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#295370 - 16/03/2007 00:43 Determining audio pinouts with shared ground?
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
I'm trying to integrate aux input to the stock amp on my sister's 1993 Volvo 240 wagon. The amp takes a 6 pin "DIN" input plug from the radio. Some Volvo forums unclearly report that the pins represent the positive wire of four speakers, a shared negative wire for the speakers, and remote amp turn on.

Any idea how I can determine which wires are which, or if this estimate is even correct? I tried a voltmeter to the radio's 6 pin output, assuming that adjusting the fade/balance to play through one speaker at a time would show signal only on that line. Unfortunately not so.

I grounded the voltmeter to the power/control harness ground and put the positive into each of the six pins, only getting signal on the center pin (supposedly the shared ground). Putting the voltmeter ground in the center pin and the positive on the others showed nothing.

Or could I used my hacked 1/8"-stereo-to-speaker-wire adapter to send input to the amp? Could I hurt anything by sending audio down the ground, amp sense line, or other weirdness?

No, I'm not integrating an empeg alongside the stock radio, sadly. I'm going to put a source switcher in for iPod aux in. I think it'll be a cool stealth install for my sister who doesn't care about audio quality; only wants to keep her brick totally stock.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#295371 - 18/03/2007 08:48 Re: Determining audio pinouts with shared ground? [Re: FireFox31]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
Quote:
I'm trying to integrate aux input to the stock amp on my sister's 1993 Volvo 240 wagon. The amp takes a 6 pin "DIN" input plug from the radio. Some Volvo forums unclearly report that the pins represent the positive wire of four speakers, a shared negative wire for the speakers, and remote amp turn on.



Sounds reasonable and jives with the adapter I found on a Swedish online shop, netonnet.se. See attachment - D6pin IN to 4 RCA+ remote.

Quote:

Any idea how I can determine which wires are which, or if this estimate is even correct? I tried a voltmeter to the radio's 6 pin output, assuming that adjusting the fade/balance to play through one speaker at a time would show signal only on that line. Unfortunately not so.



What setting on the meter? What was your signal? (Best bet would be a 0dB 50-60 Hz (power line frequency) test signal.

You should see a change in signal amplitude (voltage) by changing fader/balance...

Quote:

I grounded the voltmeter to the power/control harness ground and put the positive into each of the six pins, only getting signal on the center pin (supposedly the shared ground). Putting the voltmeter ground in the center pin and the positive on the others showed nothing.



Was it +12V? Then it's likely the remote... Might be that the shield (outer ring of the contact) is used for signal ground - did you try that?
Pure gut feeling - and a hope fore some sort of logic in the wiring - suggests the audio signals on the pins on the left and right of the symmetry-axis and remote on either of the 2 pins on the axis (center and the one below) and ground on either the remaining pin or the chassis (outer ring)


Quote:
Or could I used my hacked 1/8"-stereo-to-speaker-wire adapter to send input to the amp? Could I hurt anything by sending audio down the ground, amp sense line, or other weirdness?



Unlikely to hurt the amp, but possibly the signal source (connecting an output that expects a high impedance to a possibly low impedance input might blow the output due to excessive current.
I'd use a signal source that, worst case, I wouldn't mind tossing. Maybe an old Walkman...

Quote:

No, I'm not integrating an empeg alongside the stock radio, sadly. I'm going to put a source switcher in for iPod aux in. I think it'll be a cool stealth install for my sister who doesn't care about audio quality; only wants to keep her brick totally stock.


<Depending on how rushed you are I could try to take a look in some local shops, the 240 isn't exactly uncommon here (but I'm still not allowed to drive so it's a bit of a project getting around ).

But I'll see if I can find something more detailed online though.


Attachments
296067-240DIN-RCA.jpg (631 downloads)

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/Michael

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#295372 - 18/03/2007 11:53 Re: Determining audio pinouts with shared ground? [Re: mtempsch]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
Hey Mike, good to see you on the forums again!

Thanks for the tips, I will try these things. Yes, some other forums suggested the ground/ampsense are the center pin and one below, leaving audio as the "outside" four.

I had my voltmeter set at 12V to test. I got a 9V signal from the center pin and nothing from the others. My voltmeters only have ranges of OHM, DCV, DCA, ACV, so I thought DCV 12V was the only one to use.

I tried grounding to the outer ring, but I'm testing the female end of the connector, so I'm not sure where the contact is for that. I'll keep checking.

Thanks again, I'm sure this is possible.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#295373 - 18/03/2007 12:50 Re: Determining audio pinouts with shared ground? [Re: FireFox31]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
For picking out the remote wire 12V DC is right, but for the audio signals you want AC Voltage, not sure what level they might use - start high and step down while you don't see a signal.
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/Michael

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#295374 - 21/03/2007 01:04 Re: Determining audio pinouts with shared ground? [Re: mtempsch]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
Thanks for the help. A responder to my post at The12Volt forum suggested I use resistance to find ground. Low resistance between the - at a true ground and the + on a pin indicates that it's ground.

So, I should be set. Thanks for the help.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#295375 - 15/04/2007 01:09 Re: Determining audio pinouts with shared ground? [Re: FireFox31]
FireFox31
pooh-bah

Registered: 19/09/2002
Posts: 2491
Loc: East Coast, USA
I finally got to testing this out.

Resistance showed me the ground. Interestingly, when I turn the fader all the way in one direction, two audio lines decrease resistance like the ground wire. So now I know which are front and back.

Unfortunately, "AC V" and "DC A" settings on my unpowered analog voltmeter didn't show me anything coming out of the stock radio. With volume high or low, balance and fader centered or to one side, I saw nothing. What type of signal is line level output?

I guess I'll try hooking up headphones to the stock radio to find left and right. Or hook up an iPod to the stock amp.
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FireFox31
110gig MKIIa (30+80), Eutronix lights, 32 meg stacked RAM, Filener orange gel lens, Greenlights Lit Buttons green set

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#295376 - 15/04/2007 05:10 Re: Determining audio pinouts with shared ground? [Re: FireFox31]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
Quote:


Unfortunately, "AC V" and "DC A" settings on my unpowered analog voltmeter didn't show me anything coming out of the stock radio. With volume high or low, balance and fader centered or to one side, I saw nothing. What type of signal is line level output?



Sound shaped (i.e. AC), voltage (RMS or peak I don't recall) of between 1 and 8V depending on the radio (later/high end models often have the higher voltages as it allows one to run the amps on lower gain, reducing the influence of any noise picked up in the RCA wires (higher Signal/Moise ratio).

Of course, for a factory system most bets are off

Input resistance of amps are normally somewhere in the kOhm range so currents aren't very high.

You should get something on a low AC voltage setting (what's the lowest on your meter?), preferably having the volume on the radio turned up high and playing a steady test note.

What's the input resistance of the meter for voltage? If too low (unlikely, but with factory systems, who knows) it might overwhelm the current capacity of the output. Might want to try another meter, see if someone has one has one you could borrow - otherwise, new ones (digital) of OK quality (for general poking about activities) can be found quite cheap.

Unless of course the system does wacky stuff like only put outs the signal if it senses current draw on the remote or something like that. Never seen it, but factory systems...
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/Michael

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