Tube Love

This isn't really about tubes but it is definitely part of my quest for good sound on the cheap.

I went on my first real adventure in car audio when I installed a pair of vintage 12" tri-axial EV speakers into my '66 Barracuda last summer, but that's a story for another time...

Back to our hero:

My wife and I just purchased 2 used Saab 900's, and I have been busily pimping both rides on my lunch hour and after dinner.

Part of our buying spree (btw: just so no-one thinks we're rich or anything, we actually saved a bunch of money by buying 2 high-mile 90's Saabs - spending 1/2 of what we had budgeted for a new Mazda3, and I'm pretty sure we both got much better cars as a result plus lower payments and insurance...) involved the purchase of a pair of iPods.

The simplest in-car iPod solution is, of course, to go out and buy a $99-140 head unit with an Aux In jack in front, plus a 1/8" stereo cable to hook the iPod to the jack through it's headphone output. Which is what I did for my own car at first, while my wife used a cassette adapter with her factory radio.

I borrowed her car, and I really liked the sound and adjustability of her factory Clarion cassette/radio. It also integrates nicely with the dash (of course) and the SID (System Information Display). The sound is decent, with tight low end and reasonable highs with surprisingly good imaging even though the door speakers are not installed in her car. But the iPod via cassette adapter interface was significantly bad, and in examining the cassette adapter it was obvious the record head was worn and grungy and something was peeling off... also, it's possible the ipod's headphone output doesn't send a strong enough signal (argument towards the Belkin car-lighter adapter).

So she was getting alternately awesome sound when she listened to the radio and crappy tinny sound when she used her iPod. No wonder she kept leaving the ipod home!

I've never liked the whole cassette adapter thing - it seems like such a primitive way to transmit audio: e.g. send it through 2 sets of magnetic heads that are pressed together while a motor whirs away doing nothing. Assuming you get good contact between the tape heads and adapter you can get decent sound. But tape decks are finicky creatures at best. A lot of variables can affect the sound: the way the tape blank is inserted in the deck, are the play heads in the right place, is everything clean... lots of places to degrade the heck out of the signal. ... or maybe it'll add some of that "tape warmth" everyone's gotta have... I'll follow up on that tangent later.

Anyways, I went down the easy path and bought a mid-level Sony head-unit with Aux In on the face and off I went. Within a day I realized the sound in my car was somewhat anemic compared to my wife's car. So I added an Alpine amplifier and a 10" subwoofer in the trunk. Wow! Huge difference, but still something was missing. My door speakers weren't working, the amp to run them is gone. So I ordered a factory head unit off eBay and a slave amp for the door speakers.

Now, there is no Aux In on the factory Clarion cassette radio for 93-98 Saab 900's, but there IS a 13 pin DIN-type CD Changer jack in the rear of the Saab head unit.

It's called a "c-bus" interface and it looks like this (round one on the left - the rectangular ones are the main harness):


Here's the pinout:



(image from: http://www.mictronics.de/?page=cdc_proto#Clarion)

There's also a round output on the side to connect it to a booster amp for the door speakers. I found the amp on eBay but I still need to find (or make) the right cable to connect it to the head unit.


I've found it difficult to source the main head-unit after-market harness anywhere but the specific Saab aftermarket. This seems weird as I'm pretty sure it's the same thing that came in a lot of GM's at the time. Will investigate further (would be nice to have a handy nearby junkyard).

After 1998 they went with a new architecture called ceNet or something which has a square connector (also 13-pin I believe) and it does computer stuff.

Clarion makes an adapter for $100 which lets you run an old C-bus CD Changer with a new ceNet head-unit, but not vicey versy. There is surely some obscure legal or marketing or just plain ornery reason they're not making an adaptor that lets you just use your old c-bus head-unit with an iPod (or new CD-Changer - as-if) but for the life of me I can't figure it out. Just about every other auto maker in the Universe has a product available on the aftermarket for $59-$99. I think it has to do with the juggling leadership of of GM/Saab/Chrysler/Daimler/Benz - but somewhere in there the 1994-1998 head units got orphaned. I also suspect that "cbus" being a proprietary protocol has something to do with it.

I've searched the internet high and low, using the terms in the title of this post, and more, with very little luck. One guy soldered wires to the circuit board of his factory CD head unit but it requires you to have a blank CD running all the time (whirrrrr). He to0ok just the audio signal off the board, none of the control info. Various similar approaches here:

http://www.saabnet.com/tsn/bb/NG900/index.html?bid=63425

This guy here describes building a cable by taking apart a Belkin adapter:

http://www.mindspring.com/~pmbenn/iPod/cable.htm

The only good solution, as far as I am concerned, would be a cable with a c-bus DIN connector at one end, and an iPod data/power cable at the other. Switch the head unit to to CD changer mode, and you're listening tothe iPod. If necessary, stick a gronker in the middle to fake out the head unit - sending a certain voltage down a wire or whatever. How hard could it be?

Stay tuned to find out!!!

Update: Sunday, May 28, with actual sunshine

Okay, so now I have lots of wires and an extra head unit and a free afternoon...

let's see if I can cook something up...

http://www.mitt-eget.com/saab/faq_electrical.shtml (good info for fixing the SID's, later)

CD Changer NG900 FAQ

I went to Best Buy and picked up an adaptor for a Kenwood stereo, since it also uses a 13-pin din connector. Then I found this on the internet:

http://nodivisions.com/tech/kenwood_aux_adapter/

This guy is hooking up a Kenwood head unit to an iPod. He wires up the 3 audio leads to RCAs then puts a 10K resistor across pins 3 and 9 and this fools the Kenwood into thinking the CD changer is running. Then you send it iPod audio through the RCAs.

Here's some more info, from a VW :

Connect pins 5 and 9 together via a switch (on, means a logical +12V signal appears on the 'slave on' pin hence switching the head unit over to CBus input as it thinks a CD changer mag is present).Then simply connect the Left, right and gnd pins to the appropriate RCA's and you should have yourself one CBus - RCA converter for clarion.

So now I'm hoping a similar trick will work for my Clarion. But since a $20 adaptor already doesn't exist for this application, methinks there's maybe a reason: e.g. I'll need to send some sort of data down the wire and a little resistor magic just ain't gonna do the trick. Maybe it'll need to be a real extra-shiny gronker to be able to fake the Clarion out...

(later)

This guy is definitely onto something, but his solution seems to require you to have an actual CD changer running all the time:

http://users.adelphia.net/~jlehome/aux_input.htm

Update 4/25/2007: Well it turns out the CBUS option won't work (for me anyways) because it requires data to be sent down the wire. I suppose if I had a CD changer available and TONS of spare time I could try to intercept the data, figure out what it is, and build a gronker to fake out the headunit... instead I am going this direction:

http://photo.platonoff.com/Auto/20060924.Saab_NG900_Line_Input/

(very nice step-by-step instructions for adding a line input by soldering a connection internally to the tape connections, then using a switch on the tape door to enable/disable)

Crookes Y Tube:


















http://www.arcsandsparks.com/ytube.html