Let’s compare the original BOSS DS-1 with my modified DS-1, so we check out the difference in tonal character between a distortion pedal and an overdrive pedal (or whatever DS-1 has become after being modified in https://electric-safari.com/2019/03/17/turn-a-boss-ds-1-into-a-nice-overdrive/).
I have tested them using a Linux computer, its sound card and qloud software. I know the measurement is not very precise, but the real thing is not going to vary very much, I think. All controls were at noon during the measurement.
Original BOSS DS-1
As expected from a pure distortion effect pedal, frequency response is mid scooped, with a bump at 100Hz.
Modified BOSS DS-1
As I expected after the modifications in the tone stack, frequency response has much more mids. The maximum is not at 800Hz, just because the circuit is not only the tone stack. By touching the tone control, the curve can be modified (I leave it for a next article).
As you can see also, at aproximately the same “level” value, the overall volume is higher (over -60dB for a wider range in the test), without changing any measurement parameter, even if the perceived distortion is higher in the original unit. The reason, I guess, is the red led in the clipping section instead of a common diode, see the article https://electric-safari.com/2019/03/17/turn-a-boss-ds-1-into-a-nice-overdrive/. Since the Vf of the led is higher than that of the diode, it clips at a higher voltage, giving the circuit more headroom. This is very common when doing this kind of modifications. I think the tone stack change alone does not explain that higher volume.