This is part 2 on overdrive.
So let’s take a look at the “transparent overdrive”. If we were to cut down the continuum from 0-11 to 0-2 or 1.5 and add a overall volume, the amount of noticeable waveform clipping would be hardly noticeable to the ear until the gain was almost all the way up. The actual waveform changes throughout the gain stages, noticeable note sustain, but the tonal characteristics are less audible. Hence the name “transparent overdrive” is given. A better descriptor would be “sub-audible clipping system”. The overdrive is present, but not a level that is discernable to most players.
Next, let’s take a look at a tube screamer circuit. I would gather the range for most of these is from 3 to 8 or so. On the low end, a somewhat clean boost can be had, but it can get very “clippy” and overdriven on the high end. The JRC-4558 chip is famous more that ‘mid range’ gain. The waveform clipping is again almost identical, it is that equalization (mid range) that gives this chip it’s characteristic tone. Again, let’s consider that some of the clipping from this pedal is how it interacts with the V1 preamp tube. That midrange frequency will interact with the tube much differently than the transparent overdrive I previously mentioned.
When we look at the TS-9DX pedal, it is the same type of circuit with higher gain. It pulls from a range from 3 to 9 9.5. As you can start to see, from overdrive pedal to overdrive pedal the differences are the range of gain and the tonal component of the circuitry. It is a difficult challenge to develop a circuit that would contain the entire continuum of drive from 0 to 11. Designing a circuit that did that would come at other costs, such as loss of high end or low end.
Finally, let’s explore a super high gain overdrive circuit. My favorite high gain pedals are the Creamtone Creamsiscle (Which I do not believe is in production anymore), and the PBT OD. Both on the scale run from 4 to 11. At the high end, clipping becomes harder and more harmonic overtones are heard. Overtones or partials are frequencies higher than the played frequency. As gain is increased, these subtle frequencies come out.