True Bypass and Guitar Pedals

The Basics of True Bypass

The easiest and simplest way to describe what true bypass means, is to say that if all the effects in your chain are true bypass, then when you have all of them off, the signal running from your guitar to your amp is not effected by any of the inner circuitry of the pedals.

That is to say, the tone produced when all true bypass pedals are switched off should be the same as it would be if your guitar was plugged directly into your amp. Of course, there are some technical aspects of true bypass that needs to be understood to get a true grasp of this technology and what it can do for you.

The Switches Behind True Bypass

• Double Pole Double Throw (DPDT) Switch – True Bypass

To achieve true bypass, an effect pedal must be equipped with a special switch to ensure that the original signal will remain pure (un-affected) when the pedal is switched off. Most true bypass pedals use a DPDT switch. What this switch does is toggles the signal coming from your guitar either into or out of the circuitry of the effects pedal. DPDT switch pedals require a special sensing circuit to toggle an LED on and off.

• Triple Pole Double Throw (3PDT) Switch – True Bypass + LED

A 3PDT can be found in many boutique effects pedals, and essentially does the same thing as a DPDT. The difference comes because the 3PDT has the added feature of lighting an LED when it is switched to true hardware bypass. As far as the signal, it is affected (or, unaffected) in the same way as it is when using a DPDT.

• Single Pole Double Throw (SPDT) Switch – not True Bypass

A SPDT is essentially the opposite of the two above switches in that it is not true bypass. When a switch of this kind is used, the original signal is run through the circuitry of the pedal regardless of whether the pedal is switched off or on. Therefore, when the guitar signal reaches the amp, it will be affected even if the pedal is off. More specifically, the signal will suffer from high end loss.

With the above information, it would seem that there would be no reason not to purchase only pedals with true bypass switches. But there are considerations to be made regarding true bypass and a couple of things guitarist should be aware of when building a pedal board.

The first thing you should be aware of when using true bypass is that you can still lose signal (volume) through your chain. If you have an extensive effects setup, and particularly if your pedals are a considerable distance from your guitar and/or amp, signal can be lost as it travels through the circuitry of the pedals and the length of guitar leads.

One way to overcome signal loss is to use a (send + return) loop / signal routing pedal. This is when you "loop" certain effects together in your chain, and use a true bypass routing pedal to not send your signal through only certain loops / pedals.

Using a loop / signal routing pedal is also a great way to segregate non true bypass pedals out of the signal chain, and bring them into the chain only when required for the actual effect. Another way to overcome signal loss is to add a boost effect to your chain.