Question for Television (and any other electronic guru's)

[RobWheatley]

Hi Malcolm
Just wanted to pick your brains, not mercedes related but it is ICE related.
Mods can move this if its in the wrong place as I didn't know where to post it.
I am trying to connect a car stereo (bluetooth & MP3) to a motorcycle intercom on my BMW K1100LT, the stereo output (for the front channel) has 4 wires, 2 for left and two for the right channel (+ & -) there are no phono outputs for an amp, the intercom only has three wires for the input (mini jack plug to take iPod's) I have tried different configurations to connect it, putting the two negatives toghether, using a ground from the stereo but it either sounds muted or distorted.
Is there any way to alter the output to 3 wire or to make some kind on interface that will enable me to do this.

The reason for asking is so that I can alter the volume and mute it when needed (safely of course) and to save having to have my iPhone plugged into the intercom all the time.

Thanks in advance if you can help.

Rob

 

[Miffy]

the combination of using FL Fr and common earth should be fine, you just need to check you have the 3.5mm pin wired up correctly. You will need to ensure you keep the stereo volume kept to a minimum as it may blow the inputs on your Bike kit.

I think the normal configuration is tip audio, 1st collar audio, 2nd collar ground, 3rd collar if present unused.

 

[cleverdicky]

One thing to consider is your intercom will be mono a single channel, while your stereo output your trying to connect is 2 channel.
The stereo (speaker ) output voltage will be far to high under normal use as an input. It can be done easy enough. You need a small converter to take a sample of your stereo output and convert to a mono line level output.
I have seen such devices, nothing special, but a bit of hunting around will be needed.
try the usual maplin, cpc, farnel and rapid but also Keen electronic and ebay etc.
You'll find one.

 

[cleverdicky]

Here ya go. Two mins on google.
An ebay version.
http://www.ebay.co.uk/itm/RADIO-DES...o_Audio_Parts_Accessories&hash=item35c08df8eb

Info here if you are handy with a soldering iron and a few resistors.
http://marcusmorris.blogspot.co.uk/2010/04/stereo-to-mono-converter-how-to-do-it.html
Or a posh one.
http://www.palmer-germany.com/pro/en/PLI-06-Line-Level-Converter-2-In-1-Out-PLI06.htm

Sure there are plenty more out there.

 

[television]

If the sound is distorted it could be that the input is too high for the device that you are plugging into, a resistor in each channel wire could solve it, try about 4.7k in each leg and these could then be joined together to give a mono output without upsetting the stereo part.

 

[RobWheatley]

Hi All
Thanks for the replies.
I have had a look at the links but they are for stereo to mono, the intercom is stereo input not mono, I think it is a "balanced input" where as the Stereo unit is an "unbalance output"
When I used the two + outputs together with a earth from the case of the radio one side was ok but the other side was very muted and distorted.
If I joined the two grounds and used that it went mono with no volume.
From what I have read I think it is because the intercom is expecting a balanced input (with a ground, hot line and cold line) but it is getting a ground and two hot lines and rejecting one of them.

I have found this page http://www.fivefish.net/diy/balanced/default.htm
But this is for pre amp line levels (and only one input) where as the output/input are already amplified.

 

[cleverdicky]

If you just stick the two outputs together, they will cancel out and do what you said.
Forget the 'balanced' part. Its just confusing the issue.
Use a good multi meter and turn up the volume. Connect one leg to the ground speaker wire, the other to +, you should see a few volts, make sure meter is on AC. Keep the same ground and try the other +. This should confirm if your outputs are the same way, or phase. It could be your out puts are not the same way round. You will get a noise from each channel but if they are not the same, one will cancel out the other.

If you have a stereo input thats great. You just need to dumb down the levels to a suitable amount. Which is why its distorted.
You can simply use a 5 -10k resister. You will have to experiment to find the best value. Or as i said before buy a proper converter for a few quid.

 

[television]

The normal way to convert a stereo to mono line is to put 2 suitable resistors say 4.7kΩ in series with each lead, but they will need a terminating resistor as well wired from the ends of the 4.7kΩ resistors to ground, and a suitable value would be one matching the input of the device where they will be plugged in.

There is no loss in doing this, the 4.7kΩ may need to be increased,,its hard to say without playing my self.

 

[The Pan Man]

Autocom all the way. When instructing had Music Mp3, Phone (A must have when instructing), Sat Nav and Intercom all driven off the same kit fitted to Pan Europeans 3 of them 1100 x 2 1300 x1, BMW R1150 GS and a GSA + FJR 1300 and ZZR1400 all with no problems. Swopped the lot on to my last Triumph Tiger in about 1/2 hour including making up longer / shorter looms where needed. I understand now that you can do all this with Bluetooth / Wireless. If stuck phone or e-mail Autocom always very helpful, a lot of bikers used to work there. Hope this helps. Oh yes before settling with the Autocom set up I tried several other makes that claimed all and delivered nothing at all, a lot of refunds all paid no problems just a lot of my time.

 

[RobWheatley]

Thanks all, will try it out tonight if I can and post back.

Pan man
The intercom is an autocom, I can plug my mp3 sat nav and phone into it no problems but want to be able to feed the stereo into it as well (radio/CD/MP3 & bluetooth) that is where I am having the problems.

 

[The Pan Man]

3.5mm Y Connector on the Mp3 lead, just a thought.

 

[The Pan Man]

Rob, The tech side is over my head but my set up was definatley stereo out of the Mp3 side and mono on the sat nav and phone. This was back in 2001 / 2002 before the wireless and bluetooth autocom units were out. I still have a bag of bits including 2 of the splitter boxes and more wires than you can shake a stick at. From memory the Autocom unit feeds in to one splitter either all black or black and red then the second splitter is used to feed the sat nav and Mp3. With the Vox set correctly (Yes I know it's difficult for European tours) speaking canncels everything if you are using the intercom or phone. Be interested to see how you get on.

 

[RobWheatley]

Just an update.

Think I have got it sorted out now, changed the stereo for one with RCA outputs, not tried it yet but did hook a standard set of headphones up to it and they worked in stereo with no distortion (allbeit a little quiet but there is gain on the intercom)

Need to get a twin Phono to 3.5 Jack lead (maplins) to feed it into the intercom to try it.
I will keep the speakers connected but will put a switch in the leads so I can turn the speakers on and off as needed, if its just in town I can use the speakers and hear it rather than the head set speakers.

If it all works I can use the bluetooth audio from my phone but I can keep it safe and dry in my pocket.

Thanks for the help.
Rob