I want to build a simple voltage follower to buffer headphones with the OPA1688. It will just be built on protoboard, considering how simple the circuit is I think it should still be possible to achieve close to the advertised ultra low distortion.

I will just follow basic, good design principles that you will find in nearly all op amp datasheets: Tying the output and inverting input pins directly together to keep feedback loop as small as possible. Adding ceramic bypass caps directly to the power pins. Adding individual ground wires from the power supply for audio inputs, audio outputs and bypass caps. I can not test how well it performs or even if the circuit will be stable, but surely following those steps there shouldn't be any problem?

  • \$\begingroup\$ Why can you not test how it performs? If it's an audio amp, can you not just feed it an audio signal and see what comes out the other end? \$\endgroup\$
    – Hearth
    Feb 25, 2021 at 4:33
  • \$\begingroup\$ Of course, but it wouldn't be a complete test. Ears would be reliable to test for significant distortion, the basic ADC in my PC would probably be able to test down to about -80dB but this op amp's performance should be approaching or even exceeding the limits of some professional analyser's. \$\endgroup\$
    – Jay
    Feb 25, 2021 at 4:42
  • \$\begingroup\$ If you're adventurous, build one with the 1688 and one with a TL072 or NE5532 and see if you can hear any difference. \$\endgroup\$
    – user156429
    Feb 25, 2021 at 7:22

1 Answer 1


Since you are talking OPA the layout given by Texas Instruments is something to treat as an holy scripture, especially with these high performance parts. Starting with a proto board is not exactly the best way.

As for distortion issue be careful on capacitors in the signal path, different technologies have different behaviour. In principle, films are better than ceramic in these circumstances (due to DC bias and piezo effects)

Most probably unless you have a $$$ audio analyzer you will not tell the difference.


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