CD43 Head Unit & Audio Amp Fundamentals - A Primer [LONG]

[dirtysix]

Do you ground it at both ends?
IE; headunit and amp.

[StereoInstaller1]

Luke,

Thanks for that, but to insist again, should I wire the "+" and "-" from the deck on the RCA cable to the Amp, or only the "+" to the RCA and ground the "-" on the unit ground or car ground ?

My idea was to solder each CD43 speaker outputs + and - to an RCA plug and then connect the amp via a standard RCA cable. No grounding whatsoever. I dont need a LOC right ?

please enlighten me.

Cheers Pierre

That one! Center pin is speaker positive, outer shield is chassis ground, DO NOT use the speaker negative.

[pegase747]

And Pierre, you have a solid grip on it. Feed these RCAs into any decent amp, you will be fine. RCA plugs can be bought at Radio Shack, they have some decent ones.

Luke,

Thanks for that, but to insist again, should I wire the "+" and "-" from the deck on the RCA cable to the Amp, or only the "+" to the RCA and ground the "-" on the unit ground or car ground ?

My idea was to solder each CD43 speaker outputs + and - to an RCA plug and then connect the amp via a standard RCA cable. No grounding whatsoever. I dont need a LOC right ?

please enlighten me.

Cheers Pierre

[StereoInstaller1]

Lemme say this clearly with great emphasis: an LC6 is a waste of time on this deck.

The 7 I can see as it does much more, but even that is pointless. AUX in can be done a lot better than that.

I have done several installs using these decks, never have I had ANY noise issue, and the noise floor of the system is stunningly low too, because the gains are generally near the bottom of the range.

The 6XS is of course a completely different animal, as it is a crossover, not just an adapter.

If you can afford the money to get an LC6, get better amps instead. Aim for "/ series" JLs at a minimum, but aim for Zapco, or better still, ARC Audio.

And Pierre, you have a solid grip on it. Feed these RCAs into any decent amp, you will be fine. RCA plugs can be bought at Radio Shack, they have some decent ones.

[pegase747]

Pierre, you will use the speaker + to the center pin of the RCA, and then use chassis ground on the outer shield.

Do not use the speaker - from the deck at all.

Thanks Luke,

Do I need to do that when only connecting the CD43 straight to my AMP ? I dont plan to use LC6i or 6XS just now...

Please let me know.

Cheers Pierre

[bmwman91]

Yup, that's how you would do it.

[TurboFox93]

Again I apologize for the hardheadedness; so tell me if I understand this correctly:

So using the LC6i, you would route both CHx+ & CHx- from the HU to the trunk and into the LC6i. The LC6i would help "clean" up the signal from any noise that was picked from the HU to the trunk. You would then just use regular RCA connectors between the LC6i,6xs, and amplifier of choice?

[bmwman91]

The advantage of the LC6i would be in signal noise reduction. If you run the wires from the HU to the trunk there is a lot of room to pick up noise. If you just run one of the outputs to the 6XS, the noise stays with the signal & goes all the way through the amplification system & to the speakers. The LC6i can accept a differential type input (inputs are not ground-referenced like they are in the 6XS). If the two lines (CHx+ & CHx-) are very close to each other, preferably twisted together, then the same noise will be present in both lines and in the same polarity. Remember that the important part of a differential signal is not the value of one or the other, but the difference. Basically, the noise is canceled out since it is the same in both lines.

Then you can put the LC6i 3" from the 6XS & only have that much ground-referenced / unbalanced signal line in the system. If I have noise issues I will add an LC6i. However, I don't really foresee that happening.

You can get DIY RCA plugs all over the place. Some are crimp type, some are solder type and some are both.

[TurboFox93]

So at what point or setup would it be beneficial to run AudioControl's LC6i? Is there an advantage to running the outputs from the CD43 into this prior sending the signal onto the 6xs?

If not, do they sell "pig tail" type RCA cables that allow you to neatly splice the + speaker output onto the RCA cable? Where nd what would you ground the shield to ( i.e near the HU or closer to the 6xs; ground to clean bare metal or a negative lead from the battery.) I am a total newb when it comes to doing this and I appreciate the constructive feedback.

[StereoInstaller1]

Pierre, you will use the speaker + to the center pin of the RCA, and then use chassis ground on the outer shield.

Do not use the speaker - from the deck at all.

Audiocontrol 6XS is an amazing crossover/signal processor. It has up to 6 channels of input and several output options. It has a subwoofer controller, too.

[pegase747]

Hello all,

I will also try to make an install with a CD43 soon on my Touring, and I was wondering one thing..
First please note that I am French and my technical english may not be understandable to you native speakers...

For the details I will use the following :
HU : BMW-Blaupunkt CD43
AMP : Alpine PMX-F640, not avail in US, but basically 4-channel amp, has Speaker wires input, RCA input & output , can give 4x50Wrms
Front Speaker : Pioneer TS-C520PRS- 2x30Wrms, 2x150W max.
SUB & SUB Amp : not defined yet
Processor/Eq : Not defined yet

So BMWMAN91, when it come to wire RCA plugs from the CD43 Output ? Shall I :

1/ weld the Speaker out "+" on the RCA plug center core and the "-" on the outer core ?

2/ Either weld the Speaker out "+" on the RCA plug center core OR the "-" on the outer core ? The unused one to the car ground ?

3/ Use a line driver with speaker wires input and RCA output ?

4/ Use a Linear output Converter with speaker wires input and RCA output ?

Also I see you use the 6XS, why this choice ? care to elaborate on the 6XS ??

Your help much appreciated.

Cheer Pierre

[harv]

Nice wright up.

Thanks for the great info.

John

[onaquest]

Very thorough bmwman91. Thanks!

[bmwman91]

Dude! Brilliant! Finally, analysis of the famed CD43.

Did you, by chance, load this using the little hack I stole from ADS, Fosgate, Orion, PPI and others? We all seem to think that using chassis ground as the "negative" drops output voltage...I have always wanted to know way more of the truth of that...why even stock amped E32/34/36 systems generally sound SO much better when you use chassis ground as the input ground for the amp?

What was the "hack" recommending a chassis ground connection to...the amp's power ground (pin 15), or the 4 "negative" output lines? I would definitely recommend against connecting the "-" outputs to ground because they are putting out a fully powered signal. Connecting those to ground would be a short circuit.

In E32/34/36 cars, how is the head unit grounded stock, and what do you typically change to improve it?

Good write up. I was hoping that someone could shed some light on these decks.

Are there any audio differences between the CD43 and the C43?

I wanted a tape deck in mine to look even more retro but I'll be using a Phatbox mp3 player for my music.

If the C43 was produced at the same time as the CD43, then it probably has the same amplifier ICs. Of the few decks I have taken apart over the years, they all seem to use STMicro am ICs, and even looking at what is available on DigiKey I would estimate that there are no more than 5 different ones in use today lol.

[Jean]

Nice job!