Modification & Upgrade Head Unit Pioneer KEH-P9750

This old car head unit, the Pioneer KEH-P9750 is my car audio head unit for quite some time. This was my dream head unit since I am into this car audio. I am lucky to have one, in this great condition like this.

The reason why this Pioneer KEH-P9750 is amazing, is because it has the advanced audio setting features that other brand doesn't have at all. I was using this head unit as external DSP receiver and you can check the post here. In this post, I will open up this head unit and let's see what I can do to make it better.

The service manual for this Pioneer KEH-P9750 is available online and by that, I can easily spot about what modification I want to do in this head unit.

Fast forward to the head unit, I already dissemble the unit and I am too excited until I realize that no photo taken during that process. Sorry:)

So lets just continue anyway.

The first modification is change the BUS cable to direct AUX input cable. I don't need the whole BUS cable since I am not using CD changer or any accessories using this BUS connector anyway.

By connect directly the cable signal to the R121 and R122 near the IC702, I am now have the AUX cable taken directly to the main board of the unit. This makes the unit look cleaner and less cable going around at the back of the unit.

You can spot on the bottom of the PCB, I also change the capacitor with Sanyo Oscon. It is easy to spot because of the purple color capacitor that work best for digital power supply.

The next upgrade is changing the capacitor. This head unit capacitor are mostly using standard grade Elna capacitor. They are actually good capacitor but in standard, non audio grade capacitor. That is why I will change the capacitor with Elna Silmic for better sound quality.

The input capacitor after the AUX input cables are the first capacitor I change with Elna Silmic. This will be a huge improvement over the stock capacitor that Pioneer use on it.

Next capacitor upgrade is label C111 and C112. They are signal capacitors between audio selector IC to DSP section. The components arrangement between one section to another is quite unorganized, this can be effect to the signal noise from the other components, especially when the signal pass through the power supply section.

This is the view of the bottom of the PCB. The components should be gently remove to avoid the PCB traces break.

The other signal capacitor need to be change is this 6 capacitor behind the RCA output socket. You can change all of them, but you can also choose what capacitor you want to change and let the rest stay as is. Like myself, since I am only using the FRONT output, then I only change only two capacitors that connect to this output only.

I changed the power supply capacitor, but the value is reduce from single 4700uF/16v to dual 1800uF/16v. The capacitors is the high grade Panasonic FC.

It is all done and now is the time to put all head unit parts back together.

I placed the additional switch in series to the front tray motor. This old type head unit doesn't have the option for disable this auto open for the front panel. It is always open and close while you turn the ignition key OFF. So this switch is really helpful to for disable this function. You still need it to return back to automatically open close front panel for the auto sound adjustment procedure.

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All components are in it's placed including the cassette mechanism. This modification didn't give any obstacle to the cassette mechanism to fit into it.

Once it is all finished, then the head unit is ready to put back in to the car.

The audio source for my car is using iPod video 5th gen. This directly connect to the cable AUX I have installed directly before.

The sound after this modification is a lot improved. The background noise is quieter. The vocal is more presence, the detail is good and the treble is smooth.

So this is all modification I did to improve the sound quality of this old head unit.

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