance would remain low regardless of
the volume setting, and would be more immune to any extraneous signal pickup.
Don't know impedance difference, but they were both passive.
Going to try the wire thing since it's easy ;) My OC-2's at my gig, though, so it'll be tomorrow before I can report back. Thanks, folks!
Jimmy, I think the problem that you are having is if you are daisy-chaining the Tech21 power with your other pedals. Here is some information from another thread:
I just found an old Boss schematic for an OC-2 that shows a diode and 470 ohm resistor in the ground from the power jack. If the schematic is the same for your OC-2 then you have another pedal that will cause a ground loop when daisy-chained powered with other pedals.
The ground loops are even more complex because there are at least two pedals now sending their return power currents through the patch cables, through the other pedals.
Maybe you can try a battery with the OC-2 also.
Ah, that would make sense. Was powering everything with a single 1-spot. Weird how it only did it with guitar, but maybe there's something weird about the guitar that needs addressed. Thanks, Frank!
There is probably nothing weird about the guitar… ground loops just do crazy things. Sometimes, even if you don’t change anything at all, they can cause issues that seem to come and go.
Please let us know what you find.
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