Headroom?

Sassafras

I understand what's meant by clean headroom when talking about amps but what does increased headroom mean when referring to OD or distortion pedals?
ie: when running them at 18v rather than 9v.
To my old ears there doesn't seem to be much difference.

77ric

I understand it to mean that the sound is a little clearer with better note separation, perhaps with increased dynamic sensitivity and allowing more of your natural tone to come through. I think it’s very much dependent on the design of the circuit in the pedal, while many 9v pedals will run at 18v not all will have that increased headroom. 

UnclePsychosis

I always assumed it meant much the same thing.

There's a point with dirt pedals where hitting them with more input doesn't make much difference to the output. I always assumed that that's what people meant. 

ICBM

It’s the difference between the signal level you’re using and the point at which it will clip, nothing more. If the signal is already clipped then it’s meaningless.

Running pedals at 18V can increase the headroom if the clipping occurs in a transistor or IC gain stage, but not if the clipping is done with diodes which have a fixed voltage.

That doesn’t necessarily mean the tone will be the same though - things like the slew rate of ICs (which affects the HF response) can be affected by the supply voltage, if I remember right.

Funkfingers

Sassafras

Thank you @ICBM ;
I had a sneaking suspicion you might be able provide a satisfactory explanation.