subterFUSE

I have been using the AUX Input in both my 545i and new 325i.

I have always encountered serious noise problems when using the AUX Input.

To begin with, the cigarette chargers have always induced severe alternator whine. But even when I disconnect the charger, there is still noise in the AUX. I think it might be the sound of the hard drive in the iPod accessing. Obviously, the hard drive spins inside.... and I think that noise bleeds in. Another problem might be a dodgy D/A converter. Apple iPods are not high-end audio gear, to say the least. They are disposable pieces of crap, which rarely last longer than about 2 years.

Part of the reason I notice the noise is because of the music I listen to. I listen to electronic dance music, like progressive house. This music is engineered to be played on the huge danceclub super-systems like the ones at the legenday Twilo in New York, or Fabric in London. The sound system at Twilo, which closed several years ago, was widely considered to be the best club soundsystem ever created. A sound system so incredible, that music producers from all over the world would literally write music just to be played at Twilo. Some were even naming their tracks after Twilo. The designer of the Phazon sound system at Twilo actually went as far as installing probes around the dancefloor area which sampled the air temperature and humidity, and relayed those figures back to the digital processors which controlled the EQs and Crossovers. So as the fog machines went off, and the room heated up and cooled down.... the sound system was adjusting its EQ and Crossover settings to optimum levels for the conditions.

Anyway, I listen to my music as loud as possible, volume all the way up as high as the car lets it go. Most parts of the music are loud, but during breakdowns the beat stops and there's typically a quiet passage for a minute or two.... before the beat comes back in. It's during these passages where you can really get a sense for the quality of a good stereo. While these breakdowns are quieter than the rest of the track, they still feature a lot of lush, ambient sounds and deep bass effects. When you listen to these sorts of sounds, at full volume, you can really hear the limitations of a audio system. Without the strong beat there is nothing to hide these limitations in equipment. A soft, but deep ambient bass tone can reveal a lot about your stereo. In the case of the Logic 7, I can actually hear the sonic artifacts which the poor processing creates.

So.... that's why I was asking for someone to test the iPod with full volume, on a blank audio file. Because that way we can test the noise floor for just the equipment itself. It could just be that the music I listen to is too much for the Logic 7 to deal with.

Now that I have created that file, I'm going to put it on my iPod, and also on a CD. I'll test them back-2-back in both my 325i and 545i.

Results coming soon.

Darron.Lowe

This is my understanding so i apologise for any inaccurate information...



Personally i doubt that there will be an issue with the noise purely because of the method of transfering sound. With the AUX in, you are taking output from the amplified headphone connector and that travels down the aux cable to the head unit past several points of interference (such as the cigarette lighter) to the head unit which then re-amplifies the sound.



With the iPod interfaces, you are taking sound from the line out equivalent down similar cabling (probably shielded) used for the cd changer to a head unit over a shorter distance.



I also believe that earthing of the iPOD will help (remember that it is powered from the car) whereas with the AUX in there will be some earthing issues (this is not a strong point so may have missed the point completely!



Hopefully this helps you.

subterFUSE

I do not use the headphone jack on the iPod.

I have a car charger with dock connector which uses the Line Output.

I also have a ground loop isolator which goes between the line output of the charger and the AUX input of the BMW. This does help diminish some of the alternator noise, but does not cure it completely.

Darron.Lowe

Oh well, still the cable from the CD Changer / iPod interface should be better quality and less suceptable to interference... 'As per' my last post

subterFUSE

http://www.mixdepot.net/subterFUSE/d...35/Silence.wav


OK Guys...

Here is a short audio file which is completely silent. Right-click the link, and Save Target As.

It is about 30 seconds long, in WAV format.


The best way to check it out would be to load it onto the iPod as a WAV, and then set the iPod to repeat loop play. Play the file, and raise the BMW volume control to full. Listen for audio noise... background hiss, buzz, or alternator whine. Step on the gas pedal and rev the engine a bit, and listen for noise... particularly a whining sounds that increases pitch when throttle is applied.


Report back.

subterFUSE

Thanks to fellow board member, Brian (Lab Rat)... who conducted the noise test with an integrated iPod adapter.

He reported no noise when using the silent test file I uploaded. No alternator noise, either.


So this is an advantage over a standard cigarette charger.