Can anyone confirm with any certainly whether the E36 stock audio system has a common ground system or a floating ground?

Thanks

Each speaker has its own negative and positive. It is not common.

So is it considered "balanced"?

Where are you getting these terms from?

An alternate version of the question: what are you actually asking?

It is my recollection (a few years now since I was messing with it) that the "high level" signals from the head unit are capacitively coupled; i.e. none of the inputs are grounded. In that sense, you could describe the inputs as "balanced"; the actual input signal is the difference between the signals presented to each of the two inputs.

You can drive the amp single-ended by grounding one input and applying a signal to the other, but with a headphone-level signal (e.g. an iPod) the output level is poor. I may have posted a photo of the point at which I tapped the input circuit to inject a 'phone/line level input at some point - search is your friend (I am too lazy to check).

If you are referring to the output stage; again my recollection may be incorrect but I believe the amplifier output is configured as a bridge ("differential" or "balanced"), i.e. both speaker wires are actively driven.

= Mike

Well, I'm fighting a battle with alternator whine.

So rather than try a hundred different thing, I thought I'd pick up an amp that has balanced inputs. I've read that balanced inputs are much superior for rejecting noise.

Hence, my questions...

So.. you currently have the stock system, with alternator whine? You've got some issues then.

If you have an aftermarket setup.. try some decent RCA's.

not quite stock...

only stock piece remaining is the stock head unit.

I replaced the RCA's with some spiral wound monster cables.

Grounded directly to the battery.

still whining...

Where do you have them run?

Just a short run...

RCA's go from the LOC that is connected to the where the stock amp connector used to be.

It is my recollection (a few years now since I was messing with it) that the "high level" signals from the head unit are capacitively coupled; i.e. none of the inputs are grounded. In that sense, you could describe the inputs as "balanced"; the actual input signal is the difference between the signals presented to each of the two inputs.

You can drive the amp single-ended by grounding one input and applying a signal to the other, but with a headphone-level signal (e.g. an iPod) the output level is poor. I may have posted a photo of the point at which I tapped the input circuit to inject a 'phone/line level input at some point - search is your friend (I am too lazy to check).



please do try and find the picture your talking about. i think i may have a floating ground that i'm missing thats causing my sub-channel on my amp not to work. if you could find that pic or a link that'd be awesome.

back OT.

Just a short run...

RCA's go from the LOC that is connected to the where the stock amp connector used to be.

how did you connect your loc (line out converter?) to your stock head unit? i took the output wires from the stock head unit to the stock amp and spliced in rca connectors. i have never had any whine, feedback or amp popping for the 6 years it been connected like that. i've read that because of the low voltage coming out of the head it doesn't warrant the need for a high to low level converter.

entropy,

I've read countless threads where individuals just get berated for even suggesting such a thing.

What amp are you using? Does your amp have a selectable high/low level switch? Some amps will accept a high level signal via RCA's.

But it sure would be nice to forego the LOC's.

i'm running an a/d/s/ ph30.2 through two inputs (6 allowable) off the stock head. each pair of channels has its' own adjustable (100mv 8vrms) input. i based all this on the first post in this (http://www.unofficialbmw.com/all/stereo/all_audio_tips.html) thread. it worked for me then and continues to do so. if i did have to use a conveter i would have opted for something nice, not a radioshack special. i used to use this (http://www.linkmeup.com/prod03.htm) back in the day.

http://www.linkmeup.com/images/pl2.gif


entropy,

I've read countless threads where individuals just get berated for even suggesting such a thing.



yeah ain't the internet great

What the heck, I'll give it a try and report back...

Thanks for the input.

what amp do you have anyway?

by the way, the above is something that work(ed)(s) for me. i don't know the negative effects of doing this and it not working. either way, proceed with caution in anything you do.

I have an Arc Audio 4050xxk. It can handle an input between 250mw to 2.5V.

I have an Arc Audio 4050xxk. It can handle an input between 250mw to 2.5V.

Your amp does not accept balanced inputs. You need to keep your LOC.

Matthew

It looks like the a/d/s/ ph30.2 can accept signals from 100mv to 8V...As well as accept a balanced signal.

ok, the talk of "balanced" has cornfused me. but, i think i get it now. i think because your amp, unlike mine, does not have a readily available input other than preamp (rca) connects (mine also has a mini-din connection). because of this the amp is not able to receive such a signal before being stepped down via a converter.??? here's a quote from my amp manual.

"Because of the high impedance of the a/d/s/ input stage, the factory radio drives an easy load. This ensures lower distortion levels than if it was driving speakers or a Line Output Converter accessory. As a result, a high quality factory installed radio can deliver high quality sound which is nearly as good as the sound from a high-end aftermarket source unit. The speaker outputs of the factory radio are simply connected to a mini-DIN adapter as shown below. From this point on, the signal can be treated exactly as you would a preamp-level signal, except that the input level controls on the PowerPlate will be set to a lower than usual level when you make your final adjustments."

so yeah, you need to continue to use your converter with that amp. which one are you using? i assume a higher end one.

Somebody correct me it I'm wrong, but I believe 'balanced" refers to sending a signal on the postive and the opposite phase signal on the negative.

I'm using a Navone NE-777 LOC.

Somebody correct me it I'm wrong, but I believe 'balanced" refers to sending a signal on the postive and the opposite phase signal on the negative.

I'm using a Navone NE-777 LOC.


i try and not use LOC's...but if i do, i LOVE the Navone units.

Somebody correct me it I'm wrong, but I believe 'balanced" refers to sending a signal on the postive and the opposite phase signal on the negative.

I'm using a Navone NE-777 LOC.

You are essentially correct. The key point is that neither signal is at ground potential ("floating").

There should be no issues with using a quality LOC, such as anything made by Navone (or the Monster LOCs designed by Navone). In most cases, their devices are better than the amplifier's internal circuitry and cause no degradation.

Matthew

i'm running an a/d/s/ ph30.2 through two inputs (6 allowable) off the stock head. each pair of channels has its' own adjustable (100mv 8vrms) input. i based all this on the first post in this (http://www.unofficialbmw.com/all/stereo/all_audio_tips.html) thread. it worked for me then and continues to do so.



Hey entropy, did you physically connect the outside (shield) of the rca's to the headunit chassis or to the common ground wire of the headunit? Should be the same, right? I did this with the common ground wire, but I am left with a high pitched tone (engine off) originating from my headunit running to my jl amp. I'm doubting the quality of my rca's, tho, so I may upgrade those and see if that resolves it.

mreloc,

bear in mind my car is a 95 m3 and there are 4 signal wires from the stock head unit to the stock amp. i took the rear signal wires. (blue w/black, brown w/orange) and (yellow w/black, brown w/orange) and literally spliced each color to an rca connector. positve to center conductor and negative to outer conductor.

:eek:
after re-reading the bob hazelwood article i linked to above i realized i did exactly what he said NOT to do. however, it seems to work for me. if anyone attempts this, don't blame me....this is the internet and you can't believe everything you read.

on another note, i am trying to purchase this (http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=170088718647)

http://i153.photobucket.com/albums/s240/entropy_/30df_1.jpg?t=1174407773


and if i do and retain a factory head unit i will use it and report back differences between my method and and the right method.

however, don't hold your breathe i'm uncertain when i'll get around to it.

kaineilsen, sorry for any confusion i may have caused you.


EDIT: to clear the air. in order for the above connections to be possible your amplifier must support or be able to accept high level inputs. i merely changed the shape of the connection. my high level input were in the form of low level connectors (rca type leads)

Your amp does not accept balanced inputs. You need to keep your LOC.

Alternately, you can just take one (the same side) of each high level pair, connect it to the tip on the RCA, leave the other wire and the ring un-connected.

For amplifiers with local grounds on their inputs (most cheap amps) this will work OK. Be careful about insulating the unused pairs, and be aware that you are engaging in some seriously shonky engineering...

= Mike

Alternately, you can just take one (the same side) of each high level pair, connect it to the tip on the RCA, leave the other wire and the ring un-connected.



You lose the inherent noise suppression of balanced signals if you only use one wire. BMWs employ twisted pairs of signal wires exactly intended for balanced signal transmission, so you would need to install shielded cables if you only use one signal wire, and ground the shield to the chassis or amplifier.

"Shoddy", yet many people do it knowingly or otherwise...

Matthew

exmaxima1, I hope you are on to something that may solve my problem discussed here, since I used cheapo RCA cables: http://forums.bimmerforums.com/forum/showthread.php?t=710366

So, do you prefer to use both wires vs. grounding the shield to the chassis? Or is using good shielded rca's and grounding to chassis a better way to go?

exmaxima1, I hope you are on to something that may solve my problem discussed here, since I used cheapo RCA cables: http://forums.bimmerforums.com/forum/showthread.php?t=710366

So, do you prefer to use both wires vs. grounding the shield to the chassis? Or is using good shielded rca's and grounding to chassis a better way to go?

If your factory HU has balanced outs, which most later BMWs do, then the balanced scheme is definitely the best. It is immune to extraneous noise, and can drive a cable better as well. If your amp does not directly accept balanced signals, then invest in a LOC or new amp. In my car I use an Audio Control EQ (accepts speaker level/balanced inputs) to convert the balanced signal to regular single-ended (RCA) outputs to my regular amplifiers. No noise.

Matthew

So, to reiterate (or, kick a dead horse again) having a cd43 with + and - speaker wires (4 sets) = balanced output, right? My JL a4300 says it accepts balanced inputs (upto 8v), so I guess I will rewire using both + and - speaker wires instead of the ground to chassis way. (Crossing my fingers that this will work!)
Thanks again

So, to reiterate (or, kick a dead horse again) having a cd43 with + and - speaker wires (4 sets) = balanced output, right? My JL a4300 says it accepts balanced inputs (upto 8v), so I guess I will rewire using both + and - speaker wires instead of the ground to chassis way. (Crossing my fingers that this will work!)
Thanks again

Yes, the speaker wires are balanced, and you can wire them direct to your amplifier.

Good Luck,

Matthew