Yet another "bypassing the amplifier" question...

[onZedge]

This has been covered to a great extent on many BMW 5-Series BBS's. However the subject amplifier is virtually always the amp/crossover with the removable amplifier daughter board. I have the amp/crossover with the monolithic combination. Does ANYBODY know where I can get a copy of the schematic wiring diagram for part number 65.12-8 350 407? I have searched the Internet literally to exhaustion trying to find this document with zero results. Text language does not matter.

OR

If anybody has successfully bypassed this monolithic amp, PLEASE share how you did it!!

[jgardia]

Hi,
I've been playing arround with the circuit of the amp, I have some ideas that I'll try this week, and I'll let you know how it was.

Cheers,

Jose




This has been covered to a great extent on many BMW 5-Series BBS's. However the subject amplifier is virtually always the amp/crossover with the removable amplifier daughter board. I have the amp/crossover with the monolithic combination. Does ANYBODY know where I can get a copy of the schematic wiring diagram for part number 65.12-8 350 407? I have searched the Internet literally to exhaustion trying to find this document with zero results. Text language does not matter.

OR

If anybody has successfully bypassed this monolithic amp, PLEASE share how you did it!!

[Robert K]

I also have a 1991 535i with about 155K miles on it. When I revamped the stereo system in my car, I just took the stock amp out and ran the stock stereo cable to my new amp. My understanding was that the factory head unit put out line level signals, which I ran to the line level inputs on my new amp. The hardest part was just deciphering which wire carried which signal (e.i. which was front, left positive, etc.). Eventually, someone on another board even gave me the matching connector with pins that mated to the factory stereo harness. I wired that connector up to my new amp and then just plugged it into the factory harness once I had mounted the amp. Made for a very nice installation.

I don't have a schematic of the amp itself, and I'm sure it would be hard to come by. However, I do have a schematic showing which wires from the radio carry which signal. Send an email or PM to me if you want that schematic and I'll get it to you sometime this evening.

Grace and peace,

Robert K
1991 535i

[genphreak]

I also have a 1991 535i with about 155K miles on it. When I revamped the stereo system in my car, I just took the stock amp out and ran the stock stereo cable to my new amp. My understanding was that the factory head unit put out line level signals, which I ran to the line level inputs on my new amp. The hardest part was just deciphering which wire carried which signal (e.i. which was front, left positive, etc. Many are high level outputs, thought the stock wiring can be used for both- so long as you have low level gear at each end. :) Nick

[onZedge]

OK. I was trying to use a Pioneer head unit, from a '88 M3 I broke long ago, to replace the fried CM5901 factory head unit. I tried many combinations. With and without PAC-OEM2. Could not get it to work properly. I finally figured out how to, and was going to, surgically bypass the amp at the circuit board level when I discovered all four of the input coupling capacitors were swollen. So I re-checked the Pioneer head unit and found that its' amp was fried too. Dunno what fried what.
SO. I repaired the factory amp/crossover to new condition by replacing the bad capacitors and stuck it back in the trunk. This time I tried an old Kenwood cassette receiver that had a fairly low power amplifier. 4WRMS X 2 to be exact. Works perfectly.
WHAT I LEARNED: This particular amp/crossover has some sort of active equalizer circuitry. I could have bypassed the amp by isolating the crossover from the rest of the circuitry on the board, but this would have required electronic surgery, trace cutting and jumper wires. I'm not sure if it would have sounded any good without that active equalizer circuitry anyway, but I'm sure it would have worked if I had tried it. I can see now that any upgrade will be a major undertaking but it works good enough for now. Works really well, actually!