drurywoodson

I had my factory head unit out of the car and opened up today. After taking a bunch of pictures I put it back together and hooked an oscilloscope up to it while it was in the car playing a test CD I made of a maximum amplitude sine wave.

Anyway, if you are thinking of doing any aftermarket stereo upgrades, you'll probably want to know the following:

The HU is made by Pioneer and the model # is FX-MG8227ZT. The service manual is available for $28.39 from Pioneer parts at (800) 421-1404 (6:00AM-4:30PM PST M-F).

The audio signals going back to the amp measured 5.7V peak-peak . The amp seems to have roughly a 15Kohm input impedance and the HU has roughly a 600 ohm output impedance. To get access to that signal you'll either have to hack into the wiring harness or open up your radio and attach some leads to the main circuit board.

What's interesting is that volume control, balance adjustment, fading, and treble/mid/bass control are all done in the amp. The rotary encoders are sending their signals over the AVC-lan to make the adjustments. If you don't have the factory amp hooked up, you can't control volume, etc. with the *****.

So, if you plan on going aftermarket amps, you will either need to do LLC's from the amp's speaker outputs, or else you'll have to add some kind of processor such as Alpine's PXA-H700 that will allow you to make the volume/bal/fade adjustments with it's controller.

The HU is actually very easy to remove from the car, and it's also easy to disassemble & reassemble. The only trick is that two of the four bolts for attaching it back to the car are very deeply recessed, and if you drop a bolt during removal or reinstallation, it will fall to the bottom of the central dash console, where you may or may not be able to retrieve it. If anybody ever figures out a method for doing that operation safely, I'd love to hear it. I managed to lose the bolts 4 times today, and only recovered them twice. So... I've got some more work to do tomorrow.

I did all of this with the non-Mark Levinson system, but I'm sure it applies equally to the ML system. I believe both systems use the same HU.

--drury

drurywoodson

I received the schematics for the HU yesterday from Pioneer. The schematics cover both the FX-MG8227ZT & FX-MG8327ZT. The FX-MG8327ZT is the Mark Levinson unit, and there are no electrical differences that I can discern. They both use the same controller chip with the same ROM code, so I still think they are interchangeable. The only difference I can see is the Mark Levinson logo on the faceplate of the ML unit. However, the manual does point out that the connectors to the wire harness are different for the ML amp and the Pioneer amp, so you couldn't freely interchange amps without modifying the wire harness.

dizzle

thanks for all the good info.

RMMGS4

iTrader: (5)

The IS300 factory radio appears to have a similar configuration where the volume, balance, etc. are done within the amp. I'm not sure if it is sending signals over an AVC-lan as in the the RX though. On the IS amp, you can tap into the low level outputs and avoid using LLC's altogether which allows you to control your aftermarket amps through the factory head unit.

Take a look inside the RX amp. Again, I'm not sure if it is the same amp as used in the IS, but if it is, then look on the daughter card for silkscreen identifying RF, LF, LR, RR mute, & GND. This is where I tapped into the low level outs.

Lexterious

Sorry to resurrect an old thread, but if possible could you describe how you removed the head unit?

I'm thinking of adding a Pioneer AVIC-N1 DVD/NAV unit into my RX330 and am looking for ideas on how to do it.

I thought it might be useful to do some exploratory surgery to see what I'm going have to deal with in the stock unit; how much space I have etc.

Also, if someone has any idea how to get the replacement faceplate described in this thread:

https://www.clublexus.com/forums/sho...ight=faceplate

please let me know.