BukvaMan

the noise is not to bad, is there but as soon as u play music it cant be heard. so my other question is cause now im using the same wire that turns the stock amp on for my aftermarket one is there a way of connecting it so my aftermarket amp turns off as soon as i turn off my head unit

frenchnew

Check Wire at the stock amp with a volmeter to see if it actually is switched off.

The wire is in the 20 pin connector at the amplifier (Connector B, pin 7) the wire is Red/Yellow is the AMP ON wire.

Best regards

frenchnew

CaryTL

since center speaker is used for HFL (and navi if you have it), the amp is on whenever the car is on (even when you take out of the key, it could be on if HFL is in use). the amp_mute signal is high (5V) when you turn off radio.

I am adding a simple relay to switch off my amp with amp_mute signal. center is still from stock amp.

CaryTL

I bought stranded STP at cat5ecableguy.com, 100 ft patch cable $12, plus shipping. but I probably won't replace the cable in my car as my test showed cable was not the problem for the noise. I plan to use the cable for my home theater component video...

luvthisstuff

Sorry in my searching around, I wandered off the 2nd gen forums....I know nothing about the 3rd gens.

Ignore everything I said previously.

I said I was new, just trying to offer some help. No reason to be a D-Bag about it.

ef-tl

Gotta chime in here... and I hope I don't sound too abrasive... but, the idea of using twisted pair wiring for audio applications is, well, wrong.

The reason twisted pairs of wires are used in networking and telephone wiring is to reduce crosstalk, not reject interference from outside sources. Perhaps this can be best illustrated by the fact that there are two types of twisted pair cabling, unshielded (UTP) and shielded (STP) .

In telephone applications you may have 20, 50 or even 200 pairs of wires in one cable, packed *very* close together. with networks you only have 4 pairs (only 2 used (TX, RX)), but once again, they are very close together, and there are usually many cables bundled together in cable runs. To prevent the signal in one pair from bleeding into another, the pairs are twisted, with the twist causing the magnetic field induced in the cable (from the signal it carries) to cancel itself out at every twist. It would look somthing like this:

Example 1 (twisted):
+ - + - + - + - + - +
- + - + - + - + - + -

Example 2 (untwisted):
+ + + + + + + +
- - - - - - - -


Another cable "on top of" example 1 would receive zero net effect, because the field cancels itself out every twist, and therefore would not induce a charge in the cable above. However, a cable "on top of" example 2 would recieve a net positive charge, because the continuous positive magnetic field would induce a charge in that cable.

Notice that this has no affect on rejecting outside interference. The goal of the twist is to cancel out the electromagnetic field that the cable makes, not to shield the cable from an external electromagnetic field. Make sense? Also, remember the cancellation effect is between pairs, not between the two wires that make up a pair!

So, the only thing twisted pair could achieve in a car audio interconnect is to prevent one channel from bleeding into another, however, I don't believe this has ever been mentioned as an issue in a stereo system, nor ever mentioned as the reason for using twisted pair wiring in a car. In addition, with UTP wiring, you actually get no benefit of interference rejection, that you would gain with a good set of standard, shielded RCA interconnects.

CaryTL

I believe twisted pairs do cancel outside noise. but it doesn't matter to me, as my ears don't detect any problem with CAT5 in my car, and my ears are the ultimate judge

ef-tl

Yes, ears are the ultimate judge, and in the absence of interference, CAT5 will work just fine, in fact, I guess it is rather handy to have 4 pairs of conductors in one thin wire... easy to route from the head unit to the amp. However, typical CAT5 cabling is unshielded (UTP), and it is rather fragile for a car audio application, and it usually doesn't come terminated with those handy RCA jacks

That said, I just wanted to point out the fact the the idea of the twist in the wire reducing interference, is, I'm afraid, incorrect. There is simply no factual basis for this.

I beleive the idea must come from the fact that when installed in computer networks, there is virtually no interference, even though the cable is unshielded, hence, people must think it is the twist that does it. However, this has little to do with the cable, and much more to do with the system as a whole, which is "balanced." In fact, in a balanced system (like XLR audio or computer networks) the wire twist ensures that each conductor receives the same amount of interference!

A balanced system is really quite ingenius. On one conductor the signal is sent normally, on the other the inverse of that signal is sent. Any interference received should be equal on each side (remeber the twist to ensure interference is picked up equally), so at the destination, you can subtract one signal from the other, and the difference between the two is interference (they started out equal but inverse), which can be filtered out. Car stereos and amps simply do not have the electronics to do this.

Now, it is true that in a balanced system, you must have a balanced cable, which means pairs of conductors must be electrically "equal", as in UTP CAT5. However, car stereos and amps are not constructed to work as a balanced system, hence using a balanced cable between the two offers no possible benefit.

bluenoise

Another thing I haven't seen mentioned (or I skimmed too quickly) is the idea of gain staging to maximize signal to noise. The idea is to keep the signal as loud as possible through all the stages of its path in order to minimize the amplification of noise. If the source is trimmed down and so is any converters (LOCs, for instance) along the way, the input trim on the amp will need to be cranked up to make up for the losses. By turning up the input gain on the amp, the noise at the input will be amplified, too. With proper gain staging, however, the input trim on the amp shouldn't need to be upped much at all.

When I see systems with excess hiss or noise, I tend to find the gain staging is wrong. Here's an easy example: On many PCs, people have the system volume turned down to some low level, but the volume control on the speakers is cranked up. These speakers often have a little hiss coming out of them along with GSM cell phone chatter. By turning the speakers down and setting the PC's volume to maximum, the hiss is gone and the chatter is greatly reduced. The added benefit is the sound card is (probably) using its full DAC resolution now.

wyzard

Great site that can help everyone!
http://www.termpro.com/articles/articles.html

This one in paticular deals directly with this thread. NOISE!
http://www.termpro.com/articles/noise.html

Live the Ten commandments of noise prevention! I've been doing this for 15 years and there is no substitution for good planning.

Really though, the noise link is fantastic. Keep power away from RCAs, ground properly, and adjust your levels correctly. You will be golden.

CarlyTL is also correct on one point. The KISS (Keep is simple stupid) method is always best in car audio. Adding more components into an already problematic installations usually just compounds the problem. I have no probelms with the navone LOC though. A great solution for the TL.

CaryTL

I've been trying to eliminate the ground loop in the past two weeks... tons of sweat and yet still no luck.. tried grounding amp to different places, and now I also ground HU to same ground point of the amp, this should make the ground level same, but engine noise was still there. I finally grounded negative wires of HU line output to HU ground wire and it helped quite some, but still if I have radio off, I can hear the engine whine. I might put back the ground loop isolators. or just back to stock amp + LOCs... this would be much more work though, as I've spliced dozens of wires

CaryTL

BTW, for the line level signal cables, I've tried shield audio cable, UTP and STP CAT5e, and I couldn't hear any difference among them.