AudiWorld Forums - Bluetooth HF Car kit installed, with *true* phone sound through the TT stereo system

Well, folks, this was not easy, but doable. I have been searching for a decent TT hands free install for many years.
My own attempts ended in failure about 3 years ago.
I have looked at other installs, and I have seen what can be done. I knew that the sound could be well integrated in the stereo system but I also knew it would need some extensive modifications to make this work. I wanted to bypass as much of the TT's built-in phone wiring as possible to make this work, as it just was not reliable.
Also, the Audi OEM Audi car-phone system left a lot to be desired. They only routed the caller's sound through one of the front speakers. Other HF kits and install did not take advantage of the cars stereo system, at least, I have not seen or heard of one.

I did like that the `Concert' H/U supported `muting', and that the new, HF phone kits all supported this also.
With the recent release of `Bluetooth' for cell phones, and a former published `Bluetooth' install, using a Sony/Ericsson T616 cell phone, and the HCB-30 car adapter, I thought this could really work this time.
After going for about 3 years without a cell phone, I purchased the S/E T616 in December. Great phone, don't really use the camera, but I wanted it for a few main reasons; it had `Bluetooth' , there was a `Bluetooth' car kit, and it connected via `Bluetooth' to my 2 Macs, seamlessly.
I could up and download contact info. from address book flawlessly.
Also, picture transfer and ring tone transfer was a breeze, forget about web sites, just do it on the computer.

I spent about 4 hours today getting this connected into the TT.
Here is what I did. It was a lot of custom work.

I'm sorry for the set of incomplete pics, as most of them somehow vanished while downloading the best of them.

The components.
Here's what you get with the HCB-30 kit.
Mike, Switch on a cable, speaker, 'Black box' cables, etc.
If you used it right out of the box, the mike would amplify your voice, and the callers voice would come out of the speaker.
There is a wire that comes from the 'black box' to 'mute' the radio signal. It's basic wiring folks.

<img src="http://www.loomknitting.com/auditt/images/components.jpg">

Here's what I did.
First of all, what I did will not work with the OEM standard TT audio system, `Bose' or `non-Bose' without a lot of customization. It will work a lot easier with a custom audio install, with a new amp and speaker set-up.
I use a 5-chan amp and different speakers. I wired in 4 RCA cables from the back of the car, up to the H/U. The blue cable here in the second pic, and the `4-chan to Amp' circled in the pic. Normally, these get connected to the other RCA cables coming from the H/U, the circled' Head Unit out' area.
What I did was to add-in a relay board to create an `A/B' switch. When the relay is off, the signals pass from the H/U to the power amp. Stereo plays. I designed and etched this board. With me so far?

Next, I bought an inexpensive `Speaker Level to Line-Level' converter. Any decent car stereo place has this. Here's why this is needed. If you leave the HCB-30 in the stock mode, the callers voice will only come out of the speaker. In order to get the callers voice in to the car stereo, you need to take the signal going to the speaker, into the power amp. This is why I use a relay between the H/U and the power amp. But you cannot simply take the signal from the speaker wires into the power amp. It needs some sort of equalization and impedance matching. Hence the need for the `speaker-to-line-level' adapter. I also kept the stock speaker, and put it in the TT's dash. (See pic.) You need to keep the speaker, because it provides audio feedback to signal you on various parts of the `Bluetooth ` connections, like power on, volume changes, initial phone ring, etc.
See the speaker pic. It's pretty easy to feed the wires down through this area to where the H/U is.
Yes, that is hot-melt glue on the speaker grill.

<img src="http://www.loomknitting.com/auditt/images/dashspeaker.jpg">

The wires from the speaker that come from the HF `Black box' also then get connected to the low-level side of the `Speaker-Level to Line-level converter' box.
The output of this box goes to the Normally Closed set of relay contacts on my relay board. In order to trigger the relay, and switch the audio signals coming from the HF box into the stereo, the relay needs to `Sense' when the phone is answered.
This comes from the HCB-30 HF box. There is a wire from this box that goes to the `phone' signal input on the H/U. Problem is, this is a `ground' signal. You can take a grounded wire and put it on this pin on the H/U, and the stereo will stop playing, and in the H/U and in the instrument cluster, it will say `PHONE'. In order for the HF kit to trigger the relay on my board, I needed to add in a transistor (which is only a switch) to sense the ground signal, and trip the relay. In a sense, it's a switch to trip a relay. The signal coming from the HF kit black box cannot be used alone to set this relay.

Once a call comes in, the ring tone gets played through the small speaker, with the same increasing volume level that comes from how you have your phone set, and the same ring-tone that is set on the phone.
With a `Bluetooth' enabled phone, all I need to do is say `Answer', the mike picks up my command, answers the phone, and kicks in the `Bluetooth ` adapter, switches the audio signal from the speaker into the power amp in the car.
The mike is sensitive enough not to pick up and feedback the car audio.
The small `Bluetooth' switch on the left side of my instrument cluster controls the volume for the caller, where the mike is located. (I'm left handed, so it's easier there.) The switch also has manual controls for answering and hanging up the phone.
Here's a shot of the components, all wired up.

<img src="http://www.loomknitting.com/auditt/images/maincomponents.jpg">

Here is the switch and mike

<img src="http://www.loomknitting.com/auditt/images/switchmike.jpg">

<img src="http://www.loomknitting.com/auditt/images/ttphone1.jpg">

<img src="http://www.loomknitting.com/auditt/images/ttphone2.jpg">

Oh, and one caveat;

If you use run an after-market amp and speakers, but you use the signal from the H/U to remotely turn on the power amp, you will run into a problem here. When the mute signal is present on the `phone' pin on the H/U, it also cuts the power to this remote-amp turn-on pin. Another reason not to use the Audi OEM system here. They did not ever plan to send the phone audio through the sound system. I had to find a new ignition-on wire to remotely turn on my power amp. This has a negative effect on the "Ignition-off" radio button. This now no longer works.