Modifying the AD185M head unit...

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Modifying the AD185M head unit...

Weekend driver

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Joined
Feb 26, 2003
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London, United Kingdom.
Until I get a new head unit (still trying to decide quite what!) and wanting to use four speakers in my Marea Weekend... Does anyone have the knowledge (or luck) to tell me how to change the normally two-channel AD185M (basic head unit) to four channels? The handbook says have it done by a Fiat Dealership, but I'm OK with a screwdriver and soldering iron and all I need is the information.

I know that you can just remove the adaptor in the lead to the head unit, but that does not allow the fader option to engage, and the front and rear speakers would be antiphased (loss of bass overall and possible weird directional effects at high frequencies!). I want to do this properly.

There are probably jumpers on the board inside the unit that need to be moved, or links to be desoldered and remade... Any ideas - all help gratefully received.


Have a good Weekend!
 

2.0 20v

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May 28, 2002
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Hampshire (London way), United Kingdom.
The block of speaker terminals thats plugs into the back of the headunit has the space to add the connections/speaker wire for the rear speakers. This could be done quite easily.
But are you saying that if you did this you wouldn't be able to use the fader?
Do you know if that model of headunit is used in other Marea models with 4 speakers?

Si.
2.0 20v HGT + Superchip + NOS (soon)
 
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Weekend driver

New member
Joined
Feb 26, 2003
Messages
58
Location
London, United Kingdom.
The connectors are on the back of the head unit, the wiring is in place for the rear speakers (as standard) - though the rear speakers are yet to be fitted (I reckon on the JBL 87mm co-axials). The fronts will probably be replaced by the JBL 7x5's with the JBL tweeters in the dash...

The head unit obviously contains two pairs of power amps, which are set in the two-channel mode as a pair of bridged pairs, fed by a phase-splitter. In the four-channel mode, each of the power amps works individually from the front/rear fader-controlled signals.

There is probably some arrangement inside the head unit that would change the set-up from two-channel to four-channel, and this is the information I seek... Anybody know quite how? I don't know the Fiat range well enough to know if the AD185M is used in other cars...


Have a good Weekend!
 
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