Stereo/DVD: SC-xxx AUX INPUT HACK

[jcwacky]

Originally Posted by bobbych

I did the 605 months ago and can't remember off the top of my head where the points were I do know it was on the tape deck though. The unit is not the best for this hack but it can be done Sorry I can't offer more assistance but I don't have one in front of me to test

Cheers bobby, I ordered some 10uF 25V capacitors off ebay a few days ago in anticipation, and I've identified a left and right on the tape deck. Shame there isn't a known run detection point like on the 801, I'll just have to try and find a blank tape!

I'll take some pics and post how I get on in case anyone else is curious.

[bobbych]

i have spent hours probing the 605, and there is no way to fool the tape deck. I originally thought the same with the 805, but i found it in the end, but alas, not with the 605

[jcwacky]

It works!!! I've successfully applied this hack to the HU-605!

Here's my tale, hopefully it will help others trying this.

Taking apart the radio was more tricky than I'd expected, lots of screws (about 30) to take out. Luckily they are all of the same type (apart from 2) so no worries about having to log which screw came out which hole!

Eventually got the bottom open, and located the cassette deck and PCB marked with left and right points.

First a soldered a short wire to each point, and prepared my stereo cable. I used a male 3.5mm jack to male phono's as it's the best I had about. Cut the 2 phono's off, stripped back the cable to give me the left and right channel wires, along with their earths. Soldered both earths together.

Luckily I found a small cable from an old Xbox chip which had a washer type piece attached, this worked perfectly to connect my joined earths to a screw. The piece isn't required, you can just use a normal wire to connect it to a screw.

So here is what it looked like now:



Next I needed to add the capacitors, I'd ordered some 25V 10uF capacitors from ebay, and soldered them on, with the positive leading to the tape deck and the negative to the cable:



Added some insulation:



And that was it! Or was is?....

I slotted the unit back together but didn't bother screwing it up as I wished to test it first, so went out and stuck it in the car... the head unit refused to on pressing the on button did nothing. So brought it back in and screwed up a few bits which pulled the unit together a bit more... bingo it worked! (I don't think the fascia was connected properly first time, the screws helped it.)

But then I was faced with it asking for the radio code! I've only had a the car for a few weeks, so checked through the manual and service history book, but no code in sight. Luckily a short call to my friendly Volvo garage later, I had the code!

So I plugged in my iPhone, with a blank cassette in the deck and bingo it worked, and sounded great! Ran a channel test MP3, and was glad to hear that I was getting stereo, but not so happy to hear the left and right the wrong way round!!

I took the unit apart again and swapped over the L and R wires, still don't know why they were the wrong way round, perhaps the stereo cable I was using was mixed up. So 1 more test confirmed I now had the channels round the right way.

So I screwed it all up, (manged to do so without any spare screws!) and went back out for the final fitting. Now I basically had a 1.5 meter cable coming out the back of the head unit, with a 3.5mm jack at the end, I did this because I didn't want cables running down the front of my dash, so threaded the cable round the back of the dash and out through the glove box! (Removed the little glove box shelf, pulled the cable through then screwed the shelf back on). Now I can just open my glove box, grab the cable and plug it straight into my iPhone etc.

So at this point everything was working great.

Interference Problems

I then preceded to test my new setup with my TomTom iPhone car kit, the car kit basically plugs into the cigarette socket to charge the phone, it also has a 3.5mm line out. Upon connecting my stereo cable to the line out and playing the iPod on my iPhone I was immediately disappointed how distorted to audio was. It works a bit better when I just connect it direct to the iPhone when it's in the dock, but there is still lots of interference in the audio, as soon as I disconnect the dock it goes away.

I tested the dock inside my house on some speakers and it provided crystal clear audio, so there's not a problem with it.

The only other thing I have to do is work out the quietest way to play a tape in the car! Any suggestions?

Sorry, this appears to have turned into quite an essay! Hopefully it will help others out.


EDIT: With a bit more research and testing, here's what I've found:

The TomTom car kit output works as a line out, and therefore outputs at 100% volume which is what causes the distortion on both on my aux input and a cassette adapter, so I'm not expected to be able to fix this.

When just connecting the audio directly to the iPhone's headphone socket, it sounds great! But only if the phone is not in the TomTom dock. If the phone is in the dock and the dock is plugged in to the cigarette socket, then the audio sounds fine, it's not distorted, but there is some interference introduced, starting the ignition makes this interference worse by added a high pitched noise to it. As soon as I remove the iPhone from the dock, or unplug the dock's power, the interference vanishes. As above, this interference does not happen when using the dock in my house. The interference also isn't there when I use a cassette adapter as opposed to my custom input, even with the TomTom dock.

So to summarise this issue: The combination of my custom input + my car + tomtom car kit cause this interference.
Substituting the car, for speakers in my house = no interference
Substituting my custom input with a cassette adapter = no interference
Unplugging TomTom car kit and just using iPhone = no interference

Interference noise (engine off)
Interference noise (engine started)

So why is my input subject to this interference, anything I can do to shield it?

[bobbych]

nice read, and glad it sort of worked. I found with my earlier attempts, is that you will, get some feeback, hiss, noise etc from the tape. This is why i strived to find a hack which removed the tape deck from the system and wired the hack directly to the main board, and not the cassette board.

But as you know, i have not managed this on the 605, only the 700/800/801/802 and 805 models

But, when i did the hack on the 605, and used a tape, i did use a Line out, from my ipod car kit, and i noticed no noticable noises other than some tape hiss

[jcwacky]

Originally Posted by bobbych

you will, get some feeback, hiss, noise etc from the tape.

That's the thing, I don't think it's coming from the tape, because it works fine if I unplug the TomTom car kit.

Since my post, I came across some ferrite clips, I've added a couple to my cable and these have reduced the volume of the interference a bit, so it's now usable. Would be nice to get rid of it completely though.

[jcwacky]

Interference eradicated!!

So I found some info on the TomTom website about interference when using the car kit. They called it "ground loop noise" and recommended Griffin's Noise-reducing Audio Cable.

I did some further research and discovered that this was the interference I was getting, and the high pitched interference that I got when the engine was running is called "alternator whine".

They occur when the iPhone/iPod is being earthed at 2 different points, once through the audio system, and once through charging system. I tested it using a standard iPhone car charger instead of the TomTom car kit, and had exactly the same interference.

So I purchased Griffin's cable (iLounge review), connected it to my existing cable, and boom, all the interference had completely gone! The sound quality is now great!

[doodlebug]

Just wanted to thank bobbych for this excellent thread.

I took the plunge and decided to do the hack on my SC805. Firstly I tried adding the connections to the cassette deck, but found that the sound produced was all distored and by no means clear (almost unlistenable <- is that even a word???), so I took it out.

Then I followed the instructions for the SC802 (as per this page). Soldered on to the bottom board, added the capacitors, connected it all up and the sound is crystal clear. To fool the tape deck, i took all the tape out of an old cassette, and the little spring thing in the cassette that tape floats over, inserted it, and glued the deck shut. I personally cannot hear the tape mechanism working at all, even with the volume turned right down. I can even take calls on my iphone via the HU, and it comes through the speakers!!!!!

This is a quality mod, well worth 1/2hr of my time. My soldering skills leave a lot to be desired, but this was no problem to add at all.

Thanks bobbych
Neil

[bobbych]

Neil, so glad it worked for you mate.

Watch this space, a member is sending me his 805 this week. I will find a way to Mod the Tape deck, so you can remove it.

The 802 is very similar to the 802, just without the CD, so it will prob be do-able. If so i will post a thread for you to follow, then you can remove the tape altogether

[RRM]

The aux-in solder trick worked fantastic for a couple of days on my SC-801. But now it is completely quiet.

Has anyone had the same experience and suggestions?

[bobbych]

is this a hack you did, or did I do it for you?