This is one of the simplest OpAmp circuit which can be used as a clean volume booster or as an preamp into your speakers. With this simple circuit you can turn your any speaker system into a guitar practice amp. I first created it in separate box and then I directly installed in speaker itself using mini monojack socket so it can serve me as pedal too :)

This is a transparent, clean guitar booster for solo’s and other times when you need a couple of extra dB’s.

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.


• 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. (I used it in my circuit)

• 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).

(I got details from this link http://www.jer00n.nl/2010/07/28/clean-boost-for-guitar-or-bass/)
<p>There's one problem with the design: too high input signal will clip the op-amp's output, and you get dirty boost. Any signal past 1.4V (with ideal design, probably closer to 1V) will cause clipping to appear. Setting the potentiometer in the feedback loop (replacing the 220k with a 100k resistor in-seires with a 100k potentiometer) will let you control the amount of boost and avoid clipping on the way.</p>
Hi dude..!! this circuit works with LM386 too so please mention the name in the alternative OP-Amp because TL071 is sometime hard to find for others. Have a wonderful day

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Bio: Hi, I'm actually an IT consultant but love engineering. I love to try, do DIY stuff which are cost effective and solve my purposes.
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