Hello all,

I have been reading up on here about possible methods of tapping into the stock Bose system. I orginally had a PAC OEM-2 module tapped into the inputs to the Bose amp. I was unhappy with this as I did not have much gain control (had to crank the gains on the module to get sound). I decided to tap the inputs to the amp directly and feed them into the Sub amp. All was well and I had much more signal to work with but then I started the car...and the rear speakers had a high pitch whine. I decided to try and localize the issue and I found that if I unplug the RCA into the sub amp right channel the whine went away. It seems like my amp is feeding the whine back into the stock system through the right RCA input. Is this possible?

I have read that I would need an amp with balanced-differential inputs in order to avoid noise but I figured that since I was only using the amp to drive a sub it wouldn't matter if there was a whine in the system.

The amp I am using is a Kenwood KAC-728S that I go used fo $20. Do you think a different amp would help?

Thanks for the input.
Jason

 

Can you clarify for me the diff between these two?

I *think* you mean the first time, the signal from the HU to the 4-channel Bose amp, and the second time, the preout from the 4-channel amp to the sub amp strapped to the sub.

But can you verify that for me?

I don't believe the Kenwood amp has "balanced-compatible" inputs. You could use another amp, or a balanced adapter on this signal to isolate the two. I think you're essentially shorting the R (-) balanced wires to chassis ground.

 

Okay, further clarification.

I am only adding on a Sub amp to the stock system. My first go around I used a PAC OEM-2 that I tapped into the low level inputs for the front speakers to the stock amp. I was disatisfied with the amount of gain control I had with this setup. I then read a post by you that stated that the low level inputs to the stock amp would work as direct inputs to an aftermarket amp. I decided to tap the rear channels directly and feed them to the sub amp. All was well until I started the car at which point I got a whine from the rear speakers. I noticed that if I did not plug anything into the right channel input of the sub amp I did not have any whine.

Basically, I think that my sub amp is introducing noise into the stock system through the right channel RCA jack. If they sell a module that can isolate the RCA line such that noise cannot travel back through them and into the stock amp that would be the ticket. The other option would be something that can take the stereo input from the stock system and combine it into a moaural signal that I can plug into the left input of the sub amp.

 

OK, I see what you're doing, got it.

The balanced signals are indeed apparently not liked by the Kenwood amp.

If your car is a sedan, I would use the signal wires from the 4-channel Bose amp to the sub (these are probably non-fading, too, and are higher in level).

But I doubt the Kenwood can handle the balanced signal.

If your LOC is designed for speaker level signal you might not be able to get enough gain out of it... but have you tried rotating the adjustment screw on the LOC the other way? A lot of LOCs have pots that rotate left for lower resistance and right for higher resistance.

Your LOC on the sub output of the 4-channel amp might work just fine (especially if the screw is backwards). If it doesn't, you need another LOC (Soundgate LOCB.2) or an amp that will take balanced.

 

I am in a Coupe (hence the need for a sub )

The LOC I have is designed to work with Factory Bose systems (according to manufacturer) so it has low level and high level inputs. I am reluctant to tie into the high level outputs of the bose amp as I want to avoid the equalization that occurs.

Right now I am thinking my best bet here is a new amp (didn't really like the one I have anyways). Any recommendations? I have a single JL 10W1 4 ohm sub that takes 150 watts RMS. I was looking at the JL e1200 or the Rockford Fosgate Punch 201S found here: http://www.crutchfield.com/S-mNJWGOC...=100&I=575201S. It says it has differential inputs (doesn't say balanced though).

What I don't understand is that the sub sounds fine. I am getting the whine from my stock rear speakers (still powered by the bose amp). That means that somehow my sub amp is feeding sound back into the system when the car is running.

Anyways, thanks for the help, you really seem to know you stuff on car stereo.

 

Thanks for the kind words.

Your Kenwood (I think) has grounded RCA shields.

So you're essentially shorting one of the balanced lines to ground.

Never used PAC interfaces. Don't know. But I'd still try the **** the other way.

 

Yeah, that seems to be the case. Like I said, I think I am just going to get a different amp.

What do you think of the RF I linked above? Would the inputs on it work or are they just BSing me? Otherwise my only other choice is the JL e1200 unless you can recommend something else. (would like to keep it under $200).

Thanks,
Jason

 

If you have the $$$, get a JL "slash" series amp, those things rock your face off... I recently purchased and installed one and I couldn't be happier.

 

The JL have balanced inputs. The RF, I don't know, but I've heard they don't.

JL is a healthier company anyway, so I'd go with them.

 

Yeah, they seem like awesome amps but I think it would be overkill for me. Like I said before I only have a JL 10W1 which pulls 150 watts RMS so even a 250/1 would be too much power. Plus a ~$400 price tag is much more than I am willing to spend on this project.

I am only trying to give the stock Bose system a little kick-in-the-pants that it needs, not looking to set off car alarms here.

Thanks for all the input though.

 

Now, that's not cool. Your rationalization about why you want what you want doesn't need to cast aspersions on what others want.

The "slash" series does have other improvements, like the regulated power supply. It would sound better, but probably be no louder. The fact is that twice as big an amp only plays 3dB louder anyway.

 

Hold on a minute, I am not trying to bash or bad mouth anyones setup here. In fact I have a '95 Prelude with over 1000 watts in it. I was merely stating that I am not looking to seriously upgrade the Infiniti, that's all. I want to make the mods I do to this car as inexpensive as possible without sacrificing too much. The main reason I don't think I need a slash series amp is that the sub I have won't handle all the power it will put out. The e1200 seems like the perfect fit for the 10W1 (correct me if I'm wrong here).

Like I said, not trying to step on any toes, just stating what I am shooting for.