Simple buffer and phase inverter

10/16/2017

Here is a small utility board - a simple buffer followed by a phase inverter. You can take the output from either stage. It can be very useful if you are adding a clean blend to a circuit that is inverting the phase.

I recommend putting this in front of your main effect, but keep in mind that not all effects will respond the same with a buffer in front. I didn't include polarity protection, DC filtering and an output capacitor since this is meant to be used together with another effect (not stand alone).

12 Comments

Michael

2/12/2018 05:14:53 pm

Hi, I built this and it seem to work just fine. It took me two hours of troubleshooting until I read your last remarks though :) Is it possible to use this at the end of a pedal chain before a last splitter? And what value cap would you choose for the output cap?

Fredrik Lyxzén link

2/13/2018 01:40:58 am

Hi Michael,
Yes, you can put it at the end of a pedal chain. Capacitor value isn't critical (anything from 100nF upwards will be fine) unless you will put a volume pot directly after the output cap, then the cap + pot will act as a highpass filter when turning down the volume. In that case, use a large value, like a 2.2uF electrolytic cap (the negative leg going to the pot) to avoid too much lowend being cut.

Michael

2/13/2018 09:07:28 am

That was exactly what I wondered, thanks a lot!

Sebastian

7/27/2018 07:31:01 am

Hallo Michael,
i would use your circuit for my Fulltone Tube Tape Echo. There is a 440 ohm output impedance. That’s why I need a buffer. It is possible to use your circuit for that and could I operate it with 12v?
Cheers, Sebastian.

Fredrik Lyxzén link

9/27/2018 07:05:56 am

Yes, it should work fine with 12v. Just remember to add an output capacitor (any value 100nf - 10uF will work. Negative side to the output).

Marcus

2/8/2019 08:39:45 am

Hello. Thank you for this layout. Very good to find this. I have one more question. Is it possible to use your layout as dual invert buffer? because i have a stereo effect with two outputs, bouth out of phase with around 200k output impedance. Thats why i'm looking for a dual buffer with invert.
Would be great to hear from you.
Best Regards, Marcus.

Fredrik Lyxzén link

2/8/2019 11:45:32 am

Hi Marcus,
You need two of this layout to use it as a stereo buffer. One input buffer and one inverting stage for each channel.

Cheers / Fredrik

Marcus

2/19/2019 12:34:34 am

I did it. But the signal is clipping. Is it normally with this circuit?

Fredrik Lyxzén link

2/19/2019 01:03:41 am

It should not be clipping unless you have a very hot signal. In that case you need to attenuate the signal before the input with a voltage divider, or run the buffer/inverter at a higher voltage (18v)

krabasti

2/10/2019 12:52:28 pm

Hello Fredrik, thanks for your quick reply. i just built this Buffer and really like it, but I've noticed a really odd issue that I can't figure out. When I plug my Guitar and turn up the volume knob i get noticeable noise. If I turn down the volume the noise goes away. I've tried power supply as well as battery with the same results. What can i do?

Marcel

10/7/2019 03:14:36 am

Is it possible to use this buffer (tl072) with 10 Mohm resistor for higher input impedance?

Marcel

10/8/2019 01:55:37 pm

or maybe with 3 Mohm. which resistors i have to change, R1 and R2?

Simple buffer and phase inverter

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