Problems getting good signal to aftermarket amp

I have a 2001 LS that I'm trying attach an amp and sub I have to the stock stereo. The stock stereo is the Alpine 6-disc changer. I have an older Profile California series, 400W amp bridged to a 12" Pioneer sub. I got the amp and sub used from a friend, so I don't have a manual or datasheets for either.

I have an audio connector in the trunk with two signal wires, that I believe are preamp level signals (is this correct?). I've tried connecting these to the low-level, preamp inputs on the amp. However, the output is very quiet at the sub - it can hardly be heard. I've also tried coming directly off the speakers to the high-level inputs on the amp, but it has the same result - very quiet play. Now, I have had this amp and sub in a previous car and it worked great. I got the signal off the rear speakers, passed through a line-level converter and input to the preamp inputs on the amp. I have tried this setup, also, on the new LS, and it doesn't work either. In fact, this method was even quieter, I had to put my hand on the speaker to tell if it was even working.

So, (call me crazy) I tried putting the high-level speaker wires to the low-level preamp inputs. This did finally get a good volume level out of the sub, but it sounds terrible. I've heard the signal waveforms for preamp and speaker-level are actually different - that the preamp uses signal and ground and the speaker uses differential voltages (positive signal and inverted signal). I don't know anything about this, but it could account for why it sounds like crap. Also, I currently only have one input connected on the amp (left rear speaker to left input). Does it matter how many inputs are connected? Do I need both left and right inputs to get full power out? I did try splitting the one signal I have to both inputs (easier than tearing everything apart to get signal off both left and right speakers), but it didn't change anything. Maybe I need to come off different speakers?

Anyway, does anyone have any ideas what is going on? Could there be proprietary voltages on the factory stereo that won't work with my amp (I noticed the remote turn-on in that connector was only 7V)? I don't think I'm going to ruin the dash and install a new receiver. If you recommend some special conveter box to get correct signals, please tell how and why this will work over the other methods I have tried. I don't want to buy more things that aren't going to work. I've been fairly frustrated trying to get this thing to work, especially after having it in my old car for years working great. I am an electrical engineer, and while I don't know everything about car audio or electronics, you can feel free to use technical terms. If I don't know what it means, I can find others who will. I would really appreciate any advice or help. Thanks.

the preamp and speaker level signals are the same signal - the only difference is that the speakers levels are more amplified and designed to play into the low 4 ohm speaker load, they also contain any distortion the built-in amp may produce.

I suspect your real problem is that the auto turn on wire is only receiving 7V, this will not be enough to turn on the amp. Also you need to make sure your power and ground wires are big enough to handle the power the amp will draw. As a last check, make sure the little recessed knob(s) on the amp labeled level or sensitivity are turned up enough.

I did get around the 7V remote wire, and found a 12V source to use instead, so the amp is turning on. I have played with the gains, from one end of the knob to the other. Connecting it "correctly" didn't provide enough signal or power or whatever, and it was too quiet even with the gain on the amp turned all the way up. Right now, with it hooked up incorrectly, I have the gain down fairly low because it sounds bad with it turned up any more. It does provide a little bass, but it's just not working like it used to. And some songs with higher-pitched bass just sound terrible because it seems to resonate those tones really bad.

im not 100% sure what your situation is, but i was using my stock head unit also, go find a "line output converter" it attaches to one of your speaker wires, and turns it into a preamp signal, then you can plug it into your amp, if you use the speaker level inputs it will destroy yoursubwoofer at high volumes, i did that, and i cracked my subwoofer, no one told me what to do so i just tried it myself, so get the line output converter, better yet get a cheap head unit it'll just work better that way

EDIT:
here is one http://www.virtualoutlook.net/images/add/SNI-35.jpg
another one http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=50552&item=5701135914&rd=1&ssPageName=WDVW

it just turns your speaker signal to a low frequency signal for your amp, hope this helped

I am using the factory CD player as well in the Accord ... the first component it goes to is the audio control EQL, the has high level inputs - this works great. You may have bad amp.

I have tried a line-out converter, connected off the rear speaker wires. However, this worked even worse than trying to connect it correctly. The sub was inaudible - I had to put my hand on the speaker to even tell if it was playing anything. It just seems that the signals are too low for anything I'm using.

And, I'm sure my amp and sub are not bad, I have had this setup in a previous car for a few years, working very well. I'm just trying to move it to my new car.

without being there, it's VERY hard to diagnose .... but if I thonk of something for you check/ try out, I will post it

without being there, it's VERY hard to diagnose .... but if I thonk of something for you check/ try out, I will post it


Yeah, I don't understand why it won't work right, it shouldn't be that difficult. I've been looking at Line Converters, to see if there's any difference between them. The one I bought was from WalMart, so it probably isn't much for quality, but I can't seem to find much details for specs on these that would separate some from others. I guess I need to check voltages to make sure they are up to a good level for whatever input I'm trying to use. But, it's hard to check voltage on a audio signal. Also, as I mentioned, I don't have any specs for the amp, so I don't even know what voltages it requires at the inputs. I've seen that 0.2 - 8V seems common for preamp inputs on many amps, though. I believe the stereo outputs 80W, and there are 6 speakers (2 small center channel), so the 4 main speakers should get a bit under 20W each. So, 20W on a 4 Ohm speaker should be about 8.9 Volts across the speaker - which is what should be put into the high-level inputs. I don't know what is expected at this input, does this sound about right, or too low?

Thanks for the thoughts, anyway.

line converters are just transformers, just be careful - cheap ones have too much (or too little) inductance ... I forget which. The end result is that it can end being a hipass crossover - which means it will cut you bass levels.