Amplifier Wiring

[revtor]

m6bigdog is indeed correct. The later amplifiers have a complete different design and are true 10-channel amplifiers.

For those who don't believe the BMW marketing information, let's have a closer look inside:



Attached to the large heat sink you can identify five "transistors". When we remove the clamp of one and take a close-up you'll see the following:



The "transistor" in question is a TDA7374B - an integrated circuit amplifier (link to datasheet). Each TDA7374B has two input channels and each channel has two opposite-phased amplifiers to drive a speaker - a so-called bridge setup. With five TDA7374B on the printed circuit board, that means 10 input channels and 10 bridged outputs.

[e31yausta]

I checked my amp wires on my 94 840ci. The black and white amp connectors look the same, but the different color wires are not at the same location for some reason. All I'm trying to do is run a sub but to keep everything else stock. I just want a little bit of bass to make the factory deck sound better.

This is the rca cable I have (just a sample). Obviously I have 2 that need to be plugged onto my aftermarket amp (both red/black rca). But the wires from the other end of the rca cable, where do I attach each wire to if based on the amp diagram of the connectors from the first page?


Not sure if this would work, but on the red end of the rca cable I'm thinking to attach 1 wire to the yel/grey-LR spkr gnd (-), and the other wire (+) to the yel/red-LF kick spkr. And of course on the black end of the rca cable I'm thinking to attach 1 wire to the blu/gry-RR spkr gnd, and the other wire blu/red-RF kick spkr.

Does this sound right? I'm so use to attaching the rca cable directly to the speaker's neg/pos terminals.

[wardhill]

Just want to thank TTTxgreg and this forum . I've been sorting through a mess of wires in the rear trunk trying to get radio and amp back to stock. PO had cut and discarded the two 12 pin connectors to the amp. The section of harness I bought from a salvage yard with those connectors was wired differently( although from an 850). Thanks TTTXGreg for taking the time to road map how the connectors were originally wired and after a lot of head scratching I got it back in working order. Very pleased with the sound too. Last remaining concern is a dull screen on the head unit. . Pixels are good , just hard to read in bright sunlight. Is there a fix for this?
Thanks again
Jeff

[xelaber]

I just did this. Let me assemble the info/pictures and I'll post later tonite.

I have a 1995 850i I want to replace the amp in the trunk and still keep the original harness I want to solder a new harness and bring it to a aftermarket amp. Reading your post I see you did the same thing. I do not see the photos in the post and wonder if I you still had access to those photos.

[PabloRock]

I think my amp is dead and would like to try the same. Not looking to put in a new system, just get some sound out of the stock unit. I have an amp laying around, so worth a shot if possible. Right now I can hear the radio if I turn it up all the way and listen carefully. No stereo expert, but I am guessing it's because of no amp (checked the fuse and it's fine). The $0 option would be great for me right now. (unless anyone has any other suggestions).

[m6bigdog]

I think my amp is dead and would like to try the same. Not looking to put in a new system, just get some sound out of the stock unit. I have an amp laying around, so worth a shot if possible. Right now I can hear the radio if I turn it up all the way and listen carefully. No stereo expert, but I am guessing it's because of no amp (checked the fuse and it's fine). The $0 option would be great for me right now. (unless anyone has any other suggestions).

Not that simple!!
The stock early model 4 -channel amp as well as the later model 10-channel amp have internal crossovers that perform the necessary function to sent the correct power and frequency range to the individual speakers in the system.
Without the crossover the full low frequency power (woofer power) from the amp will blow the mid and high frequency drivers.

Used E31 amps should be available.
If you can't find an E31 amp an early 4-channel amp from an E32/E34 or the 10-channel amp from an E36 with the same connector configuration will work although not ideal.

[PabloRock]

Didn't think it would be that easy. Guess I will have to search one out. Thanks.

[cartoonz]

I *might* have an amp still that fits the earlier cars. Let me look and see.

[PabloRock]

Cool. Let me know.

[tangcla]

Simple question, hopefully - what year did the 10- channel begin, or is there an option code in the VIN list that can identify this?

For what it's worth, my VIN (CC11063) has S676A (HiFi Speaker System).

[m6bigdog]

Simple question, hopefully - what year did the 10- channel begin, or is there an option code in the VIN list that can identify this?

For what it's worth, my VIN (CC11063) has S676A (HiFi Speaker System).

It may depend on the model radio installed and the country?
S676A is a 10-Channel amp HiFi system
In the US the 10-channel amp was installed in the 1994 840/850 models so I assume an after 9/93 build.