# Alpine 7909 Audio board upgrade



## jeffp (Jan 18, 2015)

I have been working on the alpine units and have com across a unit that has some interesting modifications. The first modification is turning the AM radio into an aux input. So when you select the AM it reverts to the aux rca input out the back of the radio. This was an additional rca connector left and right.

The second modification is very interesting. The weakest point in the 7909 audio amplification of the signal is at the audio board. The stage that is sent to the bass and treble section creates all of the distortion in the final output rca line out cable. 
Have you noticed when you enable the CDS the signal out of the deck is clean with the volume control all the way up, but when you turn on the bass/treble stage, by turning off the CDS the signal becomes distorted. 
The modification changes out the op amp (dual) with the OPA627 op amps. they are single op amps, and you can buy a daughter board with two amps to solder in place of the old part. Here is the link to the part, a bit pricy, but the opa627 part is not cheap like the majority of the op amps out there and for good reason.
More Information Page
This modification cleans up all of the distortion in the audio stage, so the final line out audio is very clean. 
cool upgrade, I can wait to get my parts, aside from the one I already have.


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## qwank (Aug 4, 2013)

why is there an additional aux input on these? no one can seem to answer me on how it works. if there is a changer in, what is the aux in for and how do you get it to work?


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## jeffp (Jan 18, 2015)

the aux input is for a audio input from a different source. Most people don't use the aux input, it is enabled with a wire from the power harness.


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## qwank (Aug 4, 2013)

which wire enables it? and do you ground the wire or add power to it? I would like to use the aux in on mine. This is a J model if it makes a difference. Thanks


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## jeffp (Jan 18, 2015)

I had to check the wire first. 
So there are two Blue/White wires. If you have the stock wire harness then it is the blue/white wire on the first 4 pin molex connector. You apply a momentary 12 volts to the wire, that will enable the AUX input RCA connectors. The front panel will say PAU, the cd player, or radio will stop playing and the aux RCA's are live. The wire designation on the schematic is REMIN or remote in. 
The thing to keep in mind is that with the AUX input, you DO NOT have volume control of the radio, so whatever you are playing the audio from controls the volume through the 7909.

You do not have to keep 12 volts applied to the wire to stay in the remote operation with the AUX inputs. So when you want to turn it off you push the radio or cd play buttons and the radio will return to normal operation.

Now, if you want to have the radio with the AUX input and volume control, there is a way to do that also, but it does require some modifications to the unit.
So here is my idea, Since most external inputs use the micro jack, it would be the best part to build and use make the switching circuit with. You will be able to run the 12 volts to switch a micro relay and then just run the audio left and right channels. Then the only thing you would need to do is to select either the am function, or the FM function to pass through the Audio. Then you have the volume control just like always. 
I believe that is very possible to accomplish.

Hope that helps.

Oh and also since I did not get much response. I have a setup that will run Bluetooth from all of the apple devices, and aux input also, and from your phone, talk on the phone, and listen to music through the phone as well. Basically all of the new bells and whistles all the new cars have today.

REGARDS:

Jeff Priddy


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## qwank (Aug 4, 2013)

Thanks, I don't have the original harness so I'll have to figure out which one it is. I'm guessing you meant white/blue since there are two of those and blue/white is remote turn on. Any idea what the other white/blue wire does?


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## jeffp (Jan 18, 2015)

The blue/white wire is the correct wire to use. 
On the 12 pin connector. You have the lightblue/white wire= remote anp turn on then next to that you have the darkblue/white wire=aux switch for the aux rca's Next to that you have the white/blue wire=display dimmer


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## qwank (Aug 4, 2013)

thanks, man


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## an2ny888 (Jun 27, 2008)

Did you ever do the op amp upgrade on your own unit? Was it worth the effort?


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## jeffp (Jan 18, 2015)

I have one unit that has the op amp upgrade. The audio board was upgraded and the front panel op amp was upgraded. After the upgrade you are able to turn the volume to maximum without any distortion of the unit output. 
So you could say it is worth it, but the mod costs about 70.00 USD plus the labor to complete the work.
I think it is most beneficial for the 7909 pullout and L models. Those units have the older op amps and the distortion is more apparent then on the 7909J unit. The 7909J unit has better op amps the 4580 in stead of the 15532 op amp.


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