Hey guys,

I've been reading and searching through these forums for days with EXCELLENT results. What a resource!

I just have a question out there for any audio experts. Or basically, some advice:

I want to add an aftermarket amp to my 2002 A4 NON-Bose, and I have determined the EASIEST way to get line-level RCA's is to tap into the line-level inputs of the stock amp located in the trunk. For the remote turn on lead, it appears the easiest thing to do would be to tap into the same lead at the stock amp too. The aftermarket amps I will be adding is a one-channel for a sub in the trunk and a two-channel to power new fronts.

The above setup is the easiest, but it means I will be running my entire stereo system off of two-channels, the Rear Left and the Rear Right. The Front channels of the Symphony II will be inactive in the above setup, which means I won't be able to fade through the H/U, but that's OK because I can just tweak the amps as needed. Also, the rear speakers will all still run through the stock amp, so no problems there.

Now my question for advice is this: Is this going to be a problem? I've done a lot of thinking and this seems to be the most logical setup with the least amount of wire-tapping or mod work. I won't lose my stock amp and I won't have to rewire anything in the back of the H/U. My only worry is if it is OK to run the entire system, including the FRONTS, off of the rear channels.

I wouldn't think this would be a problem since the rear channels are in stereo and 99% of all recordings are simply two-channel anyway (left and right channel). But is there anything I'm missing from the above setup that might cause some issues? Is it logical that I can tap into the rear line-levels to run my whole system, without losing signal to the stock amp?

Since the B5 and B6 Audi NON-Bose systems are very similar, I'm sure someone in here has either done the above with good results, or tried the above and failed.

Best wishes and I *really* appreciate any advice from you pros out there...

Chris

I'm not looking to upgrade the front speakers right now, but I have a question for you: why don't you just tap into the front line level HU output in addition to the rear? Instead of 'daisy chaining' off the sub amp you could use two separate sets of lines. That will give you fade control. Are you concerned about the phasing issues that DonP talks about in his tech writeup? I have been contemplating upgrading the fronts to a set of Adire Kodas in kickpanels and an amp, but I want to keep the stock HU look, and I'm leery of using it's signal to power them. Just like yourself, I've done TONS of searching about adding stereo equipment, and it seems to be the general concensus that adding aftermarket amps and component speakers to the factory HU would be "polishing a turd" (pardon my colloquialism). Let me know what your thoughts are.

What also concerns me is that a number of people have said the stock HU sort of cuts the sub output when turned past a certain volume, in effect "plateauing" it. I don't want that monkeying with my signal. Damn, why can't there be a aftermarket HU spot on match for the sweet looking stock. You just don't get the same level of class with an aftermarket unit...

The reason I want to daisy-chain off the rear amp is because it is EASIEST, pure and simple. I won't even have to rip apart the H/U or the dash, just the right rear trunk cap. I can just tap right in, and put the amps back there. But you are right, it won't give me fading control, but I figure I can tweak it enough with the amps.

Also, what are these phasing issues that DonP talks about? I'll have to look that up.

I don't know about the rear sub being cut off at high volume levels, but could this be done by the rear amp, which powers the sub, and not the line-level signals coming from the H/U? That's what I assume--I would doubt the H/U would limit the signals into the amp, but I could see the rear amp doing that out to the sub...

BTW I think you should be quite pleased with keeping the stock H/U. Not only does it look perfect already, IT WORKS! In that: it has LINE LEVEL OUTPUTS.

That's all you need. I'm probably going to go in to have everything installed in a few weeks and I'll post how everything went.

I'm basically at the point where I'm going to tell the installer to just tap into the rear line-levels and run the system from there. I'm going to replace the fronts, and have the installer probably keep the stock wiring and just splice that to tie into the fronts.

I'm also adding a 10" sub to add a little base and another amp. It's all going to be daisy chained. I did this with home stereos and five amplifiers at one time using the same method with perfect results. The line-level outputs are very low on the signal so daisy chaining them shouldn't be a problem as far as I know... I have also heard from others in the B6 forum that they went with the exact same install and had good results...

built in high-pass crossover if you want to filter the lows from the front speaker amp. I was only saying that if you wanted to retain the fade control, you could also tap into the line level signal at the Bose amp as well, just tap more wires (the front two and the rear two).

About the phasing issues, DonP wrote that he believed the front and rear door speakers were out of phase with one another to cover potential gaps in frequency response. There have been a few others that wrote on this elsewhere on the forum too, try a search to find out more.

Regarding the "plateauing" effect of the sub output, I tend to agree with you. Here's my reasoning: if the line level signal from the HU to the Bose amp is only 4 channel (as in 2 front and 2 rear), and the Bose amp splits the rear signal to output to 4 speakers, with different freq response to each (meaning the 2 rear door speakers and the 2 rear deck subs), and only the subs ouput is plateaued, then the processing must be going on in the Bose amp... Other members of the board said they've tested the line level outputs between the HU and Bose amp and found the voltage to cut when the volume is turned up (plateauing) though, so I guess I'll find out soon enough. Regardless, I'm putting my sub and amp in this weekend (see my post above about my sub :)

Good luck with your install.

That's interesting regarding the voltage plateauing. If that's the case I think that might just be something we all have to deal with no matter where we tap in to get line level. Maybe it's just a property of the H/U.

Oh I forgot to mention I have NON-Bose so my situation may be a little different than you. With the non-Bose the front speakers are powered by the H/U while the rears and a small pathetic sub are powered by the stock amp located in the trunk. With a non-Bose, there are only two line-levels going into that amp, the two rears.

So basically what I will be doing is running my entire system off of 2-channels (the rear channels). I think this will eliminate any phasing issues, but you are right, I'm starting to second guess if I should just hook up some line levels coming from the H/U for the front channels two, so I'll have 4-channels. This way I can control fading right through the H/U, but I guess I can just tweak the aftermarket amp's gain too...

Sounds good. Also, I didn't use the current sensing feature of my amp because I didn't like the results. There should be a remote turn on lead in the wire bundle as well! Use that.

HI EVERYBODY, I just read 13 pages on the audio forum, and after reading this one, I couldn't resist but become a member and help a stranger out with the SAME PROBLEM THAT I HAD.

OK, my brother has a 2001 1.8t with non-bose symphony I system, I'm kind of an electronic freak, so I took apart the rear deck and traced the line input wires to the rear amp with a multi-meter. There are a pair of (if I remember right) blue/x-striped and Brown/x-striped wires that are twisted together. The blue wires are the left and right signals and the Brown wires are the common (or ground) wires, which join into a single pin on the amplifier connector. the remote wire is white. First I tapped into those wires and wired a pair of RCAs and hooked it up to a simple amp/sub system, and these are my results.

Even with the engine off, there is a constant boom-boom-boom-boom coming out of the sub, I have checked and rechecked everything, I even ran the amp from a seperate battery at the trunk. I can't go around the EMF or electromagnetic noise that seems to be inside the signal line. this is so because the signal wires are not shielded, well the twisting gives a little shielding but with a constant +12 and remote +12 volts running millimeters away from the signal wires, u r bound to have EMF.

I was wondering why the same noise intereference is not fed out of the rear amplified speakers and came to the conclusion that the signals toe the amp are balanced line inputs, in which case any EMF or any noise for that matter would be compensated for by it. I do not have any amplifier that has balanced inputs to test with the tapped RCAs, and my head units clips are messed up, so my bro is stuck with the crappy audi system.