Page 1 of 1
Preventing audio bleed in a stereo output
Posted: 16 Apr 2023, 22:16
by Ferniff
Quick question; got a bass with 2 pickups. Each pickup goes to it's own active pre-amp and then to it's own output (a 5 pin output (audio left, audio right, ground, V+, V-)). Pickup > Pre Amp> volume > output.
I'm having an issue where I'm hearing the bridge when I'm plugged into the jack that should just be the neck, or vice verse. What can I do to fix that? Would a big resistor by the input or output help?
Re: Preventing audio bleed in a stereo output
Posted: 16 Apr 2023, 22:44
by soulsonic
Does each preamp have it's own power filtering/decoupling? It might be the signals are getting mixed together via the power circuit. More filtering and decoupling can solve that if that's the cause.
Re: Preventing audio bleed in a stereo output
Posted: 16 Apr 2023, 23:09
by Ferniff
soulsonic wrote: ↑16 Apr 2023, 22:44
Does each preamp have it's own power filtering/decoupling? It might be the signals are getting mixed together via the power circuit. More filtering and decoupling can solve that if that's the cause.
No, they are sharing the same line for power
Re: Preventing audio bleed in a stereo output
Posted: 17 Apr 2023, 00:33
by soulsonic
If you insert a simple RC filter in series with the power going to each preamp, this could decouple the two channels from one another well enough to stop the problem. I would try a 150ohm resistor with 100uF electrolytic cap to ground. You'd split the line coming from the power and feed each channel in parallel, each with this filter in series. Since you said it has V+/V- bipolar power, you'd need four of these filters: two for the two V+ and two for the two V-. Does that make sense?
You may also need larger size electrolytic caps for the filters, but I've used 100uF many times and it has always worked without needing larger values - you can also increase the value of the resistor, but 150ohm should be enough.
Re: Preventing audio bleed in a stereo output
Posted: 17 Apr 2023, 20:55
by Ferniff
soulsonic wrote: ↑17 Apr 2023, 00:33
If you insert a simple RC filter in series with the power going to each preamp, this could decouple the two channels from one another well enough to stop the problem. I would try a 150ohm resistor with 100uF electrolytic cap to ground. You'd split the line coming from the power and feed each channel in parallel, each with this filter in series. Since you said it has V+/V- bipolar power, you'd need four of these filters: two for the two V+ and two for the two V-. Does that make sense?
You may also need larger size electrolytic caps for the filters, but I've used 100uF many times and it has always worked without needing larger values - you can also increase the value of the resistor, but 150ohm should be enough.
Thank you. I think I have a coupling capacitor at each power input, 100nf each. Here is the schematic I'm working with, it's a slimmed down version of the Alembic Super Filter
Here is the schematic:
I'm using a 5 pin cable/jack for Neck, Bridge, V+, V- and ground.
https://www.amazon.com/5-pin-din-connec ... +connector
Re: Preventing audio bleed in a stereo output
Posted: 17 Apr 2023, 21:59
by soulsonic
That imgur thing does not work for me. Please upload all images here as attachments.
Re: Preventing audio bleed in a stereo output
Posted: 18 Apr 2023, 01:05
by Ferniff
Re: Preventing audio bleed in a stereo output
Posted: 24 Apr 2023, 02:18
by soulsonic
Looks like what I suggested won't work, because you have both channels sharing the same ICs. Each channel would need to have its own for what I suggested.
And maybe sharing the same ICs amongst both channels is the cause of your problem in the first place.
