Musicians often ask me if our products are "true" stereo. As if there is only one true stereo. Spoiler alert: "true" stereo is not a thing. There are different types of two channel processing: some are considered stereo, some are not really, and some can behave as stereo under the right circumstances.
First, when you have only one signal channel, it's easy: it's just "mono" (short for "monaural" or "monophonic"). No confusion here.
But once you get to two channels, it gets more complicated. So, I'd like to take a few moments to define some of the more common ways to process a two-channel signal.
Stereo. Wikipedia defines stereophonic sound, or simply stereo, as “a method of sound reproduction that creates an illusion of multi-directional audible perspective." A stereo processor should be able to create this illusion with either a mono (dual or one-sided) or stereo input. Signal is received from both inputs and processed in some way to create a stereo output. This implies a certain amount of coupling between the two channels, depending on the type of processing.
Dual-Mono is how I would define two discrete audio channels that perform identical (or not) processes on the input signals. With a stereo input, you still get a stereo output; but with a mono input, the output is still mono. It does not—by itself—create a "multi-directional audible perspective." Sometimes, this is called discrete stereo, but I think this is too easily confused with regular-old stereo. You could, in fact, send two completely different mono signals through this type of process with no interaction—hence the term dual-mono.
Mid/Side or Joint Stereo is a method of encoding a stereo signal into the sum and difference of the two channels. The output is not typically reproduced directly; rather, it must be decoded first. Sometimes, encoding/decoding is performed acoustically via clever microphone/speaker placement. The purpose of this encoding is typically to separately process the common and difference portions of a stereo signal.
Wet/Dry is mentioned occasionally among guitarists wanting to achieve separation between their dry (unprocessed) and wet (processed) signals. While this does create some amount of "multi-directional audible perspective," it is binaurally unbalanced. Therefore, I consider it to be distinct from stereo. There is also wet/dry/wet, but this is a 3-channel configuration that I won't get into here.
Blended is when a mono signal is split and run through two different signal chains in order to combine the effect of both. Guitarists sometimes run a guitar to two different amplifiers (without stereo processing). Bassists sometimes split their signal into clean and dirty channels. In any case, I think it's better to think of these signals as being "blended" together, either electronically or acoustically, into a new mono signal.
So, what about the "blended" case where where the signals are panned hard L/R? This is often referred to as stereo but usually lacks the "illusion of multi-directional audible perspective," in which case I tend to think of it as dual-mono where the two channels are different processes.
Many stereo delay-based effects (including ours) are in fact stereo, because their intent is to create a multi-directional audible perspective—even with a mono input.
On the other hand, our Iconoclast Speaker Emulator is more akin to a dual-mono processor when its Stereo Enhancer is disabled. However, when its Stereo Enhancer is enabled, it becomes a stereo processor (as defined above).
As you can see, there is no one "true" stereo; rather there are various methods of processing a pair of signals, each of which may be appropriate under the right conditions.