How True are True Bypass Claims?
The great "true bypass" debate has to be one of the most popular topics out there on the numerous internet forums about stompboxes, and almost all stompbox manufacturers use this term in their advertisements – sometimes using very creative terminology. But do we really need to worry about our effects when they're not engaged? Is the true bypass craze just a hype tactic, designed to allow boutique pedal manufacturers to charge tidy sums of money for their products, and for guys to be able to make a living modding effects? As usual, you have to decide this for yourself, but I think it's time to have a closer look at what true bypass really means, what it does (and doesn't) do, and of course, how to determine if a pedal is really true bypass or not.
1. What is true bypass?
Simply put, it means that the signal passes straight through the box – directly from the input to the output jack, touching only the switch/relay – when the effect is bypassed. This kind of bypass arrangement is only possible with some sort of mechanical switching – either with a good old stompswitch or with an audio relay. The switching is done simultaneously at the input and the output, to route the signal around the electronics in the effect, and when bypassed, the box is completely disconnected from the input signal.
This is important, because as we will see later, this is a simple way of knowing if the claim that a certain pedal is true bypass is true or not. True bypass switching can be wired inside a pedal, or inside a separate true bypass box that the pedal connects to. In that instance, the pedal is kept constantly active, and the signal gets routed through or around it from the box. So always keep in mind: true bypass means that the circuit is physically disconnected from the input jack/bypass line. If a pedal doesn't do this, it is not true bypass. Period!
2. How do I know if a pedal is true bypass or not?
You often hear people wonder if their such-and-such pedal is true bypass or not. Sometimes I wonder if this is the same “I need to know" urge that makes us want to know if the fridge light actually goes out when we close the door. My personal point of view is that you only need to worry about it if you notice a degradation in your tone. Basically, if it works, don't fix it. However, if you just have to know if your pedal is true bypass, read on. Here are some of the fallacies you can often find on the Internet:
If you take the battery out and it still works in bypass mode, it's true bypass.
Ouch. All the battery-out test will tell you is if your pedal has a mechanical switch that carries signal or not, and if there are any active electronics in the main signal path. When the effect is powerless, the bypass line will of course still function as intended, but the effect input is still attached to it. No true bypass there. If your pedal has a buffer stage in front of the switch, or if it has electronic bypass switching (such as in Boss/Ibanez-type pedals), it will of course not pass any signal when powerless. But, again, you cannot use this test to verify that a pedal is true bypass – only that it isn't.
You need a 3PDT switch if you want true bypass and a status LED.
Sometimes you can read this mistake the other way round: if your pedal has an LED and doesn't have a 9-pole switch, it ain't true bypass. That's simply wrong, so forget it! Granted, for me, the easiest way to add an LED to a switching system would be to add a third row on the switch and run it from there. But the truth is that you don't need to redesign the whole circuit to accommodate an LED to indicate on/off status. Even an “aftermarket" true bypass mod with LED can be done with a DPDT. It's called the Millennium Bypass and was invented by R.G. Keen from Visual Sound [R.G. Keen does write our monthly “Tech Views" column – ed]. If the amount of components and effort needed to make it work is worth it is another debate. Personally, I''d recommend you go for a 3PDT switch if you absolutely need to add an LED, especially when you are just entering the world of DIY true bypass modifications.
In bypass mode, the circuit is electrically invisible, so therefore it is, in effect, true bypass.
In theory this one is actually correct. If the circuit's input impedance is sufficiently high, it shouldn't even register to the signal. As we know, current will always choose the path with the least resistance, and if we can make the path leading to the amp that much more inviting than the path leading to the effect, it would qualify as a true bypass (since none of the electrons will choose to veer off into the effects circuit). But in real life, this doesn't seem to work. There is no scientific proof of this – only lots and lots of observations where effects that are supposed to be “invisible" in bypass mode still affect the tone.
If you really want to know if your effect is true bypass or not, you have to open the pedal and trace the circuit. That's the only way to find out where the signal goes and doesn''t go when the pedal is off. You can use an ohmmeter to measure this, but you still have to do some circuit tracing. Locate the input to the circuit (on the circuit board), and the main input point on the input jack (you can use a patch cable in the input jack for this). Measure the resistance between the two points while you press the switch – if you get zero resistance in both switch positions, the pedal is not true bypass. A true bypass pedal will disconnect the circuit input from the main input jack in bypass mode, showing up as infinite resistance on the meter.
Measuring straight through (from input jack tip to output jack tip) will not show true bypass – it will only reveal the same things as you'll learn when pulling the power.
3. Will an all-true bypass rig cure the tone sucking in my signal chain?
Removing your pedals from the chain when they're not in use will not only get rid of tone sucking but it will also remove their buffering (their ability to drive long cables). This means that the amount and quality of cable between the pedals and amp will have a greater impact than before on your tone.
While I was recently A/B testing a true bypass-modded CryBaby, I was struck by the amount of treble I lost whenever I had the wah in the chain – quite contrary to what the mod was all about. After a while it dawned on me that the difference in treble response came from me not only unplugging the wah to go straight into the amp – I was also unplugging some 5 meters (about 16 feet) of cable, giving me lots more treble. True bypassing your pedals might therefore send you into another tone-hunting frenzy, this time looking for the cable with the least capacitance. George L's, Klotz GY107 LaGrange or Sommer Spirit cables work great for this purpose, by the way.
The best compromise would be to have a really good buffer at the start of the chain (or as early in the chain as fuzz pedals will allow you to), with the rest of the pedals being true bypass. That will give your guitar pickups a consistent input impedance to work with, while the low impedance output from the buffer helps drive the long cable to the amp. Some like to have another really good buffer or slight booster at the end of the chain, and that is also an option.
Keep in mind that you don't absolutely have to buy a dedicated buffer unit – while they are generally quite good, they are also generally quite expensive. If you have a Boss/Ibanez-type (electronic bypass) pedal that you like the sound of even when it's turned off, it will do the job just as nicely. Personally I use a DIY buffer right in front of my pedalboard and it works great. Another interesting article about this is from Mr. Pete Cornish himself, if you are interested, you can read it here.
Next month we will keep on talking about true bypass and how to use it. Until then, have a good one and stay tuned!
Dirk Wacker has been addicted to all kinds of guitars since the age of 5 and is fascinated by anything that has something to do with old Fender guitars and amps. He hates short scales and Telecaster neck pickups, but loves twang. In his spare time he plays country, rockabilly, surf and Nashville styles in several bands, works as a studio musician and writes for several guitar mags. He is also a hardcore DIY guy for guitars, amps and stompboxes and also runs an extensive webpage singlecoil.com about these things.