Really, no need for any buffer?It will work straight into the audio shield, if you just want mess around with it - like Pio's stereo guitar emulator. It might have to some high end roll off, though.
Thanks very much for that great info. I won't be using the usb port for power. This schematic is a preliminary design, but yes a bypass switch and a negative center power adapter plug is the electric guitar way to go. Appreciate the help, thank you.@TonyAme, be aware that you can't connect 5volts from USB at the same time as 5V from regulator. They will fight each other. there are multiple solutions to this issue.
You could add a jumper plug/pins to the 5V regulator output. Remove jumper when using USB to program Teensy. However, this is prone to forgetting to remove the jumper.
You could add 2 diodes to form a diode OR'ing circuit. 1 diode is at the output of 5V regulator. The other diode is placed on bottom of Teensy as shown at PJRC page: Using External Power and USB (shown for a different Teensy family, but same procedure). Don't cut the pcb track too deep or else you could penetrate into the inner pcb layer copper. Go slow and check with multi-meter that the track is cut. The diode OR'ing is pretty foolproof in usage.
You can cut the USB cable 5V wire. Just don't mix up your USB cables and plug in a cable that isn't cut. Prone to mistakes.
We can't see your entire schematic, but I would suggest you add a Bypass switch to the design.
BTW, most guitar pedals (but not all) use a -ve center pin for power adaptors. Make sure whatever adaptor you are using matches your +ve center pin design.
Good luck with your project. Let us know how it all worked out.
Thank you. Will check out your stereo buffer, appreciate it.A guitar with active pickups will have the buffer is already built in. Otherwise, i'd recommend a HiZ buffer.
Plenty projects are available online. I've made a simple stereo buffer project which can be soldered on a perf board:
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TGX4/diy_buffer.md at main · hexeguitar/TGX4
Tennsy4 based guitar amp emulator. Contribute to hexeguitar/TGX4 development by creating an account on GitHub.github.com
Since your output is mono, you could use one buffer channel for the input and the second after the OutputVolume pot. This way the pedal will have proper instrument HiZ input and a constant low impedance output.
Filter connection is correct. OUTGND, LINGND, RINGND are the same signal. The only "different" ground is the one used for headphone output.
I'll be removing the Teensy + audio board from the circuit whenever I program the Teensy. Is there something I'm not seeing in my schematic concerning the 5V input from the 7805 regulator? (I do often not notice obvious things when constantly looking at the same schematic for a long time.) Please let me know if that's happening here...lolSo..., how do you intend to program Teensy?
Turning switch SW1 OFF is not a solution. Regulators don't like seeing 5V applied to their output pin.
You should isolate the regulator 5V output from the USB 5V source.
No as you don't have a coupling capacitor in the audio signal path. The resistor would discharge such a capacitor when the input is disconnected.Would using a 1M resistor here be useful for an anti-popping solution caused by a mechanical toggle switch?