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About the Factory Radio...Balanced Line

16K views 19 replies 11 participants last post by  Bisketz 
#1 ·
I've received several PM's regarding integration of aftermarket equipment with the original equipment. I hope this will help answer some questions.

I would like to start out by saying that I'm not a prefessional installer. I've been a car audio enthusiast since the late 80's, I've put in many systems and I'm fairly well versed on theory. If any pros read my posts and see any errors, please let me know. I don't want to put out any misinformation.

In car audio, radios normally put out 3 types of signal: speaker-level, unbalanced line level, and balanced line level.

Most radios have a small built-in amplifier which you hook up to the speakers via the color-coded speaker wires. This is speaker-level output. If you wanted to hook it up to an external amplifier, and the radio had no RCA outputs, you would need one of two things...an amplifier which takes speaker-level input, or a line level converter to change the signal to line-level.

Unbalanced line level is the RCA-style "preamp" signal which is typically used in car audio. It consists of a center conductor which carries the signal, and an outer shield which is usually a ground. The voltage of the signal is typically around 4 volts.

Balanced line is the type of system used in the Element. It consists of a positive wire, which carries a signal, and a negative, which carries the same signal 180° out of phase. The advantage of this system is that any noise picked up by the lines is cancelled out by the two phases. The two signals are combined and are about 8 volts.

When we try to mix aftermarket equipment with OEM equipment, we are mixing 4-volt signals with 8-volt signals. When we hook up an aftermarket headunit to the factory amp, we are sending a 4-volt signal to an amp that wants an 8-volt signal. Anybody who has replaced the radio like this probably noticed that you have to turn the volume up to be able to hear it, and even then it sounds kinda mushy with no real punch. The only way to remedy this is to install a balanced line driver before the amp, but it would be better to just replace the factory amp, altogether. There is no real problem with doing it this way and it has been done many times...it's just not perfect.

Hooking up an aftermarket amp to the factory radio is where it gets tricky. Since the factory HU puts out 8 volts, some amps can't handle the input. A few amps are designed to take a balanced input, but you will have to do your homework to make sure. One option is to use a signal processor such as JL Audio's CleanSweep to tune the signal. Another option is to use a balun (pronounced 'baloon') to convert the signal. After doing some research, I found the PAC AOEM-HON20 which seems to fit the bill. http://www.pac-audio.com/productDetails.aspx?ProductId=561&CategoryID=28

Another area that people seem to get confused is with the term "power antenna". They think that since the antenna doesn't move up and down, that it's not powered. This is incorrect. The EX, SC (and I believe the LX as well) has an amplified antenna. If you don't hook up the power antenna lead on the wiring harness, you will get poor reception.

Well, sorry for the novel. If anybody wants to add anything or sees any errors, feel free to post them.

Alan
 
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#2 · (Edited)
unbalanced are also called single-ended outputs/inputs. And like alan said since the signal of the factory radio is similar to a speaker output in that the positive an negative signal are 180 degrees out of phase but at a lower threshold, i like to use the adaptor shown below with rcas wired in to the factory harness going to the honda amp. it has a switch that allows it to be used for different types of setups, this being one of them. I generally have less trouble hooking up the factory amp with the speaker level outputs if an adaptor such as this is not available but your will not have as much volume control at the low end due to the higher voltage that the speaker level outputs from the after market radio produce. nice to see another person on here that seems knowledgable in car electronics. can wait to bounce ideas off you. :)


http://www.scosche.com/products/sfID1/151/sfID2/159/productID/999
 
#4 ·
I just got my system wired yesterday and thought something was up. After reading this I can see what's happening.

In my system I have a carpc sending audio to a preamp eq. I send stereo audio to the eq and it splits front/rear/sub for me. It also sends out 7v signal so nice and high.

The issue I'm running into is the whole system sounds out of phase. If I fade front to back it seams better but it sounds like one of the speakers it out of phase. I have checked the wiring and the harness is correct for the f/r/l/r speakers, need to verify sub again so I'm a bit baffled. I hook the factory stereo back up and it sounds good and "thick" when I have my preamp eq hooked up the midrange is too high (with levels flat) and voices are strange.

Has anyone else seen this?
 
#7 ·
I dont know that i would have gone thru all the work you did to put a car pc in and bother running it through the factory amp. The 4 channel section of the amp is just an amp chip and the rest that actually makes it have some size is for the sub. get a good 5 channel amp like the kicker zx700.5 and run everything off that. Then you will have plenty of juice if you get around to replacing that dinky factory sub with something nice too. :)
 
#5 ·
So you hooked the factory radio output to the input of the EQ? The factory radio outs as mentioned above are balanced line. Can your EQ take a balanced line in? If not you wil have to find a device that will.

I used an Audio Control Four.1 which can take a balanced line in to do the conversion from balanced line to non-balanced so I can send them to my amp. Mine sounds great and I have no noise at all, which is tough to do on a Honda.

http://www.audiocontrol.com/t34/5250/14150/In--Dash-Car-Audio-Processors/FOUR1i-In--dash-Car-Audio-Equalizer-with-Auxiliary-Input.html

John
 
#9 ·
So you hooked the factory radio output to the input of the EQ? The factory radio outs as mentioned above are balanced line. Can your EQ take a balanced line in? If not you wil have to find a device that will.
The setup removed the stock radio. Here's how it's setup:

CarPC -> EQ -> Stock Amp

Stage 2 - when all of my other stuff gets in

CarPC -> EQ -> JL A6450
 
#6 ·
Wow, that's awesome! I had no idea. I got lucky because apparently (according to a thread on another forum) the amp I installed (Alpine MRP-F300) accepts balanced inputs. I can report that it works and sounds great.

If you're a cheap bastard/college student like I am you could use some op-amps like a TL072 to convert the differential signal to single-ended.

Here's a link to the thread I mentioned above, they've assembled a list of amplifiers that accept differential signals: http://www.e46fanatics.com/forum/showthread.php?t=528285
 
#12 ·
This build is totally custom. I have a double din screen mounted where the stock radio was and the pc components mounted in an SC console (in my EX).

Here's the breakdown if you are worried about price:

Screen - EBY701 - $250
Motherboard - D201GLY - $40
Ram - 1gb - $15
Power Supply - M2ATX - $50
HDD - 300gb recycled from another machine - $40
HD Radio - Directed HD tuner - $75
PreAmp Xover - some inexpensive one - $25
Steering Wheel interface - CarPC JoyCon - $30
Front End Software - Centrafuse - $125 (there are other options out there which are free but I like CF)

Total is about $650 for this build.

You can get away with one of the free front ends (Road Runner is popular) and you don't really need the steering wheel interface, xover, or hd radio. The screen can also be had for about 180 without the dd mount as well. So, for around $400 or so you can have a similar setup.

The goal for this one was to be as wife friendly as possible and not have "computer" stuff everywhere. I'll get some pictures in the appropriate section when done. I still have a lot of tweaking to do on this install.
 
#11 ·
Ac/dc

Matching head units and amps is about matching the voltage potential of the head unit and sensitivity of the amp. The output impedance of the source and input impedance and sensitivity of the amp all play roles. The output of music is AC not DC so its not like measuring a DC on a volt meter which is constant and supplying the correct voltage or putting 4 four D batteries in a flashlight because it a 6 volt bulb. When no music is playing there is no voltage (to speak of) during a quiet passage or low volume setting there isn't much voltage.

Buying a head unit to use with the factory amp and speakers is a bad choice if good sound is what you want. Most people change their head unit to get features and gadgets not on the factory unit like DVD and a large foldout screen readout etc.


Balanced output and inputs work best in a car for a lower noise floor. A "Balun" is a device that changes a balanced signal to unbalanced or vice versa thus a "bal - un" - pronounced.............bal- un


There are a lot of products to help you. Navone Engineering has some, so does PAC and many other companies.



ET
 
#13 ·
So, the Pacific Audio unit bypasses the factory amp and the Scosche uses the signal coming out of the factory amp, sort of a pre-out. Near as I can tell they both deal with only the L and R channels. In adapting an aftermarket amp like a PDX-5, does the sub output not need a converter? Is it best to run to the sub amp from the head or from the factory amp?

(Sorry to drag up an old thread!)
 
#14 ·
#16 · (Edited)
#17 · (Edited)
Hooking up an aftermarket amp to the factory radio is where it gets tricky. Since the factory HU puts out 8 volts, some amps can't handle the input. A few amps are designed to take a balanced input, but you will have to do your homework to make sure. One option is to use a signal processor such as JL Audio's CleanSweep to tune the signal. Another option is to use a balun (pronounced 'baloon') to convert the signal. After doing some research, I found the PAC AOEM-HON20 which seems to fit the bill. http://www.pac-audio.com/productDetails.aspx?ProductId=561&CategoryID=28

Alan
Does this adapter convert sub outs to (or unbalance them)? Based on the product info it doesn't look like it does, but I figured you'd know from first-hand experience.

I'm an idiot - it's literally two posts up...
 
#19 ·
I just read the reviews for that PAC unit on Amazon. Many of them, even the positive ones, mention feedback or noise. Sounds like the most convenient adapter (plugs right into the factory harness, but maybe not the best?
I currently hear feedback from my speakers when the Audio is off. It is possible that the poster just didn't notice it before. Making a change can make us more observant... dunno. I'll probably still try it. It's nice that it runs dual outputs...
 
#20 ·
"If you don't hook up the power antenna lead on the wiring harness, you will get poor reception."

I'm definitely having this issue. I am lucky to get one or two stations barely. Super annoying. SO cavity E, what's the blue line for E3 (ANT SW+B) get connected two then?
 
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