Defining True Bypass and Buffered Bypass

Yesterday, I posted a review of the Boss TU-2 Tuner which I mentioned had buffered bypass. Eric commented and provided a fantastic link to a article by R.G. Keen which works at Visual Sound Pedals. My post about Visual Sound’s Route 808 pedal is what started my tangent / interest in buffered bypass.

Here is a great explanation of the differences between True Bypass and Buffered Bypass:

Once guitarists noticed that their CLEAN sound suffered from having a bypassed effect in the line, they demanded better bypasses. This came in two flavors, true bypass and buffered bypass.

Buffered bypass is the technique of designing a high input impedance amplifier to go ahead of the actual effect circuitry. The input impedance of this buffer is high enough to avoid tone sucking, and it has an output impedance low enough to drive the rest of the effect with no loading even if the effect proper has a low input impedance. This also allowed electronic switching from dry to effected signals, and became a favorite of several Japanese electronic companies. The best example is probably the Ibanez xx-9 series, which includes the fabled Tube Screamer 808 and 9. These effects do not get a lot of reports of tone sucking, although purists sometimes demand that they be converted to true bypass.

True bypass is the standard of clean signal quality against which all other bypasses are measured. True bypass means that when the bypass switch is in the bypass position, the effect circuit is entirely disconnected, input and output, from the guitar’s signal, and that the signal passes from the effect input to its output going only through wire and switch contacts. To see how a true bypass works, we can make up a hypothetical set of single pole, single throw (also know as simple make/break) switches and concoct a true bypass. For this, we only need three simple switches and some timing. Clearly we need two switches to break the path from the input jack to the effect input and from the effect output to the output jack. If these two are simultaneously opened or closed, they connect or disconnect the effect from the jacks.

I’m going to do some personal experiments with true bypassing and adding a buffered item in line. I’ve been so use to my tone, that I need to shake things up a bit and see I hear a difference with my current set up. Or at the very least, if I can replicate a complete true-bypass signal path to see if things darken.