Poor output drive capability, or to put it another way too high output impedance, is also a problem with certain effect pedals too. Even when the pedal is engaged the buffer circuitry may not be able to adequately drive the load that cables or other pedals present. A buffer can be used after these types of pedals to prevent tone loss.
Now, this brings us round to that perennial debate guitarists and sound engineers forever keep coming back to—buffered verses true bypass pedals: which is best? Well, the short answer is neither. Both approaches are compromises in one way or another. A buffer stage will always affect tone. Even a well designed buffer made with top grade components, such as the Effectrode ‘Glass-A‘ will introduce a small amount of noise or hiss into the signal—it’s physics (Johnson–Nyquist noise in engineer-speak), every amplifier does, and a buffer is technically a unity gain amplifier. You may not be able to hear it with just one pedal, however noise becomes increasingly apparent as more pedals are added to the signal chain as shown below.
And a well designed buffer is the best-case scenario. In reality there are many effects pedals out there with below par buffers that are not only excessively noisy, but introduce unwelcome artefacts and unpleasant sounding distortions, such as crossover distortion and slew-induced distortion, and also curtail the bottom and upper frequency response causing loss of oomph and sparkle, in short, “tone suck”.
But true bypass effects also have their shortcomings. The disadvantage here is one of accumulated contact resistance and capacitance of the footswitches and jack connections when many pedals are connected in series. As more pedals are added to the chain the tone becomes duller as the capacitance of all those footswitch contacts in parallel adds up.
But there is a simple fix for this: place one buffer at the beginning of the chain. This way you’re getting all the advantages of true bypass (no added noise and distortion) and none of its disadvantages (tone loss due to accumulated parallel capacitance and resistance). A single buffer at the beginning of the chain is the optimum engineering solution for best possible guitar tone.
One final scenario where a buffer is useful is with certain effects that are prone to self-oscillation. These include some wahs, fuzzes and the Effectrode ‘Phaseomatic’ tube phaser. If these pedals see a high input impedance or open circuit they begin to ‘chirp’ or squeal uncontrollably generating sounds independently of the guitar input signal. In some cases this might be desirable, for instance if you’re trying to create 1950s sci-fi effects with the Phaseomatic, however if you’re in a live situation you, your audience and especially your sound engineer won’t appreciate hearing a wah-wah pedal squealing uncontrollably. Placing a buffer before these problem pedals will ensure they always see a low impedance and prevent self-oscillation.
So, in summary, use a buffer in the following situations:
- To drive long guitar cables.
- To prevent loading caused by older effects pedals with low input impedance.
- As a first buffer stage to drive a chain of true bypass pedals.