IPhone – How to adjust siri’s volume so it will sound louder via earpod

I don't have an answer, but I have the identical problem with an iPhone 3G. The sync system will recognize USB for about a month and then start failing until it flat out won't recognize anything device that is inserted into the USB port. I've had the guys at the dealership look at it 3 times and each time they get it to start working again by upgrading the sync software or it just happens to start working.

Have you found a solution beyond using Bluetooth? I can't even charge my phone anymore through the port.

This question might be hard to answer without some rigorous definition of distortion and qualification of what amount of harmonic distortion is permissible - let alone some clue as to what signal is being played.

In general, the headphone jack is desired to distort sound. Whether its muted or amplified, the output isn't what the recorded sound actually is.

Have a look at these threads fr background:

• Why do I get "no volume available" when using an iPhone 4s in a dock?
• Stop high frequency noise from iPhone dock's line out in car adapter

So - you could get an adapter that generates a line-out level signal and control things from another amplifier or you could experiment with signals you choose and find a setting that doesn't sound distorted to your ears. My guess is most people would set the volume a 60% for most commercial pop music and perhaps a little higher for softer music that isn't compressed so aggressively as pop music.