What is a True Bypass Guitar Pedal - Why do I Care?
Have you ever heard the term true bypass and wondered exactly why you would want that for your guitar pedals? Is it a lot of hype or is it something that you might want in a pedal? Ill try to answer that for you.
Quick Summary: I think a true bypass guitar pedal is better because you get more control of your pedals. Here is an in detail article talking about the pros and cons.
For true bypass, we are basically concerned with what happens to your guitar tone when you have a pedal plugged in, but in the OFF position. For some guitar pedals, such as many Boss pedals, a circuit is always plugged in even when you dont have the pedal in the ON position. This means that even when you have the pedal off, it is still doing something to your tone and you have no control of this unless you mod the pedal. For people that want total control over their pedals, then true bypass is the answer.
Figure 1. True bypass means that when the guitar pedal effect is OFF, the effect circuit is not connected to anything (top left). The green signal shows that your signal goes in and then comes out. On the right, it shows what happens when you turn the effect on, your green signal goes through a circuit which makes the effect. There is nothing connected when the pedal is off and nothing sucks away your tone.
The basic idea of true bypass is really simple; a true bypass circuit allows you to completely remove the guitar effect pedal from the guitar signal when the pedal is OFF. Figure 1 shows a picture of what a true bypass circuit looks like compared to a pedal without true bypass shown in Figure 2. The green arrow shows how your guitar signal travels through the pedal.
Figure 2. Pedals without true bypass can have the input to the effect circuit always connected which sometimes results in tone sucking even when the pedal is off. Following your green guitar signal in the left picture, when the pedal is off, a switch chooses to send the signal directly to the output. However, note that your signal is still connected to the input of the circuit, which can have a low enough impedance that it takes away some of your tone (tone sucking). On the right, when the pedal is on, your signal goes through the effect.
The big difference is that a guitar signal going into a pedal without true bypass still sees some of the effect circuit even when the pedal is OFF. Notice that the green arrow goes both to the output and to the input of the pedal circuit (bottom left picture). It could be stray capacitance, the input resistance of a biased transistor or a dedicated buffer circuit. When it does have true bypass, the signal goes into the pedal, through the switch and back out of the pedal with no additional circuitry connected to the guitar signal path (top left figure).
Why would I want true bypass
There are a couple reasons to want true bypass, but mainly that you dont want any portion of the effects on your pedal board to change your tone. This is the kind of stuff for people that want to control everything. . . This is so that no circuit portion of one pedal interacts with any other circuit portion of another pedal, your pickups and your amplifier. When a pedal starts to interact with your tone when it is off, this is referred to as Tone Sucking. Circuits that are big culprits of this are Wah wahs and Fuzz pedals.
Tone sucking occurs when the input impedance of a pedal is too low. A simple way to think of it is that what has higher impedance also has most of the guitar signal. So, if the guitar pickup has relatively high impedance and the input of the next pedal has low impedance, most of the signal is across the guitar pickup. This means that the signal is not going where you want it. For a more detailed description, you can check out my guitar buffer write-up which talks about impedance.
If the guitar input is always connected to a circuit that has low input impedance, then when the pedal is OFF you will have loss of signal.
Why would I NOT want true bypass
Like all things, there are two schools of thought on true bypass. One side will tell you how great it is, and another will tell you something completely different. I think its important to understand both sides. A reason for not wanting true bypass is that if you have many effects with true bypass all put together with no proper buffers, eventually the stray capacitance of each one in the OFF position adds up to the point that they also start affecting your tone. This is kind of like having a very long guitar cord.
This argument is true but in my opinion, it is easier to control your effects and tone with all true bypass. . .Heres why. . Those that argue you dont want true bypass show that you can put a buffer in basically all your pedals. This buffer is always ON, even if you have the pedal in the OFF position. Boss pedals are a great example, they have buffers on all the time. Did you ever notice that when you use some of these pedals, you can hear a slight loss of treble?
If the buffer design isnt great, than no matter what you always have it in your sound. Additionally, each buffer will have a hopefully small amount of white noise, but these will all still add up. I want to note, always having a few buffers may not be bad. The legendary tube screamer has a buffer that is always on!
Why I think true bypass is always better
If you have true bypass and start to see some loss of your tone, then you can always add a buffer into your pedal chain wherever you want. You are not at the mercy of the pedal manufacturer as to where that buffer is. You can put it at the beginning or middle of your pedal chain to combat the capacitance issue. Plus, you can find the best buffer for you. Maybe it is really small, maybe it has high supply voltages for linearity, maybe you want an ultra low noise JFET design; you name it, you pick it. The point is, you are in control.
Quiz question – why didnt I say you can put the buffer at the end of the chain to combat the multiple pedal capacitance problem? The reason is that the capacitance appears before the buffer in this case and will already have removed some of the high frequency components of your tone. The capacitance is in parallel with the buffer input resistance and the lowest impedance dominates. However, a buffer is great at the end of your pedal chain if you have a long cord between your pedal board and your amp because it has a low output impedance and can drive the capacitance of the cord.
OK, back to the true bypass part. If all your pedals always have a buffer on, then what you will have is noise. All transistors have what is called thermal noise which is basically due to electrons moving around causing small currents or voltage noise. These noises are usually called white noise because there is no specific frequency. Think of that sound when you turn an old school TV on that isnt tuned in. As you start adding more buffers up, you get more noise. Most mass produced pedals do not have buffers designed for low noise.
If you were to have true bypass pedals, you could basically put a buffer once every few pedals and end up with a much lower overall noise than if all your pedals always had buffers on. Heres an example from the buffer write up page:
Figure 3. With true bypass, you can put a buffer where you need one if you need one.
Why are a lot of boutique pedals true bypass but other mass market ones are not?
Well, one of the main reasons is that for the most part, the switch needed to make a pedal true bypass is more expensive. A good DPDT (double pole, double throw) switch can run as much as $10, where a simple mass market SPST switch is maybe $2. Thats a big difference in the overall cost of the guitar pedal.
Have you ever noticed that neat little switch in a boss pedal that looks like a little plus sign? The design of the box and that switch saves them a ton! Usually, boutique pedals cost more due to the attention to detail and added features like true bypass.
Oh No, Some of my pedals arent true bypass – what should I do?
To be honest with you, if you like the sound than nothing, especially if it doesnt seem to make much difference when the pedal is off. If you want to test this, get some cables and your pedal. Its best if you have two short ones and something to connect them directly (you could either use a pedal with true bypass in the off position, or get a 1/4 to 1/4 adapter, guitar center and amazon sell Planet Waves Dual 1/4"" Jack Adapter which should work). Play with the pedal off and see how it sounds. Then, remove the pedal and replace with the bypass jack. If you hear a big difference, then the circuit is exhibiting tone sucking. I would do this with the pedal both in my actual pedal board and out with only two cords. One important point is that if you use long cords, then you might be getting into cable capacitance problems which might affect some of the tone as well. It is best to try this with a short 3ft cord to the pedal and a patch cord to the amp.
You can also mix and match. For instance, if you have a pedal without true bypass that has a buffer that is always on, maybe you want to place it in front of two or three of the true bypass pedals. That way, the buffer in the pedal without true bypass will drive the others. This might not work though if you place it in front of a fuzz. . . but let you ears be the guide which is the point!
Final Notes About True Bypass Guitar Pedals
Personally, I like all my pedals to be true bypass and all the ones I build at ScreaminFX have true bypass. I even modify my Crybaby Wahs to be true bypass by changing the switch and rewiring. The reason is that with true bypass, there is more control over what your final setup will be. I can make it so that there are buffers where I want them and otherwise I can have a nice clean signal. I dont like having to use extra pedals like noise gates! Like I said before though, its really up to you and what sound you want and like.