Quadruple Bypass : The Four Most Common Bypass Types, Impedances, Buffers, and You
Lane Sparber
True Bypass. IS IT TRUE BYPASS?!?!
That's usually the first question most musicians I've dealt with ask about any pedal because that's clearly best, right??? Is it true bypass? Can it be modded to be true bypass? If it's not true bypass, is it even worth purchasing? Okay, that last one's a stretch, but I've had clients who ALMOST drew the line there. So, ALL pedals should be true bypass, right?
Well, not so fast. There are many applications where a pedalboard with ALL true bypass pedals will actually sap and hinder your tone. Why? How? Please read on, and I'll explain it as best I can in the simplest ways possible. My intention is to help musicians like yourself gain a better understanding of what's going on at your feet (literally) - even if you happen to have NO prior electronics training or background. So let's dive right in!
THE FOUR MAIN BYPASS TYPES
Mechanical true bypass:
This is the most common type of true bypass. It's cheap and easy to implement. The stomp switch itself physically controls everything. Being true bypass, the input is DIRECTLY hard wired to the output when the effect is off. This method has the advantage that the pedal will still pass signal in bypass even if the power to the pedal itself goes out.
Electronically controlled true bypass:
In these pedal designs, relays or JFET transistors (both are electrically controlled switching devices) are used to implement the switching. The main advantage to this type of circuit is that it's usually dead silent (no popping or clicking sounds when actuated), and it's instantaneous. The disadvantage is that if you lose power to the pedal, your signal will die whether it's in bypass mode or not.
Split "true" bypass:
In my opinion, this is the least desirable type of bypass, and thankfully it's almost exclusively found in older vintage pedals. In the early days of effects pedals, the most commonly available (and reasonably priced) stomp switches were single-pull/single throw. These switches had ONE output that could be connected to one of TWO inputs. In the most common scenario, this meant the stomp switch just switched the pedal's output jack between the affected signal from the pedal and a signal straight from the input jack. The problem is that this design necessitated that the signal from the pedal's input be SPLIT between the effect and bypass paths. This design was far less than ideal because even in bypass mode, some of your signal is STILL being sent to the effect itself. Splitting a high impedance signal that way will always cause some loss of tone - particularity in the high frequencies. By way of example, most vintage MXR pedals used this topology, and if I get one in the shop, I'll usually mod it with a modern DOUBLE pull, DOUBLE throw footswitch to make it genuinely true bypass if it's going to be used at gigs. I'll explain more about these switch types in a bit.
Buffered bypass:
In these designs, the pedal's input goes into an electronic buffer, and the output of that buffer is sent to the output jack when in bypass. I'll discuss buffers and why they're used below, but suffice it to say for now that these pedals are extremely common. For the record, almost all BOSS compact pedals use buffered bypass.
COMMON TYPES OF STOMP SWITCHES AND HOW THEY WORK
Single Pull / Double Throw ("SPDT"):
These are the most common types of footswitches in vintage pedals. As stated above, an SPDT switch has one single terminal that can be connected to EITHER of two output terminals. Thus, only the input OR output signals can be switched in pedals with an SPDT switch.
Double Pull / Double Throw ("DPDT"):
The most common switch type in modern true bypass pedals is the DPDT. Simply put, they are TWO completely independent SPDT switches in one. These nifty switches can control the input AND output paths of the pedal at the same time, allowing the input to be directly connected to the output in bypass mode.
Momentary:
Momentary switches simply make contact "momentarily" between two (or more) terminals when activated. When you release the pedal, the connection breaks again. These are used most commonly in sophisticated electronic switching arrays such as the "flip-flop" bypass circuits in BOSS pedals. They're a bit beyond the scope of this article. However, I feel it's important that all of you know what's out there.
IMPEDANCES … AND HOW THEY AFFECT YOUR SIGNAL
There are two basic types of electrical signals when discussing audio gear: high impedance and low impedance. Now, I'm going to (almost criminally) over-simplify here to give a basic understanding of what both of these are and how they apply to your rigs.
All passive guitars and basses will send out a high impedance signal. In general, high impedance signals have more voltage (size of signal) and less current (force of signal). Because they're inherently weak, they're susceptible to almost any outside force that acts upon them. In particular, their high frequencies are especially delicate, and this is why your instrument can sound dull and lifeless when you run it through a 25-foot cable. These signals are also extremely sensitive to any outside electronic "noise," such as RF interference and even local radio stations! Thus, if you're using a LOT of effects (or playing 100 feet away from your amp), you've really gotta be careful about how many devices and the cable length to which you subject a high impedance signal.
On the opposite end of the spectrum, we have low impedance signals. A low impedance signal GENERALLY has low voltage (amplitude) levels but much more current (force) behind it. These types of signals are FAR more robust than high impedance signals, and they're all but impervious to factors such as long cable runs and RF/radio interference. They're pretty strong little buggers!!!
BUFF-OONERY : WHAT'S A BUFFER???
Simply put, an electronic buffer in a pedal takes an input signal and makes a copy of it. This copy is then sent to the rest of the pedal and the output jack when in bypass mode. A buffer does NOT actually amplify the signal; that's not its job. In effects pedals they're most often used to convert your instrument's HIGH IMPEDANCE signal to a LOW IMPEDANCE signal. As you've already learned, high impedance signals are very delicate and are easily weakened and degraded. The buffer thus protects your instrument's delicate signal from being "weighed down" by the rest of the circuit. Ideally, they will also maintain the integrity of your tone in the process. That said, not ALL buffer designs were created equal - particularly in vintage pedals when the technology was new. That's in part how the bad reputation surrounding buffered pedals got started, in my humble opinion.
SO WHAT DOES IT ALL MEAN???
Should you ONLY have true-bypass pedals in your rig? Well, that depends. Keep in mind that any true bypass pedal will run your delicate high impedance signal through anywhere from about 4 inches to over a foot of extra wire when in bypass mode, and this adds up quickly. In a worst-case scenario, If you have 10 pedals on your board, that's like running through an additional 10-foot cable! That can really dull your high end, and I wouldn't recommend it. I think the best solution for a larger rig is to use at least ONE buffered bypass pedal at the front end (just after the guitar). A BOSS tuner is an excellent choice. In reality, you only need one because once your signal is converted to low impedance by a buffer, EVERYTHING downstream from it will automatically be low impedance regardless of what types of pedals you have. Once it's converted, it's permanent. Some REALLY cool pedals have a switchable internal buffer that you can activate or deactivate based on your needs, which I think is fantastic.
Conversely, If you only use two 10-foot cables and three pedals, then all of your pedals being true bypass won't affect your tone much when turned off, so I'd say go for it.
THE END OF THE LINE
As you can see, the correct type of bypass for you depends on your rig. Sometimes having all true bypass pedals is ideal, and sometimes it can seriously degrade your tone. You have to make informed decisions about what's going on with your board. When in doubt about a particular pedal, the manual or online literature will usually tell you how your bypassed signal is handled. If you're concerned, you can purchase a looping switcher that will automatically take the pedal(s) fully offline when bypassed.
I know all of this can seem daunting, but a basic understanding of how signals work is essential to executing an informed and effective pedal board design. I hope this humble article helps you achieve the pedalboard of your dreams, true bypass or not!
Lane Sparber is an amp / guitar / bass / pedal tech who lives and works in Fresh Meadows, Queens, New York. He started repairing gear in his mid-teens, and he’s 46 now, so you do the math. When not causing mayhem in his workshop, he can be found desperately trying to hide his latest orchid purchases from the rest of his family. You can find him on Instagram at @amptech74 or on Facebook at www.facebook.com/lane.sparber. Come say “Hello!”
