The Truest Bypass
The Vertex Dual Buffer sports separate input and output buffer circuits, each designed for its specific task. Photo courtesy of Vertex Effects
What could be better than having “true” bypass in your pedal? This sounds like an indisputably good idea, but in fact, it’s not that simple. The subject has been written about before, but there is such confusion regarding true bypass that it’s helpful to revisit it from time to time. When it comes to preserving optimum tone, how you bypass and wire your pedals can be as important as how you power your pedal. (For more on this topic, see “Powering Your Board” in the December 2011 issue.) Let’s take a look at how both true bypass and buffered bypass work.
The idea of true bypass is that when your pedal or effect is off, there are no electronic components whatsoever touching— and thereby having an influence on—your guitar signal. This sounds great in theory, but there are some practical problems with the approach. In almost all cases, guitar pickups are passive, high-impedance devices with a relatively wimpy ability to drive a signal. Think of it as a trickling stream of water rather than a pressurized pipe. It’s very easy to divert a trickling stream with a few small rocks, but not so easy to place those rocks in a high pressure pipe without them simply being blown out.
Because the signal coming out of a guitar is weak and easily influenced, even the wire in your cables and true-bypass circuits can degrade your tone. The degradation you may hear will manifest itself as a loss of high frequencies—or “tone suck,” as many refer to it. This is caused when a simple low-pass (treble cut) filter is created with a passive RC circuit. The “R”, or resistor, is the combined resistance of all the cabling in your rig. The “C”, or capacitor, is the inherent capacitance present in shielded cables. Each true-bypass circuit adds unbuffered cable length—and therefore more resistance and capacitance to the signal path—so they create an unintentional low-pass filter.
Another problem is that the 3PDT footswitches commonly used in true-bypass circuits are not optimized to switch low-voltage signals like guitar pickups. The side effect of this can be noise or pops when switching in and out of bypass. The physical distance between the input and output jacks and the switch can also exacerbate this switching noise, in addition to adding internal cable length. A better way to accomplish true bypass is to use a relay that’s optimized for switching small signals. Such relays can be quieter and placed in an optimum location in the pedal that minimizes cable length when the pedal is bypassed.
The other way that pedal manufacturers implement bypass circuits is, of course, with solid-state electronics. This is often done with FET switching circuits and is called buffered bypass or analog bypass. A simple truth that escapes many is that any pedal with active electronics in it automatically and by its very nature will include a buffer.
Now, the quality of that buffer can vary greatly from manufacturer to manufacturer, but when buffered bypass is done well, it can be a very good method of bypassing a pedal. It provides a robust and relatively silent form of switching. Buffered bypass has simply gotten a bad name over the years because of poorly designed buffered bypass circuits that color your tone.
Because of this, and for fear of any extraneous electronics hanging on to their guitar signals when bypassed, many players insist on only using pedals with true bypass. Players who use batteries in their pedals also have to worry that once the battery dies, not even the dry-bypass signal will pass through the pedal because it requires power to do so. One drawback of buffered-bypass circuits is that pedals not using low-noise components and designs can add a significant amount of white noise to the signal chain even when the pedal is bypassed. This can usually be minimized with a correctly designed bypass circuit.
So, what’s a pedal junkie to do? There is, in fact, a best-of-both-worlds solution: Place a good quality buffer at the beginning of your pedalboard signal chain. This can be in the form of a compact dedicated buffer, a clean boost set to unity gain, or even a pedal with a high-quality integrated buffer that you don’t mind leaving on all the time.
In my personal rig, I leave an optical compressor set to a very light compression level on all the time, and it serves as my up-front buffer. What the buffer does is transform the trickling stream that is your guitar signal into a pressurized fire hose of a low-impedance signal. This significantly minimizes any degradation that can be caused by having many true-bypass pedals or lots of cable in your rig.
Having a buffer up front becomes extremely important when using a true-bypass “looper,” a device that bypasses effects externally with multiple true-bypass effects loops. In practice, those devices add a ton of extra cable to your rig. Again, a buffer up front will minimize any harm they can potentially do and let you take full advantage of true bypass. In short, put a buffer first in the chain, trust your ears, and rid yourself of bypass anxiety. Happy shredding!
Terry Burton is an engineer at—and the founder of—Strymon.