Battery vs Power Supply

[Phend]

THANKS Jack, you have answered the question !!

[Lino22]

Has anybody succeeded in measuring the dying battery impact on the dynamics?

I did a lot of battery measurements and came to the conclusion that battery effects in fuzz pedals is due to the lower voltage of used batteries.

More reading: 9v Battery Impedance

Best regards, Jack

So no DC Voltage swings with hard notes? That's what i failed to see on my scope ...

[amptramp]

If you are looking at a Fuzz Face, the original version had no filter capacitor, so any impedance in the supply meant that there would be feedback from the output stage to the input stage and neither stage has hardly any power supply rejection at all.  Any power supply variation comes through almost at full strength and this can cause interesting effects.

[amz-fx]

So no DC Voltage swings with hard notes? That's what i failed to see on my scope ...

No voltage swings. A fuzz will pull basically constant current (class A), and very little of that. It's not asymmetrical enough to make a difference and the current draw is so low that it has practically no effect.

The sweet sound of depleted batteries is due to lowered voltage. Also, effects pedals usually have a big value capacitor as a filter on the dc voltage input. This capacitor acts as a reservoir that can supply power for a sudden demand when a strong audio signal hits the circuit. The cap will smooth out minor fluctuations in voltage/current. http://www.muzique.com/news/there-is-no-sag-in-fx-pedals/

regards, Jack