Ok thank you both for your information. I think I understand your responses specifically when it comes to blindly wanting to increase the supply voltages for these circuits. While I want to increase the headroom, I am not just trying to increase the supply voltages blindly. I guess the information you provided is to suggest that increasing the headroom on a pedal above 9VDC is not necessary at all. But neither is a 600 horsepower motor in a Corvette when you can only drive 65MPH…
For this I am really just concerned with having enough headroom on the fundamental tones of a bass guitar specifically for the lower strings which have higher voltage levels in their output. While it may not seem necessary, the bass guitar that he uses has a preamp which is running from two batteries and has a headroom up to 18VDC. Why wouldn’t the player want the remaining path have similar headroom?
So my objective is to ensure that the path for the fundamental tones has as much headroom as possible. And I am also thinking of adding high pass filters for the 2nd (OD/Fuzz) and 3rd (Chorus/Phaser/Flanger/etc) paths so perhaps the pedals operating on the higher frequencies will not require 18VDC. I get that.
So in general, the OpAmp based circuits using 18VDC that would carry the fundamental tones would likely benefit (at least in theory). In my example, I may opt to run the Paramix and BuffN Blend at 18VDC while running the rest at 9VDC.
FY, that I see that the preamp/eq section of the GK bass head he will use has power supply circuit of +/- 15VDC. The power amp section is at higher voltages as well. Here is a case where the 500W power available to the GK head is analogous to the 600HP Corvette. You may not need 500W to power the stage when the guitar player has a 22W Deluxe Reverb. But having the headroom makes sure that the lower frequencies will not clip. Driving to the bank in a Corvette is much cooler than a Pinto!
I do understand that the BJT and FET based circuits used in the overdrive and fuzz PCBs can not just automatically use a higher power supply voltage without having their input and output bias voltages being adjusted to support more symmetrical operation. So I may start with the Paramix and BuffNBlend and analyze it under the player’s load using a scope and see how it lands. Maybe it will be a waste of time. We’ll see.