Clean boost for guitar (or bass)

This is a transparent, clean guitar booster for solo’s and other times when you need a couple of extra dB’s. No ’boutique’ or other mojo-bullshit here, just a simple volume boost!

You can also use it to get some more gain out of an amp or distortion pedal. The circuit is a very common amplifier circuit built around a TL071-opamp. Other opamps can be used as well, but the TL071 is cheap and produces very little noise.

The ‘Boost’-knob controls the amount of boost, but can also attenuate the signal so you can use it as a sort of pre-settable volume knob.

Here’s the schematic:
Opamp Booster v1.0

Notes:

  • The maximum gain of this circuit is about 10 dB. If you need more (which I doubt), increase R2 (or decrease R1).  The gain A = 20*log(1+(R2/R1))
  • Rp is optional, it’s a pulldown-resistor to avoid ‘switch-popping’ when the effect is turned on.
  • The circuit also acts as a buffer since it has a high input impedance (about 1 MOhm). This will give you more overall ‘clarity’ (high frequencies) when you’re using long cables.
  • The booster is preferably used at the very end of the effect chain, just before the signal goes into the amp-input (or FX-return when using your amp’s effect loop).

Update: andre has provided a PCB layout for the booster:

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7 Responses to Clean boost for guitar (or bass)

  1. mike says:

    Thanks! I am going to build a bass boost for my fender using this schematic!

  2. erick says:

    i build this preamp with 14 db and have a brutal gain the best preamp

  3. Mark says:

    “If you keep R1 10k, and change R2 to 47k, the gain will be about 15 dB”

    Just re-read your post above:

    Do you mean keep R1 100K (not 10K) and change R2 to 47K?

    • Jeroen says:

      Sorry,
      R1 should stay 100k
      R2 should be changed to 470k

      So there were two errors in my previous post :)

      Then the gain will be 20*log(1+(470/100)) = 15,11 dB

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