factory amp bypass (my way - lots of pics)

[BMWDriver]

The diagram Tim shows matches what the PCB says for the harnesses. So it seems though the amp is different, it's the same layout for the cabling.

Pics :
Here's the monster:


Here's the back of the PCB of the harness connection:


As you can kind of see (letters are blurred out of focus) A6 is FRM and so on as per the diagram Tim showed. There are coils, and plenty of capacitors. I wonder that the writings on the coils are a standard thing or just part numbers. So in making a custom PCB, I might be able to re-use a lot of these parts.

EDIT :
Found an invaluable resource : Understanding Electronics Components
There is even an example of a crossover.

[tim eh?]

Yikes! That is different.

OK - like I mentioned I'm not an expert in this, I've soldered patch cords before but this was the first time I've gotten this 'dirty' when it comes to car audio. I was lucky plan 'b' worked... I suggest you should have a plan 'b'... I even had a plan 'c'.

What genphreak suggests about getting an old style amp is your best plan 'a' I think - it's a lot less work doing the bypass in Derek A's pics, your plugs are compatible plus you would have your amp as a backup.

That said, I can help you a bit to identify the components if you want to try a complete gutting like I did. The coil inductors are easy - those are the low pass filters (ie they block high frequencies) so almost without a doubt 'W03' is for the front low speaker, 'W02' for the rear low speaker and 'W01' will be combined with a high pass filter (capacitor) for the front mid (dash).

The capacitors could be difficult. Sometimes they are combined to make a different xover point, so it's not certain you are only looking for 3 of them. There will be one filter for the rear tweeter, one shared between the front mid and tweeter, and one extra for just the front tweeter. It's just they could be in pairs or worse so make sure you follow all the circuitry. Use this diagram and work backwards from the plug.

*- The circuits should trace through the capacitors/coils and meet up at the pin connectors to the amp section. This is the amp output, each row is probably for a separate channel ie LF, RL, LR, RR. In each row of pins there should also be a pair of pins for the head unit output/ amp input and a pair for the speaker ground to the head also. This is normally where you would solder the hu output. It might be easier to work with if you remove the amp section. Follow me?

I fixed both of my rear speakers with glue. The big black rubber rim was partly loose, making bad bass quirks, so I made it entirely loose and glued the thing. Problem solved, no issues.

Interesting and nice fix, so you blew your rear speakers too! What kind of glue did you use?

[tim eh?]

I never had the factory fader... ? Where is it located?

Actually I do have the rear window antenna and it works very well with my old skool jvc... eventually I'll go looking for the antenna amp and play with that some .

Sorry - still curious - I don't quite get... how are your speaker grounds set up?

And I don't have an ipod but I do have a line in anyway. Actually I can't stand most mp3s even in a car - cassette sounds better even.

[BMWDriver]

Automotive Goop. That's the glue I used. The P.O. had blown them a bit. But I got it with right rear channel problems too, where it would come on and off. The HU was to blame, so I got me a new one three years ago.

I've taken out the inductors, mapped out where they go, and I've come to a diagram similar to yours, except for the RR+ and FR+. So thanks for the missing clue. On the amp, all feeds go right through some chips and capacitors like there's no tomorrow. Of course, it's for signal processing. Not much use figuring that out.

I've measured the inductors :
W01: 0.4 Ohm
W02: 0.7-0.9 Ohm (one gives 0.7 and the other 0.9)
W03: 1.0 Ohm (one gives 0.9)

Capacitors linked to the inductor coils go as :
22µF 16V
33µF 25V

Diagram :


Now I have a bit of shopping to do

[genphreak]

Oh sorry, I wasn't clear. I run the factory wiring from the crossover to the speakers; made the job a snap... factory fader is beside the steering column on my 88 535. It is a high level fader- and work on the outputs of the radio before the signal is set down the back to the booster amp.

Since I laid low level wiring, to do this from my new head unit, there was no need for using any of that.

Noone wants to use high level outputs of course, but I beleive you can use that same twisted pair instead. But if you have the fader, you'd want to bypass that. With low level signal, common ground is no problem (but chassis is), however I don't think the stock twisted pair is common ground after the fader. Check the pin-outs on the booster amp plug to see.

Nick

[tim eh?]

Nice work! Where did you find that diagram?

Interesting your amp uses the same capacitors for all the tweeters and mine uses different ones for front and back... don't have the values handy...

On the amp, all feeds go right through some chips and capacitors like there's no tomorrow. Of course, it's for signal processing. Not much use figuring that out.

Yes that might take some time and you are bypassing that stuff anyway.

.... and I've come to a diagram similar to yours, except for the RR+ and FR+.

errr... FR is same as FL and RR is same as RL...

[BMWDriver]

I made that diagram by looking at the PCB. Had to take out a few items to get it right. I made many passes in order to make absolutely sure it is right. Took me some hours.

I meant I had no clue where all the positives came in at first. Your diagram clued me in on it.

I'm a bit puzzled on the negatives though. I'll get back on this later. Enough for today.

[tim eh?]

I made that diagram by looking at the PCB. Had to take out a few items to get it right. I made many passes in order to make absolutely sure it is right. Took me some hours.

I meant I had no clue where all the positives came in at first. Your diagram clued me in on it.

I'm a bit puzzled on the negatives though. I'll get back on this later. Enough for today.

oh ok haha so you figured out the symmetry already my bad. Nice diag "...many other things..." no kidding eh?

The speaker grounds don't even have to run through the amp although they do run through it in the factory setup. Each corner speaker group shares a speaker ground that should go straight back to the head unit. In the factory setup there are only two shared grounds that go back to the head, each side is spliced together somewhere inside the factory amp (bentley ewd-206). I tried using the shared grounds but the front/rear fading got all screwed up. I would suggest not even bothering trying that- instead I would suggest you pop the 4 speaker grounds out of the amp plug and run new speaker grounds straight to the head. A slight inconvenience but on the sunny side you can run an rca for your future sub at the same time . You can borrow my 'shogun extractor' if you want, they are easy to make tho.

A note about speaker grounds/negatives as some people might not be aware-

They are not real grounds in the sense that you can ground them to the chassis. They work the same way, but only in relationship to the speaker+ feeds not a regular DC+ current. They need to complete the speaker signal circuit back to its origin.

Just about there, man - soon your ears will thank you - Keep at it Philippe!

***- check it out - so it wasn't the dog farting in the back!

goop you say huh?

[BMWDriver]

Yup, that's exactly it. I first loosed all of that rim, and then glued it back on with the goop. Worked out perfect.

What really stumps me though, is that there are SIX negatives listed on the PCB, contrary to the diagram you posted up. On it is printed what every pin is for. This is what it says for the negatives:

B2 FL-
B3 RL-
B4 FR-
B10 FL-
A5 FR-
A10 RR-

That's right, two sets of front negatives. Which makes sense because the tweeters are not on the same circuit as the kicks, unlike the back where everything is on the same circuit. But it doesn't specify which is the tweets or kicks.

So nothing's going back to the front by the amp. Well, that's why these wires have colors. I'll have to take out the tweeters to find that out.

My head unit is already wired in, so I don't see why I should bother with runing wire back up there. It already worked with the amp hooked in... which means it's already a closed circuit (the speaker negatives are coming in already to the HU like you said).

So we got a B+ and a couple of grounds free from the amp. I wonder how that could be used... like for a woofer amp maybe?

So far my expenses run up to less than 30$, and that includes some new tools, which is an investment. Addison Elecrtonic have good knowledgeable staff. They are quite popular I see, of late. And they are getting more square feet.

And speaking of woofers, they have a deal up right now for a 12" with an amp for 100$, but no box. I think it's a Pionner with a 100W amp, I forget. They have tons of speakers my friend.

However, that woofer project will have to wait as far as I'm concerned.

[tim eh?]

You are mistaken about the tweeters being on a different circuit. Each corner shares a single ground. These are the plugs B2, B3, A5 and A10. See bentley ewd 206.

B4 and B10 are the L and R grounds attached to the head unit. You can try to splice into these and you'll get sound but your fader won't work. With this setup it won't work unless you run 4 new separate speaker grounds. I tried splicing them already, you can see the little splice cables I made at the bottom of this photo.

So we got a B+ and a couple of grounds free from the amp. I wonder how that could be used... like for a woofer amp maybe?

it's even on a 30A fuse already. it's either for an amp or for the fridge, haven't decided yet...whichever goes in first I guess.