Hey everyone-

I have a 2009 C300 with the Logic7 sound system and the iPod integration kit. I also have the German-sourced iPod amplifier installed (I installed it myself and ordered it with the correct part number, so I know it's not the cheap amplifier).

When listening to classical piano music on my iPod (256kbps sampling rate) at high volume, I sometimes get distortion at a specific frequency from the driver's door tweeter. The dealer has replaced the tweeter.

Any ideas?

 

Remember that the iPod Integration kit takes the ANALOG input from the iPod. If the volume on the iPod is set above "8" (recommended EQ on the iPod set to "Pop") this may overdrive both the iPod Amplifier and/or the A/D convertor at the input of the headunit.

Try setting the iPod volume to "7", this has to be done with the iPod disconnected from the Merc of course, and see if this eliminates the distortion.

Another source of distortion is that many early CD's were recorded and produced by engineers that ran the signal up to its maximum digitalization threshold, not accustomed to having 110 dB of dynamic range to work with. These recordings, when reduced to MP3, even with a 256k sampling rate, can crash into the limits set, as one way MP3 compacts information is to greatly reduce dynamic range. Piano is very susceptible to this range reduction distortion, and orchestral strings will sound "strident".

If the MP3 sounds well on a normal system or through quality headphones, then reducing the iPod volume to "7" should solve this situation. Best of luck.

 

Thanks for the detailed reply! I'm wary of sub-par recordings (they can ruin the quality and enjoyment of classical music), so most of my albums were recorded in the past 10 years; hopefully the CD-to-mp3 conversion process was mature and standardized by the time they were processed.

One question about the iPod volume, though. I do have the iPod dock connector, not just the 3.5mm headphone jack, for my iPod kit. Does the iPod (2nd gen) actually allow you to adjust the volume and equalization for this specific output? I was under the impression that the output level and equalization were both fixed when the dock connector is used.

 

I also thought that with the iPod Integration Kit's provision of a standard iPod connector, that the signal would feed a digital input into the MB headunit. Logically, however, and as the iPod amplifier is also analog, even with the iPod Integration Kit, both the Audio 20 and the HK headunits prefer to receive and convert an analog input to the digital domain its own way. Surprisingly transparent the whole process, after suffering the distortion of the Chinese-sourced iPod Amplifier, once the German amplifier like yours was installed, I now cannot detect any sonic degradation. This allows, in the Audio 20, to have a parametric equalizer (no small feat), and of course the HK to perform it's Logic 7 surround sound magic.

The best iPod in terms of its analog output, some claim, is the 6th Generation iPod Classic. I am quite satisfied with mine and also use the same 160GB iPod Classic to drive (digitally) a Bowers and Wilkins system at home. All music is ripped Apple Lossless from original CD's. Even so, about one in 50 CD's have converted poorly and are distorted, these have to be imported again, and with about 800 CD's and 7500 tunes, re-importing these CD's is an ongoing project. So it is possible that what one trusts would be a stellar MP3, in fact has been incorrectly imported into iTunes.

iTunes, has "updated" their application, but I think the 11.x version is just terrible. Also, the iTunes Sync doesnt record the iPod's directory correctly, and even though I force iTunes to upload certain CD's onto the iPod, they fail to appear in the iPods menus. Quite frustrating.

Thus proving that not all is perfect in these technologies, however convenient, and are often subject to failure, both functionally and sonically.

 

On the same topic, does anyone know if there is any compression/loss when "ripping" a CD to the hard drive on the Logic7 system?

 

Hey op, whats the part number for the amp and how much did it cost?