1994 Z Bose system question

[darryls300zx]

hi! I'm helping my friend who owns a 1994 300ZX with the Bose audio system. factory head unit needs to be replaced and he's picked an Alpine head unit.

https://www.crutchfield.com/p_500UTE73B ... -73BT.html

This unit has both speaker level and line level (aka RCA) outputs. If he buys the head unit from Crutchfield he gets a PAC ROEM-NIS1 interface unit. So, my question is: what type of signals go from the factory head unit to the Bose amps? That is, are they one of the two noted above (line level or speaker level) or are they balanced differential like some BMWs have?

Thanks!

[NolimitZ32]

They are direct channel (speaker level). The system is pretty simple in comparison to the amped BMW systems that use i-BUS or fiber. Check the wiring diagrams in the FSM in the link in my signature. From what I remember it actually doesn't require anything special except a stepped down input to the amps.

[darryls300zx]

NoL, thanks for the info. Yeah, I've owned BMWs and they use either fiber or balanced differential.

Thanks!

[NolimitZ32]

I have an e39, e53, and e90. About to pick up an f15 for my wife so I have plenty of experience with the various comm BUS systems and the headaches that come along with them. As for the Z32 BOSE system, I looked it up its on page EL-91 in the 1992 manual and I was wrong, it is a bit more complicated than just the remote but not by much. The remote off the AM head-unit is used to power the switch side of the audio relay. Take a look, it should be pretty easy to decipher.

[darryls300zx]

Nol, got it. Turns out it's page EL-73. The Alpine head unit has a remote turn on signal for the amp, or amps in this case. I'm glad that he turn on signal goes to a relay and not to all 4 amps!!! I've attached "Alpine UTE-73BT Connections.jpg" from the Alpine manual. The model is the UTE-73BT.

So, basically I hookup the speaker level outputs to the car's amps. He'll buy it from Crutchfield so the installation gear shown in the second "Crutchfield extra stuff-free.jpg" is included. But, do I need the PAC-ROEM-NIS1 as the interface between the Alpine head unit and the car's harness? Or, can I just do a straight hook up?

Here's the link to my audio project in my F22: https://www.bimmerforums.com/forum/show ... 968a467448

Thanks,
Mark

[NolimitZ32]

Now that is the question. I never messed with the bose amps that extensively and have never had a chance to get my hands on a BOSE facotry headunit so I don't know what voltage the signal comes out at. I imagine its an unamped (1v) signal to each of the amps. If you still have the factory BOSE headunit hook it up to some power and check the speaker signal output with a voltmeter. That should tell you where you need to be with the new unit, then you install a converter which in essence is a stepdown device inline between the head unit and amp to drop the signal voltage. If you feed 4v signal to the BOSE amps you stand the chance of frying them, they will work at first but for how long I couldn't tell you.

[darryls300zx]

I like your idea of hooking a small speaker or a digital multimeter to the output of the factory head unit. I suspect that the signals are line level as sending speaker level signals to the amps would require each amp to have a step down transformer.

Thanks,
Mark