Stereo not working so well...

[danmurphymn]

I have a 2002 540 touring with 220k on it. New to me as of a few months ago.
When I got it, the PO said the amp was out so he pulled the fuse. When the fuse was put in, there was a constant buzzing sound from the speakers. I put a new (used) amp in, DSP and now the radio works. But... not well. The sound is pretty low and it'll play somewhat normal, then lose a lot of volume and play pretty quiet. The DSP light never comes on. I plan to check the antenna connections but I finally tried putting a CD in and it does the same thing so I'm thinking it's not the antenna connections. Thoughts??

[computiNATEor]

Try a new radio module. If the DSP amp is known to be good, then I'd suspect the radio. The radio/MID communicate with the amp to control volume, IIRC. Paging DennisCooper...

- - - Updated - - -

Obviously, check the amplifier and radio connections. Check your power and ground sources, and check your wiring as much as you can. The diagrams available on newtis.info or BMW-planet.net may help.

[BimmrMeUpSnotty]

The DSP amps are known to have cracking solder points on the boards. My wagons DSP amp's first dying signs was loosing the highs, and the music just got sadder and flatter, then got a buzz coming out of the little subwoofer in the right rear quarter that the wagons come with, then the pile of crap finally crapped out. I'm wondering if anyone has tried opening the amp up and re-solder the connections on the boards around here?

OP, if your DSP amp came from an E53 or an E38, the amp will need to be coded to E39, if it came out of an E39, it should be plug and play. But your symtoms are what it sounds like when you pull one out of an X5 or a 740. Find out what you got from the seller. If it came out of an E39, then maybe he sold you a bad amp.

[edjack]

DSP light? What is that?

[BimmrMeUpSnotty]

The LED next to the DSP button on the mid.

[danmurphymn]

Thanks for the help. The amp I got was from an E39.
I would imagine that the amp was good since everything started working again after I installed this one. I'll look into the radio module when things get a bit warmer. I appreciate helping point me in the right direction!

[DennisCooper]

Hi Danmurphymn,

Not sure any electronics specialists have opened up the OEM DSP amplifiers to see if they can overhaul them, I'm sure by now on the many BMW forums anyone or specialist company that had would have been known about and mentioned in topics like this. BMW didn't release schematics for the internals of the audio modules, knowledge that is out there mainly has come from 'higher level' repair specialists where certain components can be sourced. I think with the lack of overhaul for the DSP amp, the main components that do begin to fail aren't available etc.

For now until that changes, you'll need to source a known working DSP amp, have it coded to your car if needs be and 'cross your fingers' it lasts a long time. Chances are it will fail sooner or later and you'll be back in the same position as now.

Cheers, Dennis!