1
\$\begingroup\$

So I'm trying to build a guitar amp switcher (and I don't really know what I'm doing =)).

The idea is that guitar out is connected to X4 jack and then switched to either X1, X2 or X3 jack, which goes into amps input.

Then amps speaker out are connected to X5, X6 and X7 jacks and selected output is routed to X8 jack.

S1, S2 and S3 switches are parts of 4 pole 12 way rotary switch.

Currently, I tried a schematic listed below:

Current schematic However there is a high pitched noise when using it which disappears when I use some kind of guitar pedal before guitar in.

If I connect everything this way I get high pitched noise (everything is connected with TS cables): Noisy

And this way there is no noise: No noise

Is there any way to fix this issue?

\$\endgroup\$
  • \$\begingroup\$ Have you tried two X8 options? The ring of the headphone jack tends to be the ground and the tip the signal. On the X4 setup, you have tied all the signals together and are switching between the grounds. \$\endgroup\$ – vini_i Feb 25 at 0:24
  • \$\begingroup\$ @TylerStone Guitars tend to use 1/4 in headphone jacks and the schematic shows headphone jack symbols. I read between the lines. \$\endgroup\$ – vini_i Feb 25 at 0:45
  • \$\begingroup\$ @vini_i fixed it, thanks. It is only a misprint in a schematic -- I route jack tips in a real device. \$\endgroup\$ – Yakkodash Feb 25 at 1:13
  • \$\begingroup\$ DC supplies leak a lot of common mode noise on unbalanced cables and the "guitar pedal:" may have a Balun or INA balanced Op Amp in it. Show a block diagram of all the supplies and earth ground. \$\endgroup\$ – Sunnyskyguy EE75 Feb 25 at 1:37
  • 1
    \$\begingroup\$ The Guitar Pedal buffers and lowers the guitar signal impedance and I suspect there is positive feedback at the high pitched frequency from crosstalk. Can you link the DPDT "switch"? \$\endgroup\$ – Sunnyskyguy EE75 Feb 27 at 20:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.