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Where to get Twisted and Foil Shielded with drain wire cabling like GM?

CoveredAV

Full Member
Joined
Sep 2, 2006
Messages
251
I want to add an amp, and I want to extend the factory Low Level Audio Signal wires to this amp.  I noticed that GM encases their Low Level Audio Signal wires inside an aluminum foil shielding with a drain wire.  The GM wiring diagrams also indicate that the signal wires are twisted.  I want to replicate these factory precautions against noise in the signal wires I add to the second amp.  Where can I get this GM cabling?

I've thought about using shielded CAT 6 cable, that has four twisted pairs.  My concern though is that the individual wires in network cable like that are too small in gauge.  And there is no drain wire, for whatever that is worth.

Since GM has strung their audio cable into MILLIONS upon MILLIONS of vehicles, the cable has got to be available somewhere.  Has anyone else tried to find something similar?
 
Not sure where you might find the GM cable, but I've had success with DBLink double shielded twisted RCAs. I use their CL series, they have each wire shielded and have an internal wire and twist, and are then wrapped in a second shield before an outer casing
 
Simple twisted wire will do.. The extra stuff is not necessary..

A pro installer back in the mid 90's showed me a trick he was doing that made better sound than any of the RCA stuff available back then...

Took 2 18 gauge wires, tied one end to a post and stuck the other ends into his cordless drill and twisted them until they were tight... Best sounding low levels available at the time.

Because they are twisted they cancel out any RF picked up by the wire since both pick it up.

Only low level stuff is twisted in the OEM wiring and it is like 24 gauge...

Network cable IS available multi strand and I use it in my truck for low power stuff in my truck because it is cheap...

Rodney
 
I twisted my pairs tight because otherwise they fall apart... I was MECP certified back in the 90's but pretty sure not much changes. Was at the "pro" level certification. If you do twist in this manner you will find you can only go so tight. Do not force it and let the twists untwist a little... It will prevent issues later. If you don't twist hard enough they won't hold together.

In an installation you SHOULD try to run your power and especially low level signals ATLEAST 6" apart so any noise in the power doesn't get picked up in the audio. Any time they have to cross they should do so at a 90 angle so as to expose the audio to as little of potential RF noise as possible. The shielding really has little benefit for most installations. In the case of the OEM console cable notice that ALL of the audio cables are twisted.

I recently tied into my low level and high level audio cables in the portion of the cable that stays mounted to the truck when the console is removed. I have a small slice cut into the carpet and was able to feed all 8 pairs of twisted wires to the rear of my truck where they all come out near the seat belt mount. I used a coat hanger to setup a pull string that allowed me to pull all of my wiring. You will want to wrap in a protective plastic wire loom. 

I currently have all 8 pairs behind my seats even though I am only actually using two pairs to power my subs. I did this to allow me much flexibility.

As to the power from the deck.. What I am finding with my '03 is that the low levels are too high for RCA inputs. On either of the amplifiers I used the amplifier kicks out at less than 1/3rd volume on the radio so I had to use line level convertors. I used a PAC line level convertor and it worked great. I turned the sensitivity of the amplifiers all the way down to pick up less noise and adjusted the PAC line levels to match full volume on the deck to a good level on the amplifier. The amplifier I was using however was not powerful enough to power the OEM speakers so it is shelved for now.

My Sub amp has a high level input on it however... When I tried the powered outputs from the amplifier to the subs it was too powerful for my amplifier. I was trying to use the crossover built into my BOSE amplifier... Which was unnecessary since this amplifier has its own built in cross over.  At about 80% radio volume the sub amp kicks out while running off the sub amplifier channels. It is currently set to pull the low level audio from the rear channels on my radio but this is too low for the high level inputs on my sub amp. Since I have tapped into the powered wires for front and rear I can use either the front or rear amplified pair to power the high level input into my sub amplifier but have not done it yet. As is I am running 1 10" sub off my 2x250 amplifier and the output is near what the factory BOSE is... I REALLY need to change the input I am using because it is too low..

You can start to see why I pulled wires for both low powered and high powered side of the factory amplifier. Plus I can disable the factory amplifier and use an aftermarket amplifier relatively easily without pulling my console all out.

One other "gotcha" I am running into... I used the AMP ON line from the radio and it seems to turn the factory amp on and off consonantly. I am getting turn off thumps on my sub amp that I wasn't getting before about every minute or so. I BELIEVE this is due to the system chime setup so I will be setting up a small relay to only turn on with the RAP input I have available so it won't turn the amplifier on without the radio being on.
 
If you are referring to me...

I am getting the turn off thumps only when the truck and radio is off... Thus assuming it is tied into the chimes of the radio. I will be isolating with a relay.. I will end up having to run an RAP wire to the amp but I don't fancy pulling the console again right now so we will see what happens if I have the amp turn on turn on a relay instead.

From what I have read the head unit outputs high level audio and you really need a line level convertor if you are trying to use it as a feed to an amplifier. and I demonstrated that with my amplifier. My Sub amp seems to like the powered outputs better than the "low level" outputs from the radio.

This system has issues right now and I may not get any deeper into them simply because I tried to get something up and running for nationals and will be going a little more in depth as I can. I am likely going to build an Amp box that will be in the bed and has more than enough power to power whatever speakers I end up with.  I am currently staying with the head unit because I am looking to capture the databus traffic so I can use them with the CARPC that will be replacing the head unit.

The rest is irrelevant to my issues. 

 
First of all, the community at CAFCNA rocks!  Plain and simple.

I've searched all over the net for answers on wiring up a GM factory Bose stereo, and no where else does a a discussion this lively, and this informative show up.  Only here.

And what is interesting is that this observation has held true for more over a decade, dating back to the late (and really great) Sperry's time here.  It was Sperry who first came up with the wiring method of upgrading the Bose Audio to the Luxury Bose Audio.  And then there was the Nav in the Av thread from years ago.  All of the activity here ended up spreading to other GM truck  forums, but it is interesting that it seems to have started here.

Something about the DNA in AV owners?  Half of them are MCEP?  Or just crackerjack electronics wizards?  I don't know, but I'm just happy to be allowed in your company, even though my AV is permanently covered.

So, to answer some of the questions on the table here (speaking as the OP)... what I've decided to try and find is CAT 7 cable, 22 or 23 AWG, either 7c or 19c stranded, S/STP or S/FTP, where each pair is individually foil shielded, then the ensemble of four pairs is foil or braid shielded, and there is a drain wire included in the bunch.  I think I've found what I'm looking for from a vendor who advertises a so called CAT 8 cable, even though CAT 8 hasn't been officially formalized into a standard yet, but apparently soon will be, as the proposed specs are available.

To avoid the solid core versions of network cable, I intended to buy patch cables, which are usually stranded, where bulk cable is not, and just cut the RJ45 ends off.  I believe this will be far less expensive, and perhaps far more effective at noise shielding, then all the marked up marketed monster cable at the car stereo stores.

Another reason for avoiding the stereo store is that I'm not using aftermarket amps.  Both my main amp and my add on amp are GM Bose, with no RCAs.  So if I go from bare wire to RCA coupling to RCA Coupling to Bare wire again, that introduces 6 connections x 8 signal wires = 48 unnecessary splices or connections that invite signal degradation.

The challenge I've run into with CAT 6 shielded patch cables is that I haven't found any larger than 26 AWG.  I think that's a bit thin.  Wouldn't 22 or 23 AWG would be enough though?  Especially for a run not more than 14 feet total, including all bends and strain relief loops.  Low Level Audio Signals by definition are very low power, arent they?

I think it is impractical for me to run power and signal to the amp separately.  GM didn't do it in the factory harness.  I'm more or less trying to replicate the factory harness.  GM used shielding, twisting, and a drain wire on the low level audio signal source cables.  I'm trying to go one better than that, by going with a double shielded (SSTP) signal cable (ie, the CAT 7/8 patch cable). 

I arrived at this idea because I've always bought CAT 6 STP shielded patch cables, and when I left one of them outside for 8 years, the PVC jacketing cracked open and I saw how they were shielded.  When I cut upon a GM shielded audio cable, I noticed the same type of shielding, only the GM conductors were heavier gauge (if that is even possible... GM does like to skimp on copper!).

I just want to run from the center console down behind the driver's seat, into the bottom of the B pillar, then along the driver side rear passenger door trough under the threshold plate, then up the C Pillar to an area behind the back seat.  I don't want to run power all the way around the other side of the vehicle.  My additional amp is only 175 watts total, of which only 100 watts is allocated to the sub I'm adding, and the rest of the channels are not going to be used.

I appreciate your spirited discussion, and all of the tangents too.  Please keep posting your thoughts and experiences!

Redheadedrod, I especially appreciated you sharing what you found with your project, which has made me aware of other concerns, like the Radio On signal cycling when the Radio is OFF.  I had not anticipated that.


 
For audio use twisted pair should be enough. Shielding and such is not necessary for normal usage. If you look at the GM harness in the console you will notice that the low level wires have the foil and drain wire on them. They also seem to be about 20-22 gauge wiring. In the console I have they paired the front and rear channels in their own foiled groups of pairs. The high power leads were just twisted and looked to be 16-18 gauge wiring. I would NOT go smaller... Bigger is better.

I would NOT use the LAN cable at all for audio. The ONLY place I would even consider using it is for the add on AUX port. You can buy reasonably priced speaker cable that comes twisted with a foil cover on it if you REALLY want but it is not necessary. Especially if you can keep your audio cables totally separate from power. In the console harness they are all wrapped together.

As to adding the LUX audio if I had a cheap one to play with I might try to add it. My suspicion without looking is that it just requires the harness that runs from the radio to the console and within the console and the LUX amplifier. Everything else appears to be the same including the RSA and the radio. The rear channel on my BOSE amp seems to be dead. Even though I get audio from the low side and can hear it in the RSA the amplifier doesn't output anything. I even jumpered the RSA unit.

I have played with COAX style RCA cables and compared to very cheap hand made twisted wire and the cheap hand made twisted wire beat it every time without comparison. Even very expensive Monster brand wire. This was back in the 1990's however but based on that I would only use twisted wire pair when doing audio.  I am using 18 gauge hand twisted wires for both my low and high level wires...

Rodney

 
fishntools said:
The LNA I was referring to is a Low Noise Amplifier used to amplify RF signals in the micro scale (.000001) at 0.01-100 GHz DC/AC; not the Local Area Network.

What do you mean in regards to "amplify RF signals in the micro scale (.000001)" ?  ???
 
All I am saying is that I was shown by a pro sound guy that not only competed in car audio and won the 1991 internationals but he also had been setting up recording studios for many years before that.

He demonstrated how the simple twisted wire carries audio in a lower level situation much better than any coax available at the time. And most of the high quality Audio RCA's you see today use twisted cables. He had access to some pretty amazing equipment and it convinced me.

Video, RF and other signals are completely different animals and COAX may work much better for them. There is a reason why GM uses simply twisted wires instead of coax for their cables...

Rodney
 
fishntools said:
My bad, uV as opposed to mV; millionths as opposed to thousands of a volt. Yee Haaa, now that's some high resolution precision I tell ya, and a quick little bugger too!

My point was, if it could reliably shield and transmit such small fast signals in a automotive environment a fat, slow ars audio signal shouldn't present any problems. If i'm not mistake, although I might be, 75 ohm coax is also used for video applications.

Gotcha.  The RF engineer in me is used to seeing that sort of thing represented as something like -30 dBm (which equals a microwatt).  (y)
 
Ok, this thread that I started mushroomed quite quickly into a nuclear explosion of related issues, much of which, like a nuclear mushroom, went way over my head.

But as the dust settles, can we talk about all the different issues that were brought up, because they all seem relevant to what I'm trying to do.  A couple of topics that are dusting my brain at the moment are:

1.  High level vs low level.  Whose level are we really talking about anyways, where Bose's low is too high for an amplifier's low?  This is where I really need more understanding...  

On the one hand, I read that the head unit "low level out" in a (non lux) Bose amplified system is +5 to +6 volts on the positive wire and - 5 to - 6 volts on the negative wire, and the reason for both the higher voltage and the balanced, "differentiated" output is to reduce noise on the signal wires as they snake their way down through the vehicle harness to the amp.

On the other hand, the less far credible hand by the way, the hand that was attached to the mouth of a "professional car stereo" installer when I called their shop... the reason for the 5+ volt "low level" outputs on the factory head unit was so that "GM could reduce parts inventory, to use the same head units with or without external Bose amplification."   I call BS on that.  Just one look at the number of GM part numbers for a TNR alone is enough to assure me that GM wasn't trying a one size fits all approach.  At least 8 different verified part numbers for NON Y91 TNR head units alone, never mind the INRs or the Y91 versions of both TNR and INR.  

Still, 5 to 6 volts is way higher than 2 volts.  Might be enough to drive factory speakers.  Yet, I've read from more scholarly sources than an installer that a 2 volt signal sent across a wire is far more susceptible to induced noise than a higher voltage signal.  Yet on the third hand, I read from an installer who takes apart various brands of amplifiers... that the negatives are common inside the box, meaning the signals are unbalanced.  (He did NOT say he took apart an 03-06 Bose non lux amp, so that is still an up in the air question for me.)


2.  Remote turn on woes.  I don't think it is a wiring resistance issue or a cut in and out issue.  I think it is a "whenever the door opens, a chime needs to be ready to ding, so it's time to turn on the amp so it can be ready to ding" issue.  It seems likely to me that the Bose factory amp is turning on too, only we can't hear it, because the factory wired it in such a way that we wouldn't complain about it, costing GM a dealership warranty visit when the vehicle is new.

And this is why, getting back to the title of this thread, I am endeavoring to copy GM's efforts to shield agains noise in every reasonable way possible.  Rather than dismiss GM's techniques as overkill and unnecessary, it seems to me that GM wouldn't bother to spend the money if they could increase profits by reducing even 10 cents per vehicle, which when multiplied by millions of vehicles over several model years per design cycle, adds up to quite a bit of money.  GM wouldn't leave that money on the table.  Yet they spent the coin to shield their audio signal wires with higher voltage, differentiated balance (I think), twisted pairs, foil wrap shielding, and a drain wire.  

That's a lot of effort and cost.  If something less costly and troublesome would do just as well, doesn't it seem like GM would have done that instead?
 
1 Think of it this way, a non lux bose headunit sends a not so low signal to a amplifier which in turn amplifies it along with all the distortion. If you use the hi output it's going to do the same over with more distortion and sound like crap..

So if you decide to use the PAC unit it has gold plated terminals so use a gold plated rca patch cable since I think your new amp will have also.

2. You have to find a IGN/ACC power source to switch on the AMP because the headunit and AMP has constant power, that is why the chimes work without the AV being on.

You are waaay over thinking this, but I'm no rocket scientist. LOL
 
Just what does volts have to do with sound quality. ???
 
Did you mean ohms. ???

Yeah I still like ya, but you are not making sense.
 
MS03 2500 said:
You are waaay over thinking this, but I'm no rocket scientist. LOL

I think that says it all...

The same head unit is used in trucks without the BOSE system and no amplifier at all.. So yes the low level output IS high enough to power speakers... There are some threads on the forums on how to bypass the BOSE amplifier. The sound is better but the volume is significantly lower that way.

Every time you amplify the sound you are amplifying any noise in it and inducing additional noise so the closer to the source the better off you are.

This same head unit will power the non-lux and the luxury versions of the BOSE system.

Having said all that... Don't worry about the foil shielding. Just use the twisted wires and not worry about it. Remember, the wire harness has all sorts of other signal wires next to it... If you splice into it you won't be running next to all of that wiring anymore and will just have audio cables...  In the factory installations that don't have an amplifier with the same head unit they just use simple twisted wires without any shielding so it should be fine...  

As to the amp turn on It seems to click on and off every minute or so when the truck is off.

I made use of the BCM output to the sunroof power relay which is the ONLY RAP output in the vehicle. It normally powers a relay that powers the sunroof. My truck doesn't have a sunroof and doesn't have the sunroof relay so I put a .25 amp fast blow fuse on the output and run it to a standard relay to power my RAP outputs. If you have a sunroof you can power a separate relay from the output of the relay. While the BCM can probably handle more than one relay on the same line I wouldn't push it.

Anyhow I plan to use a relay that will be energized off the RAP signal to allow the amplifier to come on with the radio. When energized it will connect the amp on line. Thus the RAP signal has to be engaged AND the amp turn on for it to light up the amp. The other option I have is to use this PAC unit I have that has an amp turn on designed into it so when it sees audio it will trigger the amplifier to come on too.

 
When you look at the output voltages of a head unit higher is better to a point.. Go too high and your no longer "low level"

The lower the voltage level the bigger ratio any RF noise will be in that signal.

So imagine you have a .25 volt injection of RF noise into the audio lines... 

At 1 volt output you are at a level equal to 1/4th the output of the head unit. Very noticeable.

At 4 volts now your noise is 1/16th the output of the head unit. Much less noticeable but same noise.

The amplifier will amplify everything it gets, Music, noise etc..  And with higher voltage you are able to lower the input sensitivity which can also help to keep noise out.

So yes, higher output from a head unit can make a drastic difference in the level of noise the amplifier picks up.

Make sense?

But the issue is the voltage level needs to be something the amplifier can pick up. I believe my sub amp can only accept 4volts in and the 6 channel amp I have will accept 5 volts..  But if the head unit will put out 6 volts it is still too much for either. Thus needing to treat it as a high level output...

ROdney
 
I don't think so but I'm no rocket scientist. Voltage has noting to do with sound quality.

A multimeter is useless when dealing with sound quality.
 
redheadedrod said:
The same head unit is used in trucks without the BOSE system and no amplifier at all..

This same head unit will power the non-lux and the luxury versions of the BOSE system.


This has not been the case for dozens of people who tried to upgrade to the luxury version of the Bose system with their existing UM8 TNR Nav head units.   They destroyed their new luxury amps.  Instantly.  As soon as they hooked up their signal wires and turned it on.  Gone.  Game over.  Start over.  Learned the hard way.

What was discovered is that there is indeed a difference in TNR head units that look and function and appear the same on the outside.  What was also discovered is that one type of head unit could be altered to the other type, but the alteration was a special procedure that very few people knew how to do.  

So few, that I only heard of one person who figured it out.  People would send this guy their $1,000 TNR head units, and he was able to do something that converted them from Non Lux to LUX, so that they wouldn't blow up the next LUX amp.   The procedure may have involved opening up the radio, it may have involved some type of electronic programming tool, it may have involved utiliizing the service menu, it may have involved hard soldering... I don't know.  The secret never got out to my knowledge.  But the point is, there was indeed a difference between identical looking head units, and people paid the price to learn that difference.
 
You getting the idea he does not know what he is talking about.


Rodney Rodney Rodney  :E: :E: :E:


 
I have posted a couple times that my impression was that the LUX and non-lux use same head unit... And I asked if anyone knew differently to correct me... SO it is not my fault if I post my assumption with a request to comment if I am wrong and no one does.

The wiring stuff I look at shows the same unit and it was my impression it was a programming issue if anything.

But I am certainly willing to admit I don't know much about the LUX system. And just learning about my current system more than I thought I knew.

So when I say "Assume" and "Believe" feel free to correct me... It means I don't know for sure...



Rodney
 
Stand corrected no they are not, but I'm not going on and on about this and do posting battle with you. Never assume.
 
MS03 2500 said:
Stand corrected no they are not, but I'm not going on and on about this and do posting battle with you. Never assume.

MSO3, I know you said "never assume", but I'm going to assume that your quote above is not directed at me, I hope, because I have no answers to battle with!  Only questions.

And I also hope that you do not withdraw from my threads due to battles with anyone else.

Put it this way:  You have 33,600 MORE posts than I have.  If you only posted in say, 1 out of every 5 threads you read, and say the average thread has 7 posts, that means you very likely have read over ONE MILLION posts, literally, of user experiences with this vehicle.  That's a lot of experience you've processed. Never mind your own personal experience, in which you have dotted every i and crossed every t as far as upgrades, tweaking it to your needs.

For example, I entered your last bit of advice (AOEM-GM24) in the advanced search page of CAFCNA.  I'm reading and marking posts from you made over a decade ago that have more information than what you post today.  You've been there, done that.  It must get boring for you to answer the same questions over and over!   That's why I'm trying my best to do a search, but it's hard to catch up on a million posts in a fortnight!

So, if I ask a question, and you give me advice, and I still persist in asking more questions, and don't seem to follow the advice right away, the gap to be bridged isn't my confidence in your information.  On the contrary, the gap to be bridged is my personal understanding.  I kind of like to understand and know what I am doing and why, rather than just go head long and do it.  So I hope you don't get frustrated with my struggle to understand.  Have patience with me.

Everyone, have patience with me.  I'm not the brightest bulb in the tree, but with enough juice (information), my filament will light.   Eventually.
 
No it was not directed at you but the post before it, it's just frustrating.

I do not read every post usually I wait until the original poster ask another question then I read them.

But a stock Bose system is not that sensitive enough to need a high end wire, they are for the masses.
 
We or I still like you. I can tell you have a electrical background of some sort. But sometimes it bugs me when members( not you) post something that is totally wrong.

My apologies if you thought it was you.

BTW This type of cable is not needed the non LUX bose system not high tech and really silly to be considered tech anything. It's the worst design I ever saw which is why I went with the LUX system in my 03.

I always say I can lead to water but I can't make you drink.
 
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