I use my iPod in out TCH through the AUX jack and I have to have the IPod volume on max as well. There is clearly a gain issue through the AUX jack, if you don't the source device at max volume it forces you to crank up the volume on your stereo. What this does is drives the amp harder even if the sound coming out is quite...the result is that you get above the noise threshold of the amp and you get the hiss. The only real solution is to boost the output of the source device.

 

I have the XM My-Fi and I also had the Pioneer Inno. Both I would plug into the 12V and then come out the Line Out port of the receiver then into the THC Aux Audio port. I will get this terrible hissing noise. I would then unplug the 12V power source and the hiss would go away. Brought the car into the dealer and they confirmed the problem. Told me that Toyota was working on it and there was a Tech Bulletin on it. However, they did not have a solution for it. The problem seems to be interference from the Plasma Cluster/Ionizer with the 12V input. The hiss is transferred to the audio system. This is a real bummer. Basically if you plug any audio device into the Aux port with no 12V power you will be just fine. But one you plug your device into power while connected to the AUX port the hiss is there. Anyone else have this problem? Any homemade solutions until Toyota comes up with a fix?

 

Problem, yes...solution, no.

I use my iPod Mini through the Aux port and there is a definite hiss when the iPod is also plugged into the 12V power outlet in the center console. I just run it without the recharging cable, and the sound quality is just fine. I set the iPod for about 75% sound output level, and I don't find I have to "push" the volume on the car amplifier. The signal/noise ratio is very good with this setup.

When I first noticed the problem with playing the iPod through the Aux port while charging, I assumed that it was some sort of RF interference caused by not completely shielding the recharge cable. But that's a total guess.

 

I am not over driving the car amp due to having the volume at about 7-10 level. What I am talking about a hiss that is devloped when you plug in the 12V power source. It is noticeable. But I have heard what you are talking about in other cars. Thanks for the input.

 

I have a MyFi and had the same noise (well, actually, I HAD since the dealer finally got the XM OEM radio for the TCH Nav system and I switched to it).

I purchased a "ferrite bead" (the clip-on version of the big fat thing that is on many power cords). A few wraps of the power cord through it and the audio improved greatly.

By the way, the integrated XM has great audio quality, but I miss the ability to scroll through the channel names to tune and miss the scrolling sports scores -- neither are supported by the lame user interface on the Nav display.

...oh, well, isn't satellite radio about sound quality?

 

I solved the issue on my TCH by installing a ground loop interference filter (GLI filter).

This is the one that I use:
http://www.crutchfield.com/S-AjKLAyV...er&i=127SNI135

Works like a charm.

There is another thread about this somewhere, btw, but it is probably buried.