Stereo – mono dual, true stereo or dry thru?

Ask the DudeSome guitarists are using stereo rigs. But what is stereo actually?
In daily life a stereo sound is totally natural: via our ears we perceive a signal. The level of the volume varies according to the distance to the left or to the right ear. Therefore, we are able to indicate the direction of the signals’ origin. Additional reflections provide further stereo information.
Some time ago, I already released articles about wet/dry, analog dry thru and stereo rigs. In this case, the signal is led to two amps to create a stereo signal. But how does a mono guitar signal actually become a stereo signal?

Stereo effect pedals are built up in a different way and not every pedal with two inputs and two outputs is automatically a stereo pedal.

Dual Mono

In regards to a stereo signal, it is decisive, whether inside of the pedal the signal will be summed up and processed by one effect processor, or if two separate processors process the signal. This differentiation defines, in very simple words, the mono or stereo configuration. The number of the input and output jacks of a pedal does not matter at all.

True stereo

Some true stereo pedals are the exception of the rule by adding an effect to the signal of one channel. The stereo effect which is created by this, is subsequently, added to both channels. By this a true stereo signal is created although only one processor is used.
True stereo pedals two processors sometimes rotate the original signal 180 degrees to extend the stereo image.

Dry thru

Some effect pedals process the signal of both inputs as (analog) dry thru and add them to the effect signal. This can offer advantages as well as disadvantages. The dry thru signal might cause, if it has previously been processed by another stereo effect, phase issues as soon as it is added to the effect signal.

In practice

Actually, for guitarists it doesn`t matter if the pedal works dual mono or true stereo because even the mono sum will finally create a stereo effect. But if you use two effect pedals that do not create a true stereo signal in line and activate both at the same time, this might cause problems. The de novo summing of stereo information might lead to phase issues.