External DSP Using Pioneer KEH-P9750

The Pioneer KEH-P9750 is a hi-end car cassette player built around 90's. The audio features in this head unit is beyond of it's era. It has built-in sound processor, 6 channel time alignment, 13 band equalizer and auto EQ by using the mic for the sound adjustment. It also included internal power amplifier rated 4 x 45 watt which enough for simple car audio setup.

I will not using the cassette player on this Pioneer KEH-P9750. It is outdated for today media standard. I also never play music from the cassette anymore.

This head unit is great. I don't want to waste this head unit consider so many advance audio features on it. That is why I will using this Pioneer KEH-P9750 on my car as an external DSP to adjust and tailored the overall sound.

Before I begin this head unit installation as an external DSP, this are the things that need to be consider.

1. I bought this Pioneer KEH-P9750 in this great condition for less than $30.

2. You cannot setting the DSP features without the remote control.

3. The front panel head unit display using the back-light that mostly problem due to ages.

4. I also replace the ribbon cable that attach the detachable front panel to the main unit. The total repair cost for the back-light and the ribbon cable are about US$50 at the authorized Pioneer service center.

5. You will need a pair of RCA female cable to connect from the OEM head unit line out to this Pioneer KEH-P9750.

The first step is finding the IP-BUS connector pin at the back of the Pioneer KEH-P9750. The detail information about all of this IP-BUS pins function is describe like in the picture bellow. This picture is taken from the Pinterest and the credit to the owner.

There are 4 pin need to connect as the line input.

R+ input = Right channel positive input
R- input = Right channel negative input
L+ input = = Left channel positive input
L- input = Left channel negative input

The negative for the Right and Left channel can be combine as common ground to the source unit.

On the photo bellow, I directly solder the line input cable to the internal PCB. You can do with the same result by just using a tiny pin to connect to each pin on the IP-BUS socket.

Now this Pioneer is ready to install as the external DSP.

The working principal is the line input that taken from the IP-BUS above will be feed from the line out of the OEM head unit. Then the speakers out from the OEM speakers are now connecting to this Pioneer KEH-P9750 speakers out.

We want to turn ON this Pioneer KEH-P9750 as an external DSP once the OEM head unit is turning ON. So the ACC cable from the Pioneer KEH-P9750 (the cable color is RED) is connected to the REMOTE TURN-ON (mostly the cable color is BLUE with WHITE strip) from the OEM head unit.

The Pioneer KEH-P9750 power cable (YELLOW for positive and BLACK for ground) should also connect directly to the positive polarity of the battery and car body as ground respectively.

The Pioneer KEH-P9750 need to power ON once, then it will be turn ON or OFF depends on the ACC cable that previously connect to the OEM REMOTE TURN ON cable.

Finished with those connection, then it is time to setting up the OEM head unit first. The audio setting on the OEM head unit should set to all flat. All Bass and Treble position are in the center. Loudness turn OFF. Speakers FADER setting are set to center. The volume control are way down to zero.

Now we go to the Pioneer KEH-P9750 DSP setting.

Go to the menu function and enable the AUX input.

Turn ON the unit, it will goes first to Radio. In this step you will hear the sound of the radio static noise through all speakers.

Then select the source to the AUX input and the the volume control in the Pioneer KEH-P9750 rise about 50% to the maximum.

Then use the Pioneer mic to setting the EQ and time alignment automatically. This steps are explain on the Pioneer KEH-P9750 user manual.

Finished with this setups, then start to rise the Pioneer KEH-P9750 volume control up to 80% to the maximum then slowly rise the volume from the OEM head unit. You will hear the music that play from the OEM head unit now.

There will be an additional adjustment to setup the gain between volume from the OEM head unit and the Pioneer KEH-P9750 to get the proper gain level.

It is necessarry to adjust the audio setting in the OEM head unit or in the Pioneer KEH-P9750. But I prefer do this on the Pioneer and let the OEM head unit setting keep flat.

At this point you already using this Pioneer KEH-P9750 as an external DSP for the OEM car head unit. This Pioneer as DSP can be stored away somewhere in the car since we don't need to do any seeting with it anymore.

You probably confused why I am not showing the photos like I shared on the steps above. Well, I did this method on my friend car and you can find it here.

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.