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Joined: May 02 2017
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Back when I bought my car, the navigation that was in was caput and I messed about with the screen for a while to see if I could make use of it as just a screen. That was to no avail so I was looking for something to fill the hole. Toyed with the idea of one of these android gps thingys and then stumbled upon a post that Marty had made on another forum a while back. That sealed the deal and this just arrived this morning.

I just thought i'd ask what the best way of getting it into the dsp amp setup is. The last car I had, I wired a 3.5mm jack to the cd changer outs on the back of the radio. Suited the purpose and I could plug a phone or a tablet in. You needed to have a cd in the changer though to fool the car into thinking that it's playing. This is slightly different as it has it's own amp. 4x45w @ 4ohm. What's the way to go about linking it in?

Original radio is still in place and I wasn't going to remove it. Just a left and right from the new one into the old system will suffice. Unless someone has a good idea.

Thanking you much so!

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I'm very much convinced that Marty's knowledge 'over there' is just as valid over here...
Just be nice to him and he will come up with some solutions

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Of all the different systems fitted to the P38, the DSP one is the worst when it comes to wanting to fit anything aftermarket. As most of the processing was done in the DSP amp, there's only a stereo output to the amp and a separate output for the sub. You'd need to bypass the amp so the left and right feeds to it are linked to the front speakers and run a separate two pairs for the rears. Ideally you'd need to add some crossovers too. Having looked at the work Marty has done and the grief it has caused him, I'm really glad I don't have a car new enough for it to be fitted with the DSP system.

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Joined: May 02 2017
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Just got home and had a read of the wiring diagrams. There appears to be lineouts (audio out L and Audio out R) that may be suitable for wiring into the cd changer as I previously did with the 3.5mm jack on the old car.

enter image description here

So that would make it Audio out L goes to the Green wire of the blue connector on the radio and the Audio out R goes to the Purple wire of the blue connector. And ground to ground obviously. No need to use the sub output as the dsp will sort that out.

Am I right or wrong?

I know it's Heath Robinson but there isn't much choice.

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Joined: Dec 30 2015
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Gilbertd wrote:

Of all the different systems fitted to the P38, the DSP one is the worst when it comes to wanting to fit anything aftermarket. As most of the processing was done in the DSP amp, there's only a stereo output to the amp and a separate output for the sub. You'd need to bypass the amp so the left and right feeds to it are linked to the front speakers and run a separate two pairs for the rears. Ideally you'd need to add some crossovers too. Having looked at the work Marty has done and the grief it has caused him, I'm really glad I don't have a car new enough for it to be fitted with the DSP system.

And the biggest thing was that I didn't have the DSP system... when I bought mine, the DSP amp was missing, so it was a case of make something work. I could have gotten away without the crossovers et-al and just fed full range to everything, and it would have worked - but I like my audio to sound somewhat decent, hence making the crossovers.

If I knew then, what I know now about the head unit being the same as for the later non-DSP stereo setup, I would probably have bunged an amp board in mine a long time ago and been done with it!

But even so, the DSP system, unless it's running how the factory intended and the amp hasn't shat itself, then it's just a PITA to do much with.
However.....

blueplasticsoulman wrote:

Just got home and had a read of the wiring diagrams. There appears to be lineouts (audio out L and Audio out R) that may be suitable for wiring into the cd changer as I previously did with the 3.5mm jack on the old car.

enter image description here

So that would make it Audio out L goes to the Green wire of the blue connector on the radio and the Audio out R goes to the Purple wire of the blue connector. And ground to ground obviously. No need to use the sub output as the dsp will sort that out.

Am I right or wrong?

I know it's Heath Robinson but there isn't much choice.

In your case, I would either try the line outputs (they probably won't be much good as they possibly won't be what the level is that the DSP amp is expecting), or make 2x attenuator units up, and use the LHF and RHF output from the android unit, through the attenuators, to the front left/right feeds to the DSP amp.

As your factory head unit works, etc, keep that so it's powered, and then it can do the controlling of the DSP amp, for final volume control, fade/balance etc.

You may need to wire the sub into the output from the android unit, as I'm not 100% convinced the subwoofer is fed internally from the DSP amp - if it was, why would they run the wires from the head unit for it? especially when they didn't run rear/left right from the head unit... so if the sub wires aren't used, then why are they there etc...

If you are using the audio out L/R (D2/D3 on your sheet above) then these will be line level. If you use the wires in the main connector, then these will be amplified. You'd also be better using the FL +/- and FR +/- (white + white/black and grey + grey/black) through an attenuator circuit to the vehicle wiring.

If you wanted to do it 'properly' then I'd rip the DSP amp out, and replace it with something like my DSP replacement board, which has 4x door amps on it - and then wire in all 4 corners from the android unit (thru attenuators) to the appropriate doors. Then the nav unit is controlling all the audio, and you could probably sell the working DSP amp for a bit and cover the cost of the install...

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Thanks for the input Marty. I'll have a look at it tomorrow.

I agree that the proper way to do it would be to rip it all out. It would be pretty straight forward then. At this moment in time though, i'd prefer to do a minor mod and retain the original gear.

I think the sub is internally fed from the amp. As I say, on my first car, I wired a 3.5mm jack into the cd changer outs on the head unit and it worked a treat. As far as the amp was concerned, it was just getting left and right audio from the cd changer so distributed the signal accordingly as it usually would have.

Looked at buying a couple of attenuators. What would I need to make my own? My nearest bits and bobs shop for that is Maplins.

Did you manage to get the steering controls to work? I see from your wiring write-up that it's a single grey/orange wire. Do the steering controls work on resistance? I have 2 wires on the new loom. One says Key 1 and the other says Key 2. will one of these connect to the steering control wire and the other go to ground? Or will it not work at all? Not bothered, but if I can get it to work that'd be a nice touch.

Had the unit powered up earlier for a look around and it seems good. Decent speed navigating menus, Bluetooth and internet linked up fine and GPS worked on both built in maps and google maps. For 80 odd quid, it looks like it'll be fully loaded all in one box solution. Need to get the dremel out though.

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I still believe the amp get it's sub feed from the head unit. Plugging an aux into the CD changer port won't have any effect on what the head unit outputs.. just because you put a L/R feed in and the head unit outputs L/R doesn't mean it doesn't output the sub aswell - it just means that the bass frequencies are filtered out of the incoming feed, and send out a different output.

I know there is a guy on the other forum who believes that the sub is all done in the amp - and I haven't looked at the sub input/output on a DSP amp to confirm or deny it... but in my head, the head unit must do something with a sub signal, as otherwise why are the orange/orange black output wires there... if they weren't doing anything (like the rear left/right don't) then why weren't they removed (like the rear left/right were from the loom on the later ones).

Attentuators are easy to make - have a look on Rangerovers.net, or google P38 attenuators. It shows the layout of them and the components needs. Ray A designed them years ago now to convert the output level from an amplified source to the level that the P38 amps are expecting to see (which is also higher than a standard line level signal).

Steering wheel controls are easy.. Connect Key 1 to the grey/orange wire in the P38 loom. Done. The head unit has a 5V reference feed on that wire, and then measures the voltage drop when one of the steering wheel buttons are pressed. The software on the unit records an action against the voltage it measures when each button is pressed. So simple and easy.

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Diagram for the attenuators http://www.rangerovers.net/rrupgrades/entertainment/headunitadapt.html

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Thanks very much. I'll make a start on all that now. Got the Dremel.

Regarding the sub output, I suppose the easiest way to find out would be to disconnect the sub feed from the head unit and see what happens. I see what you're saying about the wire being there but it seems strange that the feed goes to the dsp amp first, and then onto the sub. In PA systems, you'd have a left and right going out to the crossover and then on to the amp. Could the sub out on the head be full range that gets filtered later, or could there be a low pass filter within the head??

Thinking about the 3.5mm jack I wired in to the cd changer L&R on my first car, it seems funny that the signal is run from the changer to the head and then back down to the DSP. Why not just run it direct from the changer to the DSP? What role does the head play in the signal path?

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Disconnecting the sub feed would the the easiest way to tell, yes.

My best guess, is that the output possibly has a low pass filter on it in the head unit, which is then fed to the amplifier. Since the subwoofer has it's own amplifier in it, again, my best guess is that the DSP amp does the audio control of the subwoofer signal, in relation to what the head unit is telling it to do when the subwoofer control is changed.

OR it might be the output from the head unit IS full range, and the DSP amplifier then has the low pass filter in it, and then manipulates the level to send back out to the sub amp.

OR it could be that the 2 wires do nothing, and the subwoofer derived the bass signal from the left/right that it is fed, and then manipulates the volume and sends that to the sub amp - as suggested on the other forum.

I've never actually had the (dis?)pleasure of having a working DSP amp in front of me to test and see how the various signals are mixed/filtered etc. As I mentioned above, the DSP amp was completely missing in my RR when I bought it, so pretty much all of my research has been around the nicest ways to adapt the system to work with another head unit, or amps etc, and avoid the cost of a replacement DSP amp when I first bought the vehicle... That and it's infinitely easier to work with aftermarket gear without the DSP amp!

The head unit in the CD changer/aux in scenario is acting as the switch for what the amplifier is getting it's signal from. Yes, you could probably wire a line level signal direct into the amp feed, but you'd have very little control over it if the head unit was disonnected. Going through the head unit, you can then control all the parameters of the audio, and obviously switch between the external source and the radio etc.

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Don't worry, if my DSP amp is still working next time I'm down (and I'm sure I will be sometime!) then you can have at it. I think it sounds good when fully working but I won't be spending hundreds to replace it once it goes. Things have moved on a bit since 2001.

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I already have a funny feeling that if your DSP amp stops working, then you'll be coming down anyway... probably for me to put something more reliable in it's place...

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So far so good. Pretty pleased with the fit. It's a snug push fit from the back. I'll secure it tomorrow with some sort of glue.

enter image description here

enter image description here

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That is pretty slick, and I do like your LPG switch too.

Marty, you know you're right :)

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Just about done. Cocked up the bottom right corner a bit, but a bead of unibond waterbased black silicone (doesn't go shiny) all the way round should sort it out and finish it off nicely.

2 hitches.

Radio stations aren't saving. I thought I'd wired it up right. There are 2 wires for 12v. A thin red one marked "ACC" and a thicker yellow one marked "12v". I put the yellow 12v to the purple 12v constant from Marty's writeup and the red "acc" one to "white/pink". The thickness of the wires matched up but perhaps these 2 need switching around?

Also, I wired the grey/orange steering controls wire up to key 1 as marty suggested, but nowt happens. Should I try key 2?

Other than that, works like a boss. I took out the interior light fitting and put the gps receiver up inside the roof. Ran the cable along the roof, down the windscreen trim into the dash.

enter image description here

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sorted the steering controls. looked around the android system and found you needed to choose the function, then set it by pressing the button when asked. Just need flip the 12v wires andall done.

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Looks good,

Yes - as you've found, the steering wheel controls need programming - which is good as you can map them to whatever you like - eg on mine I've swapped the seek and volume ones over (the diagrams on the wheel have worn off already) as I'm left handed and always went to control the volume with my left.

12V live is usually red, and switched is yellow, so swapping those around should sort the rest of it out.

How did the attenuators go with the audio level to the DSP amp?

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Joined: May 02 2017
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Everything's good. Great signal levels. My sub is still out of action until I respeaker it but funnily enough, the eq available on the new unit allows far more dynamic range than the original head. Cycling through the presets, I was surprised at how much more you could get out of the system instead of just the basic bass and treble. Sounds great even without the sub. Speaking of which, do you have recommendations of some cheap/cheerful replacements?

After i'd posted about the steering controls, I remembered i'd read or watched a video about setting the keymaps. That's when I went looking. There's an endless amount of options but only 5 buttons. lol.

Stock sat nav works good although I downloaded google maps as I like that. GPS picks up straight away with good signal strengths.

Called the Mrs through the Bluetooth connection and she said the sound was good (she's usually dead critical) so the microphone must be half decent too.

Changed the boot logo to Land Rover and downloaded a few things from the Play Store. Torque works good so have basic on board diagnostics too.

All in all, I'm well pleased and apart from my little cockup with the file at the lower right hand corner, I think it almost looks factory installed. I'd recommend the unit to anyone wanting to do the same thing.

Getting married tomorrow so unless I have time in the morning, the 12v wire switcheroo will have to wait.

Thanks for the help. :-)

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Glad its all working well for you. Which one did you buy? Contemplating fitting one to my HSE (no DSP to worry about!) but retired defeated from the sheer apparent choice out there.

Clive

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This is the exact one that I bought. The others were slightly smaller overall and some had a lower resolution screen.