Wiring 'Aux-in' (iPod) connectors to Car radios

[Newshound68]

Meant to add: the Bluetooth device is charged by a usb to computer externally at the moment. Surely it could be wired to take voltage from the radio? But how to step down?

For my motorcycle radio when I want to listen to my iPod I use a bluetooth adaptor such as http://www.ebay.co.uk/sch/i.html?_fr...r+NEW&_sacat=0 . Wires are a bit of a hassle on a motorcycle!

[Newshound68]

Yes I've got something similar.
What I mean is, can you power the dongle from the radio itself by opening it up?

['LIVEWIRE?']

By adding a 7805 Regulator IC, which can be mounted inside the radio, a +5v DC supply can be provided from which the Dongle can be powered. A suitable USB cable can be modified to connect this to the radio.

[2009poolesparky]

Can you clarify which terminals I need to attach the aux lead to on a Motorola 112 radio, as I am new to the radio scene and don't quite understand exactly what is meant in the original posting. Thank you

Alex

['LIVEWIRE?']

Remove the connection from the volume control 'hot' side (apologies for the use of American Terminology, but I don't know of another way to dufferentiate between the signal and earth terminals). Connect this lead to one of the two leads coming from the 'aux-in' (I use 3.5mm stereo jack sockets for this purpiose), then connect the other to the volume control. Since devices such as MP3 Players, IPods, etc., are stereo and the 112 is Mono, the two channels need to be joined via series resistors of about 1k. The first two illustrations in my original post should show what is involved, and there are other 'sticky' threads explaining the need for the series resistors.

[crackle]

There are 3 tags together on the volume control. The "hot" tag or terminal is one of the outer tags on the volume control and can be identified by touching it with a metal object, you should hear a buzz which will increase as you turn the volume up. The earth return from the aux in connects to the other end of the 3 terminals on the volume control.
I hope that helps.
Mike

['LIVEWIRE?']

I didn't think to explain it like that, Mike. I guess it's because, having worked with such radios for over 40 years, it's second nature to me, but not so to those unfamiliar with these things. Another tip - when looking at the volume contol from the rear, the 'hot' terminal is always the one on the right hand side.

[julie_m]

I usually refer to the terminals of a potentiometer with the highly imaginative names of "anticlockwise end", "slider" and "clockwise end".

But then, I was always good at those puzzles with the blue sphere and the red cube .....

[2009poolesparky]

I have been told to connect the two new input wires (from the aux cable) together and then I will have the screen cable.

Also I need a resistor in series, but what value?

Here is a photo of the volume control looking from the bottom. Does the screen cable join on the terminal with the pinky/ orange wire on the right hand side?
With the red and white aux in cables onto the terminal where the White cable is connected?

Thanks

['LIVEWIRE?']

Disconnect the white wire from the tag on the volume control nearest to the push button tuner, but do not disconnect the capacitor wired across the two outer tags of the v/c. If you are not planning to listen to the radio, the white wire can simply be removed from the PCB and no further connection made to the board, but if you want to continue to hear radio programmes, either a changeover switch or switched jack socket is needed, wired as described in my earlier posts on this subject. As to the resistors, any value between 1 and 10k will be OK. Two resistors are needed, one connected to each of the inner cores of the lead from the 'aux' input, i.e. one to the LH Channel lead and one to the RH Channel lead. The 'free' ends of the two resistors are then joined together and connected to the tag on the volume control from which you removed the lead. The screen of the 'aux-in' lead does indeed go to the 'cold'(earthy) side of the volume control, which is the one to which the orange lead is connected.

[2009poolesparky]

Excellent that is much easier, thanks for your help. I am just planning to listen to the aux input, so will remove the White cable as you suggested. One final question.
He speaker output on my radio only has cable for one speaker. Is there a way to add another speaker so I can have two?

Thanks
Alex

['LIVEWIRE?']

AFAIK, the Motorola 112/114/122/124 series can drive two speakers in parallel. I have the service manual somewhere, but not immediately to hand. It may be available for £1.99 from the VRSD link at the top RH side of this page, and will confirm or refute this. Be aware that the output will still only be monophonic and that connecting too low impedance speaker(s) will damage the output transistors. The nominal impedance of car speakers is 4 ohms. Back in the day (1970s) if two speakers were fitted in a car, they were often wired via a speaker balance control though these are unlikely to be available now.

[PaulR]

I have had one driving two speakers in my Rover P4 for many years with no problem. It seems a shame to disconnect the radio stage permanently.

['LIVEWIRE?']

Originally Posted by PaulR

It seems a shame to disconnect the radio stage permanently.

Fair enough, Paul. As to disconnecting the radio stage, it only, in the case of the Motorola 112, etc., involves removing one short length of wire betwen the PCB & Volume Control, which is easily replaced if needed. Other AM Mono Radios such as most Radiomobiles, earlier Motorolas, etc, are similarly wired,

[2009poolesparky]

Thanks for your replies, what would be the best resistance speakers to fit to give the best sound? The louder the better really. As for disconnecting the radio signal, my car doesn't have an aerial and I don't know how many stations still broadcast on MW/LW in the UK.

['LIVEWIRE?']

(Almost)all Car radio Speakers are 4 ohms in any case, so two 4 ohm speakers in parallel should be OK. Bear in mind that the output power of that Motorola amplifier (and indeed most others of that era) is, at most, 6 watts RMS into 4 ohms, so don't expect modern 'HiFi Performance from it, though the sound quality into a pair ofspeakers should be good.
AS to AM Broadcasting in the UK, on MW there is/are BBC R5 Live, Talksport, Absolute Radio, and, in some areas, local or regional stations. On LW, BBC R4 is the only UK station, but RTE R1 on 252kHz is usually a good signal, as are Europe#1. RTL (in French), and France on 182kHz.

[2009poolesparky]

Ok that sounds easy enough. In theory then I can solder another speaker cable to the two terminals inside the radio, where the existing speaker cable is connected?

['LIVEWIRE?']

An exra length of twin flex could be soldered to the connecting points inside the radio, but this isn't strictly neccesary. Two speakers can simply be connected in parallel via suitable lengths of flex, then connected to the exsisting speaker lead fitted to the radio. If this lead still has the original 2-pole socket(many get cut off), and you have a lead terminated in the matching plug, simply join this to the wires going to each speaker. As to speaker phasing, given that the original plugs & sockets are reversible, and most speaker flex has a strip on one of the two conductors, simply ensure that the two leads are connected together 'like for like' i.e. striped lead to striped lead. No harm will come to either the radio ior the speakers if they are wired out of phase, but a reduction in bass response will almost certainly be noticed.

[Tiggers]

An attractive feature in my car is the original Smiths Radiomobile radio fitted by Henlys when new, and the appearance and sound quality is very good despite being a LW
/ MW only unit. Unfortunately, there are nowadays nearly no radio stations worth listening to still broadcasting on MW/LW. I did not want to go down the route of converting to negative earth and fitting a modern stereo, and wanted to retain the original unit and sound quality. The solution is what is known as a ‘wired modulator’ and there are a few variants available in the marketplace, but the one I have settled on is the Redirad, designed and manufactured in the US. What this does is connect iphone, mp3 player, smartphone, CD player, whatever makes sound and has a 3.5mm
output socket, directly to the original radio via the antenna lead. The unit is small (a little larger than a pack of playing cards) light, and easy to connect. The case seems
sturdy, and the wires, particularly the antenna male & female leads are of a very good quality. Instructions are clear, and adapters to allow connection to existing fused
power supply are included. The power and earth wires around 5 feet long, the 3.5mm jack lead is around 6 feet long, although the antenna connectors are short, it is designed to be located near where the antenna leads enters the radio itself. I did find also a short series of videos on youtube showing one of these being fitted to a 1980’s BMW (FM version). The only difficulty if there is one, and this will vary from car to car, is the routing of wires etc. The unit is designed for the very widely used ‘Motorola’ type
aerial lead connectors, but adaptors are widely available online for around £5 if your car or radio is fitted with a different set up.

Unplug radio antenna from radio.
Plug RediRad into Radio antenna socket.
Plug Antenna lead into RediRad.
Electrical connection is one to an ignition controlled power supply, and to earth.

That’s it, and you are left with a lead (with a 3.5mm jack) to plug into whatever you would like to play. I have placed the unit in my car behind the facia just on top of the radio itself, secured with cable ties (again included in the pack). Connect up the player, and tune in on the radio to 1000KHz (the ‘10’ position on some radios, or 300 metres.) I
have tried an mp3 player, Nokia smartphone and an iphone, and all work fine.

Available for positive & negative earth cars, 6 or 12v, and there is an FM version for cars fitted with FM radio. The sound quality is as good as the radio amp & speaker, and I
like the tone of modern music on my cars single 6” speaker. Not just for music; plug in your smartphone and you have effectively got a hands free installation, (and in my car
the unused ashtray is the perfect cradle for a phone) with the inbound call being heard through the radio speaker(s), as you would with a modern hands free system, and if you
want to use the satnav on a phone, again, it will play through the radio.