Harman Kardon head unit replacement - notes

Hi,

I've just replaced the head unit in my V8 ES Disco 2 and thought I would share some of the details for those that may be looking to do the same. There's a few guides out there, but nothing that seems to put it all together, so hopefully this isn't all old news!
The following is just some notes for people assuming you already know a bit about wiring up ICE.

The head unit is thankfully a standard single DIN. You can get a piece of plastic for a tenner or so that hides the screws you will expose with a standard single DIN replacement.

I was swapping the stock unit out with an old ( but excellent ) Alpine head unit that I've had for years.
Standard ISO fitments so no problem. I'm not bothered about steering wheel controls so ditched them completely, a task for another day!
I also only used the standard antenna fitment. The mini-fm antenna fitment is meant to give slightly better FM reception, but naff all mw/lw. I can't really notice the difference tbh!

During first test I noticed was that volume control was VERY twitchy. Anything past the first couple of notches was massively loud and distorted. There was also an awful amount of alternator whine when I drove it.
That's when I realised there was going to be a hidden amp somewhere in the car attached directly to the speaker-outs

So, assuming you have the Harman Kardon set up you can identify the amp setup. It's under the passenger seat and you should be able to see it with a torch without removing anything. It will be badged 'land rover' but it's a HK piece of kit. The CD changer under the drivers seat appears to be Alpine.
If you remove the plastic around the bottom of the seat you will see the big audio plug on the front of it with 20 wires or so ( 8*2 plus live/ground ? )

There are two options in the above scenario. One is to pull the plug from the amp and splice the connections for fr/fl/rl/rr directly, bypassing the amp completely. This is a slightly too permanent solution for me right now and when I do that, I want to have a custom plug to do it. No scotchloks or solder, I want it simply and easily reversable.

So instead, and given that I had RCA pre-outs, I grabbed a spare ISO block and wired in some RCA plugs. Plumbing this into the head-unit pre-outs drops the output to line level, meaning no distortion and the volume control now makes sense
I can confirm that this absolutely works ( there are some posts on the internet saying it doesn't !)
I'm basically bypassing the head unit amp ( I actually turn it off to keep heat down ) and am just using it to control the HK amp.
There *is* still a very slight touch of alternator whine, but it is now totally bearable.

Another option would be a hi/low level filter in-line. This would be the only option without any pre-outs.

The sound quality from the HK amp either isn't as good as expected, or the standard HK speakers are ****e. However, the overall quality is far *far* better with my new head unit. Plus, I now have mp3 cd playback and an aux-in that works!

I must say, I'm not overly impressed with the HK kit on the Disco. I know it's standard on a lot of luxury cars, but I got better sound out of the stock speakers plus my head unit on several cars prior to this.

Anyways, hope this helps someone.

PS : One extra thing of note, removing the clock makes pulling down wires for an aux-in MUCH easier. It's a trivial removal with a couple of thin credit cards.

An update on this. A couple of ground loop isolators post RCA-outs completely fixed the alternator whine. Set-up sounds pretty good now!

The two aerial plugs, a standard sized one and a smaller one you will find are two aerial systems on the Disco; the wires etched on the rear quarter windows. The one on the offside is the MW/LW and is fed through its own pre-amp to the HU on the smaller plug.
The VHF aerial is etched onto the nearside window and it too is fed through a pre-amplifier to the head unit on the larger standard plug.
You might be able to find a system to combine the outputs of the two pre-amps into the one aerial input (the larger one).
Each pre-amp is fitted above the respective window and the power is fed to each from the "System Enable" wire; pin 5 on the grey plug C0098 (the bottom one) . The wire colour is Red/Blue.
That "System Enable" also signals the power amplifier under the passenger's seat to power up and in some installations can also power one of those automatic extending telescopic aerials.
In the past, I've used it to power one of those small FM Modulators to inject into the radio my music from my phone.