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      05-31-2011, 05:06 PM   #23
liliceman13300
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Did you try hooking a different device to the rcas? Something like an ipod or mp3 player?

What input do you have set on the head unit? Like I said before the aux jack is noisy and can produce static based on the device or if the cord is plugged into the jack but no device.
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what are u doing on these forums? you dont even drive a bmw or a respected car so i suggest you take your opinions to another forum. Thank you
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      05-31-2011, 10:20 PM   #24
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Originally Posted by VP Electricity View Post
I can't control what you have heard and not heard. But an unloaded, or unterminated RCA input, is an antenna for EMI.

I will quote a paper by Davind Navone and Richard Clarke of Autosound 2000 on troubleshooting noise. (I will fall back on citing an "authority"...)
You realize the quote you posted confirms what I was saying?
The first line says to disconnect the rcas from the amp
If you do that and the hiss goes away, then the hiss was being generated upstream of the amp. If the hiss remains then, and only then, would you try to short the inputs.
Also keep in mind that you can't just short the inputs of any amp, some amps would need a resistor, to present a load to the input stage, or risk damage to the input stage.
you're saying an RCA input plug would act like an antenna, you don't think a 3-12ft RCA would act as a much better antenna?


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We all live and learn.
Guess that applies to both of us
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      05-31-2011, 11:56 PM   #25
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Quote:
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You realize the quote you posted confirms what I was saying?
No, I don't, because no, it doesn't. I'm not going to debate you, Jerry. It has nothing to do with me or you - that's how RCAs work. If you UNPLUG the RCA and leave it open, it can pick up noise. Read it, learn it, live it.

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you're saying an RCA input plug would act like an antenna, you don't think a 3-12ft RCA would act as a much better antenna?
If it were open at the other end, sure. If it's plugged into a device with a properly designed output stage, no, I don't.

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Guess that applies to both of us
Yes, it does, I learn all the time, which means I've been wrong a lot - but all I'm learning from this conversation is that you're arguing with me a lot more than you're researching the actual problem. Why don't you stop arguing and actually look into it by Googling "RCA shorting plugs noise troubleshooting"? I think it would be better for everyone, seriously.
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      06-01-2011, 12:18 AM   #26
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Quote:
Originally Posted by liliceman13300 View Post
Did you try hooking a different device to the rcas? Something like an ipod or mp3 player?

What input do you have set on the head unit? Like I said before the aux jack is noisy and can produce static based on the device or if the cord is plugged into the jack but no device.
It does'nt seem to matter what input I am using.

I tried different rca cables, no success, noise the same. Is this something that happens often when only replacing amp and using a quality amp to vehicle harness? I certaintly did'nt expect to have to deal with noise..
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      06-01-2011, 11:57 AM   #27
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Originally Posted by VP Electricity View Post
No, I don't, because no, it doesn't. I'm not going to debate you, Jerry. It has nothing to do with me or you - that's how RCAs work. If you UNPLUG the RCA and leave it open, it can pick up noise. Read it, learn it, live it.
well i can't argue about what the article you quoted says, because the first line said "Unplug the RCA cables from the amplifier/s"
if you disagree with that, there's not much i can do to help.
the inputs can pick up noise, but you have already decided they will.
i said unplug the rcas from the amp, so the amp is not connected to anything.
if the hiss goes away, then the hiss was coming from the headunit.
if the hiss remains, then you know it's from the amp, at which point shorting the plugs would not be of any benefit, since a properly functioning amp should not pick up noise from it's inputs anyway.
i've used the Xd600/6 and it did not pick up noise nor have a noticable hiss on the outputs

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Yes, it does, I learn all the time, which means I've been wrong a lot - but all I'm learning from this conversation is that you're arguing with me a lot more than you're researching the actual problem. Why don't you stop arguing and actually look into it by Googling "RCA shorting plugs noise troubleshooting"? I think it would be better for everyone, seriously.
i don't need to google something i already know, and have successfully used many times, nor do i need to name drop.
i just had an issue with you trying to over-complicate things
in suggesting an oscilloscope was required to set the gains.
Most JL audio amps i've seen have already done the work for you
and they tell you how many volts should be present at the outputs to achieve max gain. so you don't need to watch the signal on an oscilloscope to make sure it's not clipping.
with troubleshooting any noise, you start removing things one at a time till you find the culprit.
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      06-01-2011, 11:19 PM   #28
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[quote=kmarei;9725567]well i can't argue about what the article you quoted says, because the first line said "Unplug the RCA cables from the amplifier/s"
if you disagree with that, there's not much i can do to help.
the inputs can pick up noise, but you have already decided they will.
i said unplug the rcas from the amp, so the amp is not connected to anything.
if the hiss goes away, then the hiss was coming from the headunit.
if the hiss remains, then you know it's from the amp, at which point shorting the plugs would not be of any benefit, since a properly functioning amp should not pick up noise from it's inputs anyway.
i've used the Xd600/6 and it did not pick up noise nor have a noticable hiss on the outputs


I will try unpluging rca cables and see what happens with the noise. I am at a loss of what else to try...
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      06-01-2011, 11:50 PM   #29
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Quote:
Originally Posted by kmarei View Post
well i can't argue about what the article you quoted says, because the first line said "Unplug the RCA cables from the amplifier/s"
if you disagree with that, there's not much i can do to help.
the inputs can pick up noise, but you have already decided they will.
i said unplug the rcas from the amp, so the amp is not connected to anything.
if the hiss goes away, then the hiss was coming from the headunit.
if the hiss remains, then you know it's from the amp, at which point shorting the plugs would not be of any benefit, since a properly functioning amp should not pick up noise from it's inputs anyway.
i've used the Xd600/6 and it did not pick up noise nor have a noticable hiss on the outputs



i don't need to google something i already know, and have successfully used many times, nor do i need to name drop.
i just had an issue with you trying to over-complicate things
in suggesting an oscilloscope was required to set the gains.
Most JL audio amps i've seen have already done the work for you
and they tell you how many volts should be present at the outputs to achieve max gain. so you don't need to watch the signal on an oscilloscope to make sure it's not clipping.
with troubleshooting any noise, you start removing things one at a time till you find the culprit.
Oh, Jesus Christ. I think JL used to recommend the o-scope method on their site. They now recommend THIS method (apparently many people did not have o-scopes - imagine):

http://mobile.jlaudio.com/support_pages.php?page_id=143

I asked if he used an o-scope. I didn't TELL him to use an o-scope.

I will agree that you can't plug shorting plugs into an amplifier's RCA inputs WITHOUT unplugging the RCA cable from that RCA input FIRST. But in the words of Inigo Montoya, "I don't think that means what you think it means."

To the OP: The technique described for gain setting is intended to make sure you develop max clean power out of your amplifier. Depending on what speakers you have, you may not ever want to develop 75W PC out of your amplifier. What I suggest you do is play the system with a good CD, onme with a decent loudness (no Rickie Lee Jones), turn the volume all the way down on the head unit, then turn it up slowly and count the clicks. The volume controls on the BMW HUs have between 47 and 54 clicks (seems to vary with firmware). The last 5 clicks are usually distorted, so that gives you 43 to 49 clicks of usable volume.

So turn the volume up slowly and count the clicks. If you get to a loudness that is way too high for you to ever use while still in the 20s or low 30s in your click count, your amp gains can be safely lowered without you losing any of the usable volume from the system - and your hiss will improve.

It is possible that the amp is the problem. However, until you try lowering the gains, you don't know.
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      06-02-2011, 01:32 AM   #30
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VP thanks, I have used the 45 click method for usable volume. I don't need quite that much wattage, so I have turned the gains down from the voltage levels as listed in manual. The problem is there is still very noticeable hiss at this level even slightly there with gain at min. Is there anything else that can be done?
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      06-02-2011, 01:41 AM   #31
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If you are hearing hiss with the gains all the way down, that is not consistent with our experience with that amp.

Just out of curiousity, is the treble at flat (0)?

What speakers are you powering?

Is there hiss out of the rears?
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      06-02-2011, 04:34 AM   #32
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Quote:
Originally Posted by VP Electricity View Post
If you are hearing hiss with the gains all the way down, that is not consistent with our experience with that amp.

Just out of curiousity, is the treble at flat (0)?
Yes

What speakers are you powering?
Underseats- SWS-8Xi
In the middle of replacing front doors with MB Quarts RUA213
rears stock

Is there hiss out of the rears?
Yes
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      06-02-2011, 10:29 AM   #33
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ok try this
just to be sure we mean the same thing when we say turn down the gain
unplug all rcas going into amp, turn the gains all the way down (anti-clockwise)
so you have power, ground, and the remote cable going into amp ONLY.
at this stage head unit volume makes no difference, since there is no audio signal gooing into amp.



if you hear hiss with the gains on all 6 channels set to the minimum, i'd guess your amp is faulty, only way to test it is to set it up on test bench away from the car, so you can tell if the noise is being picked up inside the car, or if its being generated inside the amp itself.

just out of curiosity, try setting all channels to low pass, and tell me if you still hear the hiss.
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      06-03-2011, 12:10 AM   #34
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OK kmarei I will give that a try...
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      06-03-2011, 11:26 PM   #35
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OK I did the rca shorted plugs and the noise is gone!
So that tells me twisted signal wires from head unit are picking up noise or more likely the headunit sucks..

Is there anything else that can be done besides replacing headunit?
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      06-03-2011, 11:38 PM   #36
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Dude, the HiFi head unit sounds great. Perhaps something is wrong with yours, but as a rule, they sound great and we install amps on them all the time.

Just to be clear - you unplugged a HiFi amp to put this in, right? You didn't use a Stereo harness from the head unit?
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      06-04-2011, 01:15 AM   #37
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You could try using noise filters:

http://www.davidnavone.com/cart.asp?24&cat=2

http://www.crutchfield.com/S-wVUGR9G..._diagnose.html
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      06-04-2011, 01:32 AM   #38
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None of which are for hiss...
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      06-04-2011, 08:07 AM   #39
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Quote:
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OK I did the rca shorted plugs and the noise is gone!
So that tells me twisted signal wires from head unit are picking up noise or more likely the headunit sucks..

Is there anything else that can be done besides replacing headunit?
I have been closely following this thread because I plan on installing the same amp to my hifi head unit, and am concerned about getting noise too since there have been several threads about it. So thanks to everyone for all the sharing.

TO Digitaldav, I don't now understand the issue, if the shorted RCA's ( I assume you put these in the unused RCA inputs to the xd600) solved the issue, WHY are you still hinting at a problem with the head unit?
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      06-06-2011, 06:40 AM   #40
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Quote:
Originally Posted by VP Electricity View Post
Dude, the HiFi head unit sounds great. Perhaps something is wrong with yours, but as a rule, they sound great and we install amps on them all the time.

Just to be clear - you unplugged a HiFi amp to put this in, right? You didn't use a Stereo harness from the head unit?
Yes Hi Fi amp is gone. Replaced it with xd600/6. I believe I stated this in opening thread!

I have seen several threads about this same issue, so its not just my unit. I just want to make sure there is nothing I missed when installing amp with harness, and if there is anything that can be done to get rid of the noise.
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      06-06-2011, 06:44 AM   #41
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I have been closely following this thread because I plan on installing the same amp to my hifi head unit, and am concerned about getting noise too since there have been several threads about it. So thanks to everyone for all the sharing.

TO Digitaldav, I don't now understand the issue, if the shorted RCA's ( I assume you put these in the unused RCA inputs to the xd600) solved the issue, WHY are you still hinting at a problem with the head unit?
Because I didnt solve the problem I simply ruled out any problem with the amp. Re-read back a few post on troubleshooting amp.
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      06-06-2011, 07:01 AM   #42
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Because I didnt solve the problem I simply ruled out any problem with the amp. Re-read back a few post on troubleshooting amp.
I missed something here.

If the noise/hiss is gone by shorting the amp unused RCA inputs then it must be the amp picking up noise, correct? You cannot short the OEM HU outputs as they are differential.
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      06-06-2011, 08:13 AM   #43
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Yes Hi Fi amp is gone. Replaced it with xd600/6. I believe I stated this in opening thread!

I have seen several threads about this same issue, so its not just my unit. I just want to make sure there is nothing I missed when installing amp with harness, and if there is anything that can be done to get rid of the noise.
he was talking about the HIFI headunit, not the amp
is your setup HIFI headunit->technic harness-> XD600/6?
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      06-06-2011, 08:59 AM   #44
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I wasn't clear if the unused inputs were shorted or the used inputs were disconnected and shorted.
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