Super Buffer for Guitars

Posted on Feb 5, 2014

There are situations in which very long cable runs are necessary from the pedalboard to the amplifier, or a more powerful driving circuit is needed to the heavy load presented by devices in parallel. A good buffer box is the solution. The best buffer board will present a high impedance to the input while having a low impedance output. This insures

Super Buffer for Guitars
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that the maximum clear signal will pass through unchanged to the output, and a low impedance drive can send the signal through long cables without losing much strength or response. There are numerous special purpose chips that are designed as buffers for driving very long lines and/or capacitance loads. These ICs can be difficult to find and expensive. A simple solution for stompbox purposes is to parallel opamps and thereby boost the output drive. With attention to a few details, this is a simple project to build. The circuit has four opamps placed in parallel. The outputs are isolated by resistors R1 through R4 which make sure the opamps share the output drive and no single one is carrying the bulk of the load. Resistor R5 is an pop prevention component and can be eliminated if desired. The value of R6 is essentially the input impedance if R5 is not used. When R5 is included, the input impedance is the parallel value of R5 and R6. Two capacitors are used on the output - since we do not know what load this circuit may be driving and we want to get full response, a 10uF output capacitor (C3) is a good value to chose. A 0. 1uF metal film (C2) is placed in parallel with C3 to insure that the response remains flat at high frequencies where the rising impedance of electrolytics could effect the sound. C2 could be left out without sacrificing much. An additional tweak is to make the R6 resistor a metal film component for lower...

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