C5 head unit 'mixer' or wire connectors?
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From: Erial NJ
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C5 head unit 'mixer' or wire connectors?
I have a tablet PC which I run an Atlas program on and connect a GPS unit to get directions. The program has the ability to speak directions. However, since the C5 is not a quiet car, once I am driving, even with the PC volume all the way up, I can't hear the directions. I want to use the car's amplifiers and speakers for amplification. Is there a device that would allow me to mix the PC sound with the normal audio program? For example, if I am listening to the radio, I want the PC sound to be heard above the radio program. I have the service manual, so I see how the preamp signal goes to the Bose signal processor and then is returned to the head unit for the twiddlers. I was thinking of building a mixer to go between the head unit pre out and the Bose signal processor input. However, if such a device already exists, I wouldn't have to build one. If no such device exists, then I would need the connectors to connect to the wiring since I don't want to cut any wires.
Thanks for any info.
Thanks for any info.
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: C5 head unit 'mixer' or wire connectors? (NassauBlue)
What you want to do is possible, but not by an amateur. You would need to sum your PC sound cards output with the pre-amp outputs of the HU. It will take 6 1/4 watt resistors, four 10uf electrolytic capacitors and cutting up of the stereo wiring harness to accomplish what you want to do.
The resistors would form a summing network that adds the PC sound to the four pre-amp outputs. The value of the resistors would have to be experimentally figured out. The HU pre-amp outputs are low impedance as is the output impedance of the PC sound card. The four BSP inputs are high impedance. You would need a small resistor, start with 470 ohms, in series with each pre-amp output. This will require cutting the wires in the harness. Next connect the four + leads of the caps to the end of these resistors connected to the BSP. Connect one lead of four, say 2200 ohm, resistors to the - lead of the four caps. Next connect the other lead of these four resistors together. This is the junction to connect the PC sound card to.
The resistors would form a summing network that adds the PC sound to the four pre-amp outputs. The value of the resistors would have to be experimentally figured out. The HU pre-amp outputs are low impedance as is the output impedance of the PC sound card. The four BSP inputs are high impedance. You would need a small resistor, start with 470 ohms, in series with each pre-amp output. This will require cutting the wires in the harness. Next connect the four + leads of the caps to the end of these resistors connected to the BSP. Connect one lead of four, say 2200 ohm, resistors to the - lead of the four caps. Next connect the other lead of these four resistors together. This is the junction to connect the PC sound card to.
Thread Starter
Instructor
Joined: Sep 2000
Posts: 147
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From: Erial NJ
Cruise-In VII Veteran
Re: C5 head unit 'mixer' or wire connectors? (99HT)
99HT,
Thanks for the information. Just so you know, I am an electrical engineer. My original circuit idea involved using op-amps as a buffer, but that was when I didn't know that the head unit output is low impedance and the BSP input is high impedance. I like the idea of using passive components better than active components. I drew the schematic of the circuit you describe. I would want to keep the PC input stereo, so I would have two sets of two 'PC' input resistors together.
Thanks again.
And, if anyone knows where I could get the plug that goes into the radio let me know. I don't want to cut the stock wiring. I want to be able to go back to stock if I choose too. Besides, it would be easier to make the circuit outside the car and then just plug it in.
Thanks for the information. Just so you know, I am an electrical engineer. My original circuit idea involved using op-amps as a buffer, but that was when I didn't know that the head unit output is low impedance and the BSP input is high impedance. I like the idea of using passive components better than active components. I drew the schematic of the circuit you describe. I would want to keep the PC input stereo, so I would have two sets of two 'PC' input resistors together.
Thanks again.
And, if anyone knows where I could get the plug that goes into the radio let me know. I don't want to cut the stock wiring. I want to be able to go back to stock if I choose too. Besides, it would be easier to make the circuit outside the car and then just plug it in.
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: C5 head unit 'mixer' or wire connectors? (NassauBlue)
It is easy to get a pigtail that has the HU connector on it from a stereo shop or Best Buy, but you will need to get the other sex connector + pigtail from a wrecked C5.
