Aux-In ground loop

[sweeneyp]

an external DAC? It would work (And before I started looking up specs on the ipod classics DAC was considering it), but I'm not really willing ot spend $200 on a fix. Especially considering I got most of the noise killed by changing power supplies.

[AWL in]

Wow, this is a great thread and a problem I'm having with my 2010 HL limited w/ Nav. You mentioned a TSB. I can't find a TSB about this on any google searches I've done. Do you know the TSb number or link?

Also, you mentioned the TSB was a band-aid approach. Is the TSB a waste of time?

Thanks for all of the great tear downs , analysis and modification posts.

[sweeneyp]

Its TSB "T-SB-0085-08". Check your PM's. But it only applies to 08-09 HL's (Unless they revised it since I got the document).

The TSB is essentially the same thing as my audio cable with the transformer. Its a filter, but its installed behind the dash in series with the wire harness for the OEM aux in jack. I'm assuming its a 1:1 transformer, but it could be a simple cap in series to cut out the high frequency (along with a bunch of SQ).

[heartdisease]

By sq you mean sound quality? If so are you saying that my Cap I have pre amp in my system is costing me sound quality? I have always liked them as they sure can cut out alternator whine along with the power supply aspect of them.

[sweeneyp]

Yes I mean sound quality. But caps respond differently when installed on DC or AC circuits.

The cap you installed on the power line in your car is "smoothing" the DC ripple coming from the alternator. The power cap is passing any AC current (the voltage ripple in the DC signal) present in the DC 12v through to the chassis instead of your amp (since caps act like shorts in an AC circuit, vs a break in a DC circuit).

What I was referring to was a small capacitor wired in series with the audio wires (aka AC signals). It acts like a high pass filter. It would cut out all sound above a certain frequency. It would have to be a fairly low frequency to do that and could cut into the music as well. That's why they probably use a 1:1 transformer over this method, but it is a possibility.

[heartdisease]

Ahh so I am all good thanks for taking the time to clarify

[AVConsult]

Been meaning to post this for two weeks...

I had the iPod charger from my '02 in my wife's '08 for a Holiday trip. I noticed that the iPod Touch could be played through the car AUX port while charging. Quiet as...well enough over the top political posts for one night.

Anyway, no extraneous noise. I listened more carefully to the charging noise in my '02 and it appears to be a combination of alternator whine and digital hash, possibly from other things on the 12v bus. I plan to scope it (now that I can locate my scope) and make a filter to see if it can be eliminated.

Sweeney--the noise you described may be from grounding the AUX cable to your iPod case. Did you ever try isolating the 3.5mm plug shell from touching the iPod body?

[sweeneyp]

Originally Posted by AVConsult

Did you ever try isolating the 3.5mm plug shell from touching the iPod body?

Yep, zero change. The Ipod had a small plastic sleeve that stuck up above the shell a TINY amount to do that. But I tried it with a piece of electrical tape anyway.

At least what you found makes me think its dependent on device. I still haven't tried my phone while its charging, I should probably get around to doing that Considering the 160GB ipod classic is usually bought by people who have big library's and enjoy high fidelity (and high storage) music, you would think apple would have designed the circuitry in a way to try and minimize this issues. It sounds like they did it on your ipod touch.