Running on 18 volts ??

[Mark Hammer]

Well, diodes do behave a little differently, depending on the current presented to them.  Perhaps they behave a little bit differently with a higher supply voltage applied to the op-amp pushing them?

It's one of those things that really cries out for a blind test.  Personally, I don't expect anything particularly noticeable, but distortions are an especially nuanced thing where very small differences can appeal to, or discourage, different players.  Of course, those "little things" can be a real and reproducable phenomenon, or they can just as easily be a quirk of a particular unit and the listening biases of the player.

[mac]

Well, diodes do behave a little differently, depending on the current presented to them.  Perhaps they behave a little bit differently with a higher supply voltage applied to the op-amp pushing them?

That's what I think.
Imagine a 1k resistor in series with a led at 9v. It's going to give some light. Now double the voltage keeping the 1k resistor. There is more current, more light and extra voltage drop.
For simplicity take a Dist+. At 18v the opamp and the 1u tant cap are feeding the diodes with extra current because like in the example above, the opamp and the cap can go higher. They make the diodes work harder, which means more harmonics, ie, more signal and more volume. It's not much because that extra diode voltage drop is small, but it is noticeable.

mac

[GGBB]

Just check the opamp datasheet.If it can take 18 vols it's fine.That opamp can take 18 volts.

If the max supply voltage for the op-amp is 18V, and you are feeding it 18V, isn't there a danger either that a mild surge in power could fry the IC, or that the IC is not bang-on spec and can only take 17.5V so this also fries it?

[induction]

If the max supply voltage for the op-amp is 18V, and you are feeding it 18V, isn't there a danger either that a mild surge in power could fry the IC, or that the IC is not bang-on spec and can only take 17.5V so this also fries it?

A max supply voltage of 18V means +/-18V, so it can handle 36V total. So it's not a problem.

[HOTTUBES]

When i do up another run of overdrives , i'm going to " beef up " the caps , and try one at 18 volts .... i have heard so many guys rave about how much " better" they sound running on 18 v v/s   9 v.  For some reason i could see players who use there overdrive to push a dirty amp enjoying the new found 18 volt head room etc .  

[HOTTUBES]

Thanks for everyone's input !!

[mac]

I ran a LTSpice simulation of a Distortion+ at 9v and 18v. Input signal is 0.5v @ 440hz.
First second is the output wave at 9v, then at 18v.
The volume change is "similar" to what I hear in the real life.
LTSpice shows a difference of 15% using 1n5817.
Even increasing the ouput resistor to >1M the difference remains the same.

sound sample

mac