Low volume output on some guitar pedals

[Zipporello]

A stupid question from a stupid man:

sometimes i'm unable to check my pedal with real intruments, like guitar or bass guitar, so i plug in my ipod with a random song.
well, in some pedals, (the ones it doesn't have the volume control) when the effect is on, the output volume is a little bit low than the effect is off (truebypass).

is it normal? (maybe 'cause the input signal/impedence of an ipod is very different from a guitar?)

don't kill me, please 

[PRR]

> in some pedals

Which pedals?

Not just "doesn't have the volume control"; what do they do?

[Zipporello]

> in some pedals

Which pedals?

Not just "doesn't have the volume control"; what do they do?

like noise gate.

[anchovie]

Can you confirm the output voltage swing of your iPod, or that the same thing occurs with a real guitar? If your iPod signal is bigger than the maximum swing that your active components allow through then your pedal is going to be acting as a limiter compared to the bypassed signal.

Impedance shouldn't be an issue if the first stage of your pedal is a buffer.

[Mark Hammer]

The purpose of a nise gate is to turn the volume down automatically so that no one has to listen to noise turned up loud.  Some gates operate in all-or-none fashion, while others use what is called "downward expansion".  That is they exaggerate the difference between sort of quiet and a little bit quieter.

If the signal you are feeding the gate from your iPod is not enough to turn the gate "on"/open, then what you may be hearing is the gate treating your iPod as a quiet signal that needs to be turned down more.