iPod squeal plugged into dig effects box

[Uncle Thor's Hamer]

I use a Pandora PX4 digital multi-effects box with headphones for quiet practice when traveling. Both of my iPods have a high pitched squeal when plugged in. I presume it is a digital sampling issue. The iPods are fine when plugged into earbuds or the analog input to an audio system.

Is there some setting on the iPod which would kill this sampling noise?

I can use my Android cell phone but it doesn't have the storage capacity or small size of the iPod.

My next cell phone will be an iPhone in another year or two unless it has the same issues as the iPod

[JohnnyB]

I use a Pandora PX4 digital multi-effects box with headphones for quiet practice when traveling. Both of my iPods have a high pitched squeal when plugged in. I presume it is a digital sampling issue. The iPods are fine when plugged into earbuds or the analog input to an audio system.

Is there some setting on the iPod which would kill this sampling noise?

I can use my Android cell phone but it doesn't have the storage capacity or small size of the iPod.

My next cell phone will be an iPhone in another year or two unless it has the same issues as the iPod

How are you connecting the iPod to the Pandora? Are you using the iPod's headphone jack to the Pandora's mini-plug input marked AUX? The PX4 owner's manual says, "If a CD player or other audio source is connected to AUX jack, you can play along on your guitar with a tape, etc. However the volume must be adjusted on the connected device."

Have you tried turning down the iPod's volume? It may be overloading the Pandora's input stage. If that doesn't fix it it may be an impedance mismatch. Unless your iPod is malfunctioning, there should be no sampling noise coming out of its analog headphone jack. Digital sampling noise would be above 22 Khz, which is inaudible to most of us. In a properly functioning D/A conversion, sampling noise is unequivocally filtered out of the analog stream.

[Uncle Thor's Hamer]

Yes I am using the aux in to the PX4 from the iPod headphone jack. The iPod volume has to be up to 50% or more in order to match the guitar signal. Also, the noise is there even when there is a silent passage in a song on the iPod. So louder is better to drown out the noise.

Impedance mismatch makes sense though it is a poor design on one end or the other.

[JohnnyB]

Maybe you should try a cable like this to connect your iPod to the Pandora. The dock end of the cable extracts the line level signal from the iPod's dock socket as well as the USB that you can connect the iPod to an AC adapter to keep the iPod powered up.

The line-level-to-mini connection gets the straight line signal out of the iPod, bypassing the iPod's internal op-amp used for volume control. It could make for a better matchup, and there would probably be less noise in the line.