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Thread: Using C43/CD43 with aftermarket amp questions (preamp output/input???)

  1. #1
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    Using C43/CD43 with aftermarket amp questions (preamp output/input???)

    Hi everyone,

    I know you guys probably read the title and all came here to tell me to use the search function but I can't find anything related to my question!

    I am planning on using my C43 (probably has similar output stages to the "famed" CD43) with aftermarket amplifiers. I am planning on using a line-out converter in order to step down the output voltage until it reads around 4 volts with a voltmeter at nearly max. volume. I've come across some evidence on the CD43 that suggests that its output voltage peaks at around 5 volts in the following link. In this link is a series of linked photos which shows the output of the CD43 on an oscilloscope, and its output voltage as you turn the volume up. You can see that it starts clipping at just shy of 6 volts. (You can see in the photos referenced in the link where it says "Delta Y(1) = 11.4375 V" if you divide this by (2) that is your net positive or negative output voltage I assume)

    http://www.r3vlimited.com/board/arch...?t-170952.html

    My question to you guys is this: will increasing the resistance on the output via an adjustable line-out converter allow me to have a more full-range motion of the volume knob without the onset of clipping? Or will you just end up with clipping at a lower output voltage?

    Thanks!

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    C43 is absolute garbage sound and output compared to the CD43.

    The CD43 is not a C43 + CD transport. It is, sonically, leaps and bounds better.
    Tenured Automotive Service Professional - Avid BMW Enthusiast

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    Quote Originally Posted by Stück View Post
    C43 is absolute garbage sound and output compared to the CD43.

    The CD43 is not a C43 + CD transport. It is, sonically, leaps and bounds better.
    This still doesn't answer my question. I brought up that assumption merely to use the evidence that I found to stage my question. So lets say that the C43 starts clipping at 4V instead of 6V... Whatever. Same thing still applies. This is more a question of physics than anything. Does dropping voltage via and adjustable line out converter reduce the extent of clipping at "max" volume?

  4. #4
    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Do not use a LOC, unless it is an active device such as an Audiocontrol. Well, actually, let me rephrase that: don't waste your money on an LOC, it is detrimental to the interface between your deck and amp. Yes, even the Navonne, there is no good way to run your music through a transformer and a bunch of resistors and expect decent performance afterwards.

    It has been conclusively proven that the BMW decks are single ended, thus connecting to an amplifier is very easy: simply solder on RCAs.

    The trick is this: solder the positive speaker wire to the center pin and use chassis ground on the outer shield. It is the best way to interface that deck to an aftermarket amplifier...and in fact, that is exactly what happens in the stock amp.

    This simple trick is the best sound quality you will get out of that overpriced pile of deck, but beware, any $100 walmart deck will put it to shame.

    Yes, I know, I hear people all the time saying how they love the look, so I won't argue the point...but just be aware all other decks perform better.

    Best of luck!
    Luke


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    Quote Originally Posted by M20E34 View Post
    Do not use a LOC, unless it is an active device such as an Audiocontrol. Well, actually, let me rephrase that: don't waste your money on an LOC, it is detrimental to the interface between your deck and amp. Yes, even the Navonne, there is no good way to run your music through a transformer and a bunch of resistors and expect decent performance afterwards.

    It has been conclusively proven that the BMW decks are single ended, thus connecting to an amplifier is very easy: simply solder on RCAs.

    The trick is this: solder the positive speaker wire to the center pin and use chassis ground on the outer shield. It is the best way to interface that deck to an aftermarket amplifier...and in fact, that is exactly what happens in the stock amp.

    This simple trick is the best sound quality you will get out of that overpriced pile of deck, but beware, any $100 walmart deck will put it to shame.

    Yes, I know, I hear people all the time saying how they love the look, so I won't argue the point...but just be aware all other decks perform better.

    Best of luck!
    Luke


    Thanks for the input! I agree, even the CD43 is a huge heap, and at $200+ there's no way I'm getting one... I just like the factory look and the lack of attention it gets from people who might want to break in.

    I just don't want to damage my input stages on my amp by sending them a high volt clipped signal, but if you say that this can be done successfully by just tapping RCA's then I'm in! And you know for sure that using a "common ground" on the RCA's works?

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Quote Originally Posted by briceman View Post
    Thanks for the input! I agree, even the CD43 is a huge heap, and at $200+ there's no way I'm getting one... I just like the factory look and the lack of attention it gets from people who might want to break in.

    I just don't want to damage my input stages on my amp by sending them a high volt clipped signal, but if you say that this can be done successfully by just tapping RCA's then I'm in! And you know for sure that using a "common ground" on the RCA's works?
    I have done that trick on well over 50 BMWs and I have only had an issue once or twice.

    Expect to have your gains almost all the way down though!

    Luke


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    Quote Originally Posted by M20E34 View Post
    I have done that trick on well over 50 BMWs and I have only had an issue once or twice.

    Expect to have your gains almost all the way down though!

    Luke
    Haha alright. Well I'm glad to hear you've had good success with this, that makes me feel a lot better about this. Thanks!

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    Quote Originally Posted by M20E34 View Post
    The trick is this: solder the positive speaker wire to the center pin and use chassis ground on the outer shield. It is the best way to interface that deck to an aftermarket amplifier...and in fact, that is exactly what happens in the stock amp.

    Luke
    Luke - are you saying to use a direct chassis ground wire to the RCA's outer terminal instead of the negative speaker wire coming from the deck??

    How is this different than using the negative speaker wire?
    Last edited by Eric98Sedan; 04-14-2014 at 01:51 PM.

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Quote Originally Posted by Eric98Sedan View Post
    Luke - are you saying to use a direct chassis ground wire to the RCA's outer terminal instead of the negative speaker wire coming from the deck??

    How is this different than using the negative speaker wire?
    Yessir, I am saying exactly that.

    Let me explain: Modern decks (aftermarket and OE) all use a derivative of the same little POS amplifier chip. That chip has an output of 12 watts RMS per channel (4 channels, 48 W RMS total) when you compare the negative and positive. If you read the manual or install instructions, it says clearly NOT to use chassis ground anywhere on the speakers wiring, do not share a ground, do not use common ground, etc. Basically, it says 2 wires per speaker under all circumstance. The reason for that is simple: these outputs are called "BTL" or "Bridge Tied Load" and they will blow up in a hurry if you try to use them in a common ground system incorrectly.

    This is, BTW, where all the confusion about BMW decks being "balanced differential output" comes from, and has been proven beyond doubt that they are NOT "balanced" output. That discussion was beat to death elsewhere on this forum, I would be happy to link if needed. That nonsense was started by none other than Bob Hazelwood of A/D/S/, who most certainly should have known better, even in 1988, he is a brilliant guy. Balanced requires 3 signal wires per channel, BMW uses 2. In fact, I believe they only use 1, but thats a whole 'nother story. IMO (meaning I have zero proof) BMW uses chassis ground inside their amps, so the same deck can be 12WX4 for use in euro base model cars that don't have an amp can be used in their "Top HiFi" systems that do have an amplifier. It does fit logical parameters to do so and we all know BMW is always logical, even if we don't understand their methodology.

    So, back to BTL design: in a BTL output, both the speaker negative and positive are "above ground", allowing roughly triple the power of a "common ground" output. For us old guys, we all remember back in the 80's when decks all became "high power", this is how it happened.

    However, if you compare the positive to chassis ground, that same chip only makes 4 watts instead of 12. Runs cooler and with much less distortion, too. Basically, without that second "leg" of the chip amp being used, it goes into old school "common ground" mode.

    You can test this very easily BTW, with nothing but any working deck and a normal speaker: connect it using the speaker negative and positive, listen to it, and then change the speaker negative to chassis ground (disconnect the negative!) and you will notice a huge drop in volume...but an actual increase in clarity, a reduction in hiss and noise and it will run cooler by 50% or more. Adjust the deck to play at the same volume levels, of course, but you will see immediately what I am talking about. It is quite shocking, in fact.

    So, here is the trick: if you do as I described, use chassis ground as the signal reference, you will find several benefits. First, by dropping voltages, you get a huge reduction in background noise. Second, you get an increase in clarity. Third, you are less in danger of overloading your amplifiers input stage, so it plays much cleaner and clearer. Fourth, you won't need an LOC, which are the absolute worst sound quality devices in all of car audio. They use resistors and transformers to reduce the input levels, both of which are atrocious when inserted into the signal path. Generally, this method also eliminates most noise, but ground loops can still happen.

    Now, let me state emphatically: this does not work on all decks, nor all amps. Some are such garbage that even the lower levels of output are still too much for the input stage and are still overdriven by the signal. Most any modern amp is just fine, you may have to dig up an old "Rockwood" or "L.A. Sound" amp to find one incapable of handling the input, even most taiwan amps of today are just fine with it. Same with decks, but since we are presumably discussing only OE BMW decks, I won't go into that.

    Hope that clarifies things and thank you for your question!

    Luke Fisher
    German Audio Specialties


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    Thank you!

    Thank you for the very concise "yes, that is what you should do" as well as the technical explanation of why. I've searched for hours and hours and simply could not find this simple recommendation of how to hook RCA ends into the factory HU/Harness.

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    So I hooked it all up, amp has power, but no sound is coming out! I hooked up the middle terminal of the RCA's to the positive radio outputs and then hooked up the outer shell of the RCA's to ground. I tied all of the RCA grounds together and put them on the same bolt in the trunk. I also turned the volume up and down and then after doing that I played with the gains on the amp and nothing happened.

    Am I missing something?

  12. #12
    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    An easy test is this: grab a phone, walkman, whatever, and get an adapter that goes from 3.5mm mini plug (headphone plug) to RCAs.

    Plug the phone in, turn the stereo on to turn the amp on, and see if you have audio.

    If you have audio using that ipod as a source, then you know its all working as it should.

    Then we got to look at other stuff, but start with that simple test.

    Luke


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    Hmmm just tried it and no-go. At least there's hope I hooked up my RCA's right! I switched the iPod around to front and rear channels (the rear channels I actually hooked directly up to the amp with new wire instead of recycling the factory wiring) and still no sound. Played around with the gains and everything. One thing I did notice is that the power LED on the amp is flickering.. Maybe it's switching on and off? I hooked the "remote" wire to the white wire coming out of the factory harness (Pin 2 as referenced by pinouts). I might try to hook up the factory amp's power wire to the remote and see where that gets me.

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Quote Originally Posted by briceman View Post
    Hmmm just tried it and no-go. At least there's hope I hooked up my RCA's right! I switched the iPod around to front and rear channels (the rear channels I actually hooked directly up to the amp with new wire instead of recycling the factory wiring) and still no sound. Played around with the gains and everything. One thing I did notice is that the power LED on the amp is flickering.. Maybe it's switching on and off? I hooked the "remote" wire to the white wire coming out of the factory harness (Pin 2 as referenced by pinouts). I might try to hook up the factory amp's power wire to the remote and see where that gets me.
    Oh man...yeah, triple check that.

    Do you have a test light? If not, go get one at Walmart, they are $5. Test your power wires using a testlight, a meter won't show a load.

    Like you said, at least you know it isn't necessarily the deck!


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    Quote Originally Posted by M20E34 View Post
    Oh man...yeah, triple check that.

    Do you have a test light? If not, go get one at Walmart, they are $5. Test your power wires using a testlight, a meter won't show a load.

    Like you said, at least you know it isn't necessarily the deck!
    Got it! It was a bad grounding location.. What I though was a connection with quite a few threads was actually just a sheet metal clip (where the stock amp was mounted).

    Everything sounds great! I haven't tuned the gains yet, but so far so good (they're right around 4 volts right now, on an Excelon XR400-4 amp driving Polk MM's). Now I just need to get that sub box finished and find some screws for my 6x9 adapters. Heaven forbid that you should be able to re-use the stock screws!

    Thanks for all your help, I wouldn't have gotten this thing hooked up right otherwise

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Thanks, glad to be of assistance.

    What are you building for a box?


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    I'm going fiberglass in the rear left corner of the trunk, it's a sealed box that will be about 0.6 ft^3 when it's done and house a 10" alpine type S (my last car had a diamond d310 driven by a boston gta1105 with only 250rms in a ported box and it was satisfactory)

    So far my setup is:

    Kenwood Excelon xr400-4
    Kenwood Excelon xr600-1
    Polk Audio MM5251 components
    Polk Audio MM691
    Alpine SWS10D4

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Ah gotcha, one of those corner boxes. Post pics and GLWP!

    Luke


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    Okay, so the story continues... Got everything hooked up and working, but I have no real bass coming from the speakers compared to the stock hk 6x9's. I turned the HPF off even and no change.. This is especially strange because usually when you turn off the high pass filter your speakers start to sound like garbage pretty quick don't they?

    I also tried hooking up the ol' iPod directly to the amp and it does the same thing... Hmmm. It does take care of the engine whine I have going on though.. (Speaking of which, how do you take care of ground loops with this setup?!)

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    No, your speakers should sound just fine like this, especially using an Ipod as an input.

    What do you have going on for crossovers, speakers and amplifiers?


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    Turn the balance control from left to right. If the bass comes back everywhere but center you have wired one speaker out of phase. Check your signal and speaker wiring.

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    I think you guys are spot on, except rather than having my speakers wired out of phase, I think there was some cancellation going on elsewhere... I unplugged the ground for the RCA all-together and there was still music coming from the upper range, although no bass at all. When moving the balance to center, the sound was weakened, and when only having the balance on one side, the sound was fuller, but strangely enough, still coming from all speakers. I thought this was odd, so I tried grounding the RCA's in a bunch of different locations (I also had a pretty atrocious ground loop going on so I went on a mission trying to match the ground potential of everything audio-related, even going so far as to ground the RCA's to the head unit itself, and no luck). After getting pretty frustrated, I just hooked the RCA's up directly to the negative speaker wire coming from the head unit, and ground loop was eliminated and the balance/fader work perfectly. Sound quality seems decent, although I think it was better before like you said (minus the ground loop and balance/fader not working quite right).

    I'm stumped, but at least for the mean time it's working okay.

    As for bass replication, I've listened to it more, and the CD I was testing it on has a lot of music that was resonant on the frequencies favored by the HK 6x9's. I played some music that sounded like garbage on the HK system and it came to life on the new setup so maybe these things just aren't quite as responsive at sub-50 Hz as the HK's are.. but MAN the system is LOUD with 100+RMS watts/channel.. Can't wait to get the sub going!

    Speaking of which, 12vElectronics, did I see somewhere that you have matching gray speaker carpet for the E36?? I will be needing some soon.

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    Just imagine how much easier it would have been by using an LOC

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    Stereoinstaller1 is offline Senior Member Supporting Vendor
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    Which of course, has absolutely nothing to do with it not performing using an Ipod...and if you can't make it sound good with an ipod, you need to figure out what is going on with the amplification and speaker side of things, then you can worry about the input.
    Last edited by Stereoinstaller1; 04-29-2014 at 11:45 AM.


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  25. #25
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    Hmmm yeah I had temporarily forgotten I had tried that.. It sounds extremely good, the response drops off pretty quick below 70 ish Hz on the 6x9's, although I'm beginning to think that's just the way they're designed since they're meant to be run with a full system.. Everything is hooked up right and I took a lot of time and many trips to the hardware store to ensure everything was done properly. The 6x9's are hooked directly to the amp.

    I'm hopefully going to get my sub running soon, so I'll hook it up to my 4ch amp and see if the lower frequencies do exist on my signal.. If not then the amp is going back to crutchfield

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