Need Help Understanding Something

[kd]

The amp is a 101 non-HRM. I recently added pre-amp out and power amp in jacks. The jacks not connected via a switch. You have to use a jumper to connect the jacks and make a circuit between them. Without the jumper there should be no feed the the phase inverter. When I remove the jumper I still have signal coming from the speakers. Can someone explain to me why I still have signal getting through? I thought with the jumper removed the amp would be silent.

Thanks,
Ken

[greiswig]

When you say "signal," what do you mean? You expect to at least hear some noise produced by the components in the PI and power section.

If you mean that you have signal into the input of the amp, and some of that seems to get to the output section in spite of no jumper, then I expect you've got some coupling somewhere in your lead dress or layout. But I'm not sure it's expected that you'll ever eliminate all of that. So the question might be do you have too much of it?

[kd]

I should have been more clear. When I say "signal", I'm talking about a guitar being played into the input of the amp.

Ken

[da Geezer]

You may need to post some picures of the effects loop jack area, or at least a schematic or drawing of what you did.........you may have wired the jacks incorrectly.

[Chris333]

Why not use a switching jack for the return, like the schematic? I can't think of an upside to leaving it out, off the top of my head... If you have the jacks (with switching jack in the return) wired like the schematic, you should have signal with nothing plugged in.

[kd]

.

[DonMoose]

Why not use a switching jack for the return, like the schematic? I can't think of an upside to leaving it out, off the top of my head... If you have the jacks (with switching jack in the return) wired like the schematic, you should have signal with nothing plugged in.

This is the thing - if you leave that input floating, it can pick up signal from a nearby low-impedance source, like a cathode lead. Plug a shorted dummy into the return, and I'd be very surprised if the crosstalk doesn't vanish.

[DonMoose]

Why not use a switching jack for the return, like the schematic? I can't think of an upside to leaving it out, off the top of my head... If you have the jacks (with switching jack in the return) wired like the schematic, you should have signal with nothing plugged in.

This is the thing - if you leave that input floating, it can pick up signal from a nearby low-impedance source, like a cathode lead. Plug a shorted dummy into the return, and I'd be very surprised if the crosstalk doesn't vanish.

[kd]

Thank you Don, you're a scholar and a gentleman. I removed all connections(no jacks hooked up and no connection between the master volume and the PI cap) between the PI and the pre-amp and was still getting sound. After reading your post, I grounded the PI input cap and no sound came from the guitar. You got it right, thanks again.

Since the cathode caps are next to the phase inverter input cap and bleeding over into the PI cap, how do I stop this cross talk which must be going on all the time?

Edit:
I just re-read your post, so with everything hooked back up correctly and nothing floating, the cross talk should be eliminated?

Thanks
Ken