dzionny_dzionassi

hello to everyone,
i have amp on my Audiobahn A6004T on garage shelf, have been there for 3 years, since i pulled from my acura legend.
Question would be:
Can i grab signal before amp? i will be running two front and two rear speakers, center and sub will b left on OEM amp.
Plan is to cut wires before amp solder RCA connectors and run it to my audiobahn amp.

Trunk Monkey

iTrader: (1)

Yes you can, but you'll have nasty noise in the system

I'm not sure if this has ever been covered...so you might try searching...

dzionny_dzionassi

everyone got noise who went this way?

Trunk Monkey

iTrader: (1)

If you go pre-amp, yes unless your amp accepts a balanced signal. I'm not even sure Audiobahn knows what that is.


If you go post amp it's been said that it might be an unbalanced signal and that's why people don't get noise, but you'll be subjected to a set crossovers, a non-flat signal, excessive drop off <40-50hz, etc.

Pick up a processor or if you wanted to go cheaper, an Audiocontrol Matrix

dzionny_dzionassi

had jvc deck before in my legend and didnt get any noise, whine. MY deck was providing unbalanced signal to the amp?

Trunk Monkey

iTrader: (1)

Yup

djtsmith007

iTrader: (1)

Unbalanced lines are more susceptible to noise problems. So if any noise is the be had in a system it would most likely be because of this.

Post amp is unbalanced as balanced lines require 3 wires for each channel: pos, neg and gnd. Any noise picked up along the wire will typically be common to both of the wires. Assuming the destination is balanced the receiving device will invert one signal putting the two signals back into polarity with each other. Which causes the common noise to be out of phase with itself, meaning that the noise is eliminated.

TRS and XLR connections are (if i remember correctly) the only type's that are in fact balanced.

I hate cars

And after reading a good post by Jerry today, ours are not true balanced signal so you can use anything with it. I've been wondering how I got away with running unbalanced amps this way but it makes sense now. Unbalanced is more likely to have noise but it's not guaranteed to have noise.

dzionny_dzionassi

i will try to go before amp. Will do that next weekend. I guess i have 50/50 chance of success. i'll post results

dzionny_dzionassi

does anyone knows what kind manufacturer/model can run on balanced signal?

Trunk Monkey

iTrader: (1)

http://www.diymobileaudio.com/forum/...ed-inputs.html

http://www.diymobileaudio.com/forum/...-my-acura.html

jda123

You misunderstood his post. We have a balanced differential signal (2 wires). No, it is not true balanced (3 wires - pos, neg and ground), but it will make noise if the amp does not accept it. The noise is pretty bad.

Your old JL amp, MS8 and BLD all would have been able to convert it.

I hate cars

How about the McIntosh 430 and the cheap Interfire? I've never looked to see if they accept balanced but never had a problem with noise with them. Right now, noise is at an all time low with the BLD, MS8 and the HDs that accept a balanced signal. I can switch the BLD to non balanced, maybe I'll try that and see what happens. I seem to remember a little more noise with the other amps and the other setups but it was not terrible and was significantly lower than running from the stock amp to an aftermarket amp.

niebur3

Noise would only occur if the balanced signal was also a very strong signal. Our is a very weak signal, so it shouldn't be a problem. Balanced signals usually have MUCH higher voltage and some amps can't handle the huge amount of voltage and that causes all sorts of problems, one of which is noise. Our signal is weak, so weak I would advise anyone to run a line driver back to the amp IF they what to get the full wattage they have paid for. If you are truly worried, kill 2 birds with 1 stone and get an ARC audio line driver that can accept a balanced input. They are very inexpensive considering the alternatives.

Trunk Monkey

iTrader: (1)

Wouldn't running a line-driver just bring that higher voltage, noise possibility into the picture? I always just figured that the signal is inverse of each other and the resultant noise cancels itself, but that amplifying that signal wouldn't do anything but amplify the signal and possibly noise if the amp cannot accept balanced. If low voltage doesn't have noise and increasing and higher voltages have noise, why use a line driver? Serious question

I've always heard the use of balanced audio in cars is Kinda stupid. One thing I heard was that its more for long distance runs. Also looks like it attenuates the high end frequencies, but that's online..so no telling if it's true. I just wish our cars would be easy to put in a double-din or single-din lol. So many options i'd love to run over our outdated factory nav

Trunk Monkey

iTrader: (1)

It's 1:30am & my brain is wrapped around this. I think you might be right Jerry. I still don't understand why some people ran into noise though, while others didn't. It would be really cool if someone could test an amp that does not accept balanced WITH & WITHOUT a line-driver.

It makes sense though when you look at the way it works. Rejected or eliminated is the average between the input voltage and (not sure what voltage goes here). Then the difference between the 2 voltages, very small in our case..gets amplified.


Wait. Ugh..I'm going to bed

jda123

It is a post vs pre amp thing. If you don't ask the question then you don't know.

I could have sworn that Matt rolled to the pre-amp after he had the BLD.

The noise is unbearable. If you don't believe me, then hook it up pre-amp to a amp that cannot handle the signal and find out.

We are mixing situations here.

Trunk Monkey

iTrader: (1)

I know I hooked my PDX up pre-amp and that's when I had noise. Clicking, whining, etc through the tweeters. I'm sure there are people here that have amps that will and won't accept balanced. I'd still really like to determine whether putting a line driver before the aftermarket amp on pre-amp signal will reduce or eliminate noise.

jda123

If the line driver accepts balanced diff, then it will be fine. If not, then you will still get noise. RF BLD and the arc are just 2 mentioned on this thread alone that will do it. If your amp will take the signal, then you don't need the the LD.

The BLD stands for Balanced Line Driver.

Trunk Monkey

iTrader: (1)

Right, I know that. But, Jerry & Matt, I think...were saying that they've used amps that don't accept accept balanced inputs and had no noise on the pre-amp signal.

If you're using a BLD, processor, etc then you're fine. It's the fact that do we in fact need a line driver that can convert the balanced to unbalanced?...or is any line driver fine to just boost the signal? I always thought that the amp had to accept balanced or you had to convert the signal with the products mentioned above, but if people are having no noise with amps that DO NOT accept balanced inputs, then it's something else. That's why I wanted someone to test it and put this damn "balanced/unbalanced" bs to bed

dzionny_dzionassi

Put the wrong amp, actualy i have : Audiobahn-A4601T i know it is OLD amp and i noticed that older amps support balanced signal. I know AUdiobahn is not the best brand, since it is sitting on my shelf i have nothing to lose...
Installation is due tomorrow we will see how its gone go. If i will have noise, i will go to besbuy and grab Alpine MRP-F300, and tab signal after amp.

dzionny_dzionassi

installation complete. Outcome: engine off, sounds ok
engine on, alternator whine. When head unit is off you still can hear alternator whine.

Any ideas how to fix?

Trunk Monkey

iTrader: (1)

If I remember right the head unit is never fully off. Could be wrong there though.

Alt. whine is most likely from a bad ground. Is it a whine that changes with RPM's? Or does it sound like a hissing, clicking, high pitched whine that will change on its own?

dzionny_dzionassi

whine is RPM dependant. on only can hear when engine is running.
Tomorrow i will try to add 2 farad cap. Maybe it will help, but i doubt. Change ground point.

Trunk Monkey

iTrader: (1)

Change ground point. What awg wire are you using and where are you grounding??

You can use a DMM if you have it to see if that's your problem.

jda123

The HU is always on for the HLF and Navi (if you have one). The stock amp is always on too.

See if it goes away with the post-amp signal.

dzionny_dzionassi

Changed ground point, even tryed to run (-) from battery. Changed remote wire on different fuse, same thing. I am using 4 awg wire. Even tried to move positive wire under the hood to go as far as possible from fuse/relay box(thought it was interfering). Added aditional ground to my aftermarket amp.

then the key is on ACC souds perfect.
then the key is on ON, i have buzzing sound.
then i start the car i have, buzzing sound + alternator whine.
Bad amp maybe? Any other thoughts?

dzionny_dzionassi

Problem solved with Ground Loop Isolator. No loss in sound quality.
For some reason bass is deeper right now. Happy with results.
I would highly recommend to install ground loop insulator who have problems with altenator whine or buzzing sound in backround. I thought i will lose sound quality, but really didnt noticed any difference. And the main thing is i got my signal before OEM amp. Now i can crank it up with no bass reduction.

Trunk Monkey

iTrader: (1)

If you need a ground loop isolator, something is not right.


GLIs are transformers, usually with a 1:1 turns ratio. They will pass an AC audio signal, but will break the so called 'ground loop'. Unfortunately the windings also act as a 6db octave high pass filter because of thier inductance, and cheap GLIs will indeed cut out your bass. (found this on another site so not sure of validity, but GLI's aren't common in most setups for a reason)

I hate cars

I would have tried different/better RCAs or a BLD first.

dzionny_dzionassi

not sure what BLD stands for, but tried different rcas with no luck.
I tried every thing, even put ferrites on ground and power cable. Strange thing is that as soon i connect ground to ground loop insulator, i get even stronger buzzing sound in my speakers.
Something is wrong with my cars ground?

Trunk Monkey

iTrader: (1)

I'm assuming you mean an initial buzzing when connected, then it goes away??

BLD = Balanced Line Driver (http://www.sonicelectronix.com/item_...te-RF-BLD.html)

Where are you grounded to? Pics?

dzionny_dzionassi

buzzing and alternator whine is gone when you connect GLI, but GLI have two ground wires too. As soon you connect those two wires to the body of the car you get even worse buzzing sound and alternator whine. And my ground wire is connected to the bolt in the trunk. There is another factory ground cable connected to the same spot. Like i said i tried numerous ground locations, cables and even tried to connect 2 farad cap.

Trunk Monkey

iTrader: (1)

I think I know what you're talking about because I'm grounded to that exact same spot. Near the ski-pass?

At times, I'll get a constant whine that changes pitch by itself. Not RPM dependent or anything, it's just a whine that goes up in pitch and back down, over and over. Loud enough to hear from drivers seat no problem. Only happens sometimes and I have NO CLUE what it is. I'm moving my ground this weekend though. I sanded that spot, etc but I think it's just not good. It's not exactly the "chassis" of the car and it's pretty thin

dzionny_dzionassi

yep it is by the ski-pass. But in my case ground spot is not the problem because i tried few ground spots, sanded to the bare metal.
Like always all buzzing whining sounds coming from the speakers are big mistery.
Happy i solved mine, because i really didnt want to tap after amp and it costed me extra 26$

I hate cars

Fuel pump.

Trunk Monkey

iTrader: (1)

You think it's too close to the fuel pump? Maybe that's what my whining noise is. I'm moving my ground to the location where the spare is bolted in the spare well area. Should keep the ground short