Car Head Unit Pioneer DEH-P8850MP Op-amp Upgrade

This Pioneer DEH-P8850MP is one of my favorite head unit. I am quite remember when the first time I saw it on the advertisement, around 2007, I immediately fall in love with the design, especially for the display that came with attractive color. I think this is also the first time for the car audio head unit to put the color display like this.

The most important things is the sound setting in this Pioneer DEH-P8850MP. It have so many advanced audio features package in Digital Signal Processor, which is the specific sound tuning to tailored based on the acoustic room. This sound tuning is made with the combination of auto time alignment, auto EQ, BBE, and multi audio line out.

If you following from my previous post about changing the internal capacitor in this Pioneer DEH-P8850MP with the Nichicon Super Through few month ago, I actually did this upgrade before that post. It is just like back and forth posting, but anyway, let me explain how I did this upgrade.

As usual, the first things to do is open and remove the detachable front display unit. Stored it safely to avoid any scratch and then I start to opening the top cover of this unit. This is quite easy to do since no bolt attached on it, just firmly pull it up.

On the next step, I need to remove the CD mechanism unit. To remove it, I need to find four bolts on each corner of the CD mechanism, then unscrew it.

Make sure the ribbon cable under the CD mechanism is unplug from the main board before take out the CD mechanism completely. This ribbon cable is fragile and easy to break.

At this point, the main board of this unit is exposed and I just need to find the specific components to upgrade.

I found the first component upgrade will the the op-amp near the AUX input socket. It is marked IC441, the dual op-amp JRC 4558D. I am pretty sure this op-amp is for the buffer and isolator for the AUX input. This JRC 4558D is universal op-amp that widely use for any kind application. But for sound quality improvement, this op-amp need to be replace with the better one.

To access the main board completely, I should continue to disassemble the front panel mechanism by unscrew the four bolts on the bottom of the chassis.

I also need to remove the heat-sink at the back of the unit.

The step to remove the main board completely not yet done, there are several bolts on the main board need to unscrew along with the metal tabs that locking it into the chassis. By removing all of them, the main board can be easily lift up from the chassis.

I am inspecting closely the components on the main board and I find Burr-Brown PCM1606 for CD DAC and the AKM AK7732VT for the audio DSP. They are high quality audio processing from the reputable company.

At the bottom of the main board, there so many op-amps.

While I check the schematic on the Pioneer DEH-P8850MP service manual, I spot the amplifier IC use in this unit attach directly to the heat sink without any thermal paste on it. This become common for Pioneer head unit not to put any thermal paste to the heat-sink. Since car head unit will always expose to the extreme temperature inside the cabin, missing this thermal paste is not a good idea. I will fix it later after this upgrade complete.

Going back to the main board, after I read the schematic, the first op-amp will be change is the AUX input isolator. This is SOIC op-amp is so small which require high soldering skill, especially for the tight place like this.

I remove it gently to avoid any PCB trace broken.

The op-amps replacement for this upgrade is LT1361. This high performance op-amps really suitable in this kind application to improve the sound quality.

I put the new op-amp in the main board and solder each pin carefully.

You should in good mood when doing this job otherwise bad result may occurs. Another tips to install the small components like this is by using glue to attach between the op-amp to the PCB first, before the soldering process.

Another op-amp need to be upgrade is at the bottom of the main board. I will replace 2 op-amps marked IC281 and IC283. They are for LPF section after the CD player DAC.

Oops, I made some mistake. I broke the pin 7 on IC283. I am in the good mood but problem may still occur when do the job like this.

How I fix this is simple, After the new op-amp installed, I using the small wire to connect between the op-amp pin to the PCB traces. I bend small wire according to the traces.

Attach the wire to the broken traces then this problem is fixed.

I only do upgrade for those 3 op-amps and let the other components stay as original.

Before I assembly the unit back together, it is a good time for me to clean the whole components, including this dirty fan.

I also put the thermal paste on the IC that will attach to the heat-sink.

Thermal paste are also applied to all voltage regulator at the side of the unit.

Finished with this, it is time to put back all parts together.

The assembly process is the reverse order from the first time I open this unit.

I take this opportunity to clean up the CD optic. I am using a cotton bud and applied small amount of alcohol to clean it.

It is all done.

I test this head unit first before install back to my car. I should make sure nothing wrong with it after this upgrade.

This is my listening impression after this op-amps upgrade.

I am using the iPod in this test using the line-out adapter that directly took the line out from the iPod DAC. The music files are mostly in AAC format.

After this op-amps upgrade, the sound transparency and detail is noticeably better. Especially for the mid-range presentation is more presence, more live.

Then I changing to CD as the music source. The sound is now way better than before. The sound-stage is wider and detail is far improve but without any harshness. The vocal presentation are more forward, more lift above the dashboard.

I am pretty sure this op-amps upgrade is not easy to do for most people. But this effort give paid with the better result in the overall sound quality.

Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.