XM radio FM transmitter
 

I was given an XM satellite radio and I hooked it up today. It's the kind that uses an FM transmitter. It works pretty good but it's a pain to get a good FM station so the sound is clear.
It's an older model that's discontinued I believe, but it's the XM roadyXT. On one side of the dock it has the power and FM input, on the other is a plug labelled "audio input." Can I just hook it up with an aux cable to my actual head unit (pioneer) and eliminate the FM garbage?
I realize it's just as easy to go try it myself as it is to post on here, except I'm on the computer right now and not in my truck... just seeing what anyone has to say!

I would definetely try it. Hard wire is always more clear then going through the air. It's like using a iPod on the aux cord compared to listening to the radio. AUX will always be more clear. As long as you have good signal on the SR of course.

So I tried using the aux hookup today over the fm transmitter. It worked! it does work just like an ipod. The sound quality is so much better! only thing that is just annoying is I have to turn the volume to 30ish for it to be sort of loud. If I have my ipod hooked up via a usb cable, a volume level of 15 is more than loud enough, put it to 20 and the subs make your hair stand up. Does anyone know why there's such a difference? Is it a setting that I can change? It's just annoying because if I switch from the satellite radio to FM radio to my ipod, I have to change the volume by 20 (first world problems, eh?)

It all has to do with the strength (voltage) of the output signal. Turn the volume down on your iPod and you could match it to the output of the XM receiver. (Obviously you don't want to do that I was just stating a fact)

See if the XM receiver has a volume/output level that can be adjusted. If not then there's not much you'll be able to do for it. Most devices that deal with FM transmitters have a fairly low output level because those transmitters will heavily distort a very loud signal over the FM transmission.

The XM receiver did have an output level. I turned it all the way up and it helped a bit, but there's still quite a difference. I don't know the technical words, but does a USB carry the signal better? What if I got an aux to usb adapter, would that help at all? I ask because with my ipod, the sound is louder if I have it connected via a usb cable as opposed to an aux cable.

With the iPod it's not using an audio signal. The music files are being played directly through the stereo from the iPod. Just like playing the song in iTunes on your computer. There's nothing you can do to connect the XM to the USB. Any USB audio adapter to get an audio signal in through the USB device won't work on the HU like it will on a computer.

The only other option would be a headphone amplifier like the Fios ones sold at PartsExpress. They have the 1/8" stereo headphone jacks in them and amplify the signal that passes through them.

Oh I understand now! The XM is playing the music and the aux cable is basically relaying the signal to the head unit and therefore through the speakers. Whereas the ipod is acting as a storage device for the songs that the headunit accesses via the usb cable? So playing music from an ipod with a usb is just like playing music off of a CD?
This might be a stupid question, but as far as the amplifier, does it actually improve the sound quality, or just make the sound louder? Or does that depend on multiple things?