I have an electric guitar with regular magnetic pickups and a Fishman Piezo bridge and preamp in it. The preamp splits the magnetic and piezo signals over each conductor of a TRS cable.
The problem I'm having is massive pop with any true bypass pedals. I suspected DC Offset might be the issue, so I put a meter to the guitar's output. From tip to sleeve I measured 3.7v DC, and from ring to sleeve I measured .05v DC. It measured negative with the red probe on the conductors and the black on the sleeve. I suspect it's because the 9v battery shares a ground with everything else, but I don't know much about any of this...
Isn't there a fairly simple way to build a pedal to remove all that DC offset? Could somebody make me a quick schematic? Or is it possible it's another issue entirely?
Thanks!
Put a sweaty finger on the "3.7VDC".
Does it drop way down?
Wait. Does it come back?
I am thinking your internal preamp has a leaky output cap. It is actually quite normal to have DC there right after switch-on. Sweaty finger (or 10K-1Meg resistor) will bleed that. But if it won't stay bled, the cap is leaking.
If you don't intend to fix the preamp itself, the box you're asking for is a cap in series with the T and a pulldow resistor across T and S at the output.
Quote from: PRR on February 07, 2017, 05:54:53 PM
Put a sweaty finger on the "3.7VDC".
Does it drop way down?
Wait. Does it come back?
I am thinking your internal preamp has a leaky output cap. It is actually quite normal to have DC there right after switch-on. Sweaty finger (or 10K-1Meg resistor) will bleed that. But if it won't stay bled, the cap is leaking.
great tip paul, thanks man...
i think you just solved an issue i was having with something else! ;)
DC removal box sounds like a $$$ scam for selling a gooped box with a cap inside. someone would probably buy it. they can't sue for false advertising.