Update (10.07.2014): Minor changes to the schematic and vero layout to make it work properly with the tap-tempo clock project; tap input switch, series resistor and sync input.


Update (01.06.2014): Having built this it didn’t sound as good as what I was aiming for (the Phase 90). After a lot of debugging I found that, unlike the 90, I was missing a 2x gain stage at the end. Two resistors later and it now sounds great!

Revised schematic, and the vero layout has been updated accordingly. Now it only needs an enclosure 🙂


Merry christmas! Here’s an early present from me 🙂

This is a tap-tempo adaptation of the MXR Phase 90. It’s pretty much identical except the LFO has been replaced with the tap-tempo chip (v2), and the remaining opamp was used in place of the transistor output buffer.


The multiplier should definitely be included, but the waveform isn’t necessarily something that needs to be changed (I only liked the sine- and triangle waveforms) so this could be an internal trimpot. The multiplier can be either a regular pot or a 5T rotary (see the tap-tempo tremolo on how to do this).

Vero layout to come soon…

Update (23.12.2013): First schematic revision. That bias trimpot should definitely be 500k, not 10k.

Update (26.12.2013): Vero layout based on the schematic above.


I chose to use an internal trim pot for the waveform selection. I felt only the sine- and triangle waves was any good, and they sounded very similar. R21 is omitted because I had trouble making room for it, and it’s not strictly necessary.

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5 thoughts on “Tap-tempo Phaser

  1. Hi Patrick,
    I read that you created a separate board for the tap time for phase 90. I have a phase 90, you can sell a board configured to me and you write to me the instructions to install him?

  2. Hi Harald,

    this was very helpfull to me in order to add the Tap-tempo to a previuously realized MXR Phase 90 clone. Just realized a vero board for the Tap-Tempo section and connnect it the way you specified to get the complete Tap-tempo Phaser.

    Thanks a lot.


  3. Happy Christmas to you too, this indeed is a nice present, I was planning something similar, now I don’t need to think how to adapt your tap-tempo solution to the Phase 90 🙂 Thanks a lot!

  4. Merry Christmas to you, Harald! Thanks for the site. And a happy new year to you as well…

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