I have been fiddling with my stock stereo for awhile now, I really like the factory head unit but the speakers suck. I found that if you replace the (2 ch volvo) amp in a 92 740 with a 4 ch (volvo) it activates the front door speakers makeing it a 6 speaker system (I just need 2 more speakers), no extra wiring needed just plug and go it is pre-wired! However, a few folks have mentioned that they have 940's with 8 speakers. I called the parts dept. and they say Volvo only makes 4 ch amps max and any extra speakers are powered by additional amps. Is this true? How do they split the signal to addtional run additional amps? Is there a splitter and what would the part number be? The Volvo parts guy was oblivious. I don't suppose anyone with one of the 940 8 speaker set-ups wants to take off their kick panel and snap a bunch of pictures of their amp and back of the head unit? This has been driving me nuts, there has to be a simple solution to adding additional (volvo) amps straight from the head unit.

Electronics knowledge says just put the two amps in parallel, you don't need a splitter, just some wire nuts. Wire each channel to both amps. But why do you want 8 speakers? It won't sound better than 6 or 4 unless you get better speakers, and if you do you wouldn't want to run the worse factory speakers at the same time. Ohh but more speakers more speakers grunt grunt, now I see where you're coming from. I'm putting in my new head unit next weekend, which has a 50-watt internal amp, but I'm going to try to feed the factory amp with its preamp outputs, so I'll be messing around with it plenty. Can't wait to see what I find, and I'd like to know anything you found about how the amp is wired, somewhere I heard only one set of speakers uses the amp but that sounds bogus. I may be able to help you out with the 940 8-spk info too, I'll check tomorrow.

Richard
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'90 744 tic

How many speakers do you have now? I can send you pictures of the 2ch and the 4ch amp. From what I see in my 760 the po bypassed the amp and wired the stereo direstly into the speaker wires (4speakers) I spliced the dash ones in when I bought it. Crutchfield sells a harness so you wire your new Head unit into the harness and then plug that into the OEM connector that was plugged into the back of your unit. The dash speakers are powered directly from the Hed unit so I am not sure how you'd work that.

I like the factory head unit it sounds really nice with better speakers, though the bass is off. I have speakers in the front doors, rear doors and in the dash. I wanted a little extra bass from a sub in the trunk hence the need for the extra output from an additional factory amp. I listen to classic rock, jazz and kids music. So I don't want/need the car next to me to get a head ache from the thumpin bass in my car, I just want what is missing from Phil Lesh's bass solo.

PS I have a wiring diagram for a 740 stereo. Let me know if you want it I'll zap it to you.

Hey Richard644,
Let me know how you make out. I have an 87 740t wagon and pulled my factory head unit out and saw the factory amp hookups and shoved it right back in its place. let me know how you wireset up goes, cause I'd like to put my Kenwood cd head unit in but I did not want to go into the wiring not knowing anything about it.
Thanks,
Rich

I ended up putting off installing my new head unit a couple weeks, but if you want to use the amp the key is having preamp (unamplified) outputs on the Kenwood. To connect it you'll have to connect to that DIN plugged into the factory head unit, or to bypass the amp you have to run speaker wire to the head unit. C is sending me a wiring diagram of the factory unit, could you figure it out with that?

Richard
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'90 744 tic

Your kenwood will power the speakers with out the amp. The amp is under the drivers knee panel and will have to be bypassed.