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DSP Amp Replacement Project

15K views 20 replies 8 participants last post by  lwt  
#1 ·
Figured I'd start a new thread as a spin-off from the other recent DSP amp thread where I'd mentioned about the idea of fitting a plate in the back with normal door amps and then using them to drive the speakers in the later P38's with the dreaded DSP amp failure problem.

I had previously done a 'proof of concept' on the workbench:


Which was just a crude wiring loom I soldered up and then plugged in to some bass speakers, and a single mid range that I had lying around.

I've now got some 1.2mm thick aluminium sheet (want to keep the weight down where possible! especially if I end up making them into kits that ship out!) so marked it out a bit bigger than the DSP amp so everything will fit nicely. I've hopefully even got some spare space to work on a telemute option for the Navigation equipped vehicles.

After marking and drilling out the holes that matches up to the DSP amp mounting holes, I spaced, marked, and drilled holes for the new amps to fit on the sheet.

After drilling, the 4x amps were fitted with self-tapping screws and then I trimmed the threads on the back so they didn't stick out as far.



After that I used the old connectors from the wiring loom that I had made for the bench test, and started crimping up some new wires for it.
Only got as far as power, ground, and remote wake up done this evening - I wanted to start with them as they are the common ones across the 4 amps.



Tomorrow if I get some time I am going to come back past the workshop from a house call to a BECM lockout, and take the amp board with me and do a 'test fit' to the Vogue that I have and will be the recipient of this first kit. Mostly to make sure there is enough space in there for everything and it's not going to get in the way of the trim and all that. The I'm going to work on all the signal wires in and the speaker wires out. Everything will be labelled so as far as installing the kit goes you should be able to bolt the amp board in place, and then cut the DSP amp connector off and solder/heatshrink a bunch of wires together, run the extra 4 wires for the rear left/right signal, and get some sounds...

I'll update as I get a bit more done..

Marty
 
#4 ·
They were the ones I had kicking about so figured that I'd use them to start with!

The later system with door amps has different part numbers (AMR6355 and 6356) but there is obviously still a different part number for the rear amps - so I am guessing the difference must be something to do with the extra tweeter on the front doors, possibly slightly different impedance with the extra speaker in line.

I might take the cover off one of each and have a look to compare the internals at some point.

They still seemed to work OK with the alpine head unit when I had it set up as the test system on the bench, so confident that it will be all OK when it's fitted to the vehicle.

I am thinking about making a little top 'water cover' to try and prevent water dripping in from the top, which going by the DSP amp that came out of the vehicle, is probably what killed it. If the corrosion in the connector is anything to go by anyway!
 
#6 ·
I will be trying to do a bit more over the next couple of days... currently have a window switchpack to finish repairing, a door latch to build, and a BECM to unlock for other people...

Then I've got to check the seal at the top of the windscreen, the front sunroof drains, and replace the O2 sensors on my own P38 before I have a clear list (and work bench!) to continue on this project...

I also had a bag of HEVAC LCD screen repair connectors turn up from China today, so I have to make sure that they are made to spec and work aswell!! So much for some of this 'time off' I was hoping to get this month :)

Will keep you all updated though...

Marty
 
#7 ·
Well, I finally got through my pile of door locks, BECM's, window switchpacks etc that were scheduled in this week to be worked on for other owner, so had a bit of a tidy up and some 'me' time with my own projects... namely this one!

I did a test fit last weekend up at the workshop in the '00 that this will be going it (I tested the DSP amp, and it's a no-go - I think as I posted above!) and figured that the mounting way needs the wiring reversed to come out and meet up with the vehicle wiring properly.

Luckily I was just able to reverse the connectors, and now the wiring comes out the other way.

Got all the input wiring done today, including the extra loom for the rear left/right input cables - which now have ISO terminals crimped on - so that loom can be run up the LH sill to behind the radio.

Just have the 16 output wires to do now, and then it will be ready for testing! Going to have a hunt for some wire to match the vehicle colours, but I have a feeling that I won't be able to match them all... However, my plan is that I'll just label everything with what colour it should connect to in the vehicle and then any mismatches in colour won't be such a big deal...

Watch this space... I may get it done before I bugger off for work for a couple of months!



Marty
 
#8 ·
Update

Well, I've been away a bit over Easter, but I managed to order some more cable before I went away and it turned up whilst I was gone, so that was the final piece in the puzzle on building this.

I managed to find a place that does wire for automotive looms in loads of colours, including all the ones I needed for the speaker outputs to match the vehicle wiring loom.
The colours for the rear inputs on this one are different to what the mid/high line vehicles, as the place I originally got my wiring from didn't have the same colour combinations (but going to check with the new supplier so they can all be correct)

So - have got all the output wires crimped and loomed up, nearly ready to install to my spare P38. I just need to get the tips of the wire ready for soldering to the vehicle loom.

Wiring all completed and labelled.


Close-up of the connectors:


Output wires for the speakers:


Wiring loom with 5m of wire to get from the loadspace to the head unit. These are crimped with ISO terminals so they can just be inserted into the existing connector to make it as 'factory' as possible.


Next stage will be to install it in the X-reg I've got, with the dead DSP amp to make sure it works properly, and there's enough wire on the extra signal wires etc.

The only issue is that I'm going to be heading away in a weeks' time for nearly 3 months for work, so may or may not be able to get it tested before then - and even if I do, and it works all as intended - then I'm not going to get a chance to work on any more of these before I'm away, so it is going to be a summer job to get a few of these made, priced up and ready for anyone who is wanting a cheaper alternative to trying to find a horrifically expensive replacement DSP amp..

Marty
 
#9 ·
Re: Update

Looks good Marty! We're all cheering for you putting in so much work for a 15 year old car.

One point I can make for the sellability (its a word) of these units is to ensure that it can be simply plugged in to the DSP connector.
So if that means the weird locking plug can be on the end of the wires that would be fantastic.

I have no issues with cutting in to my electrical and soldering/crimping in new ends, but it would be so much better if I could simply plug it in and change between that and the Disco 2 amp I currently have in.

Cheers,
Garrett
 
#10 ·
Re: Update

Hi Garrett,

Thanks for the comments!

The only problem, connector-wise is that you can't get the DSP amp connectors - they are some special kind of connector that I can't seem to find anywhere (think they are obsolete). My only other option would be to try and round up a load of dead DSP amps, and try to re-use the connectors from these - though they are all PCB mounted, not inline - so think you'd then end up with a proper mess of wiring somewhere. So unfortunately I think the simplest, and most cost-effective solution (and probably only solution given the connectors seem to be unavailable) is to cut the vehicle connector out and solder the wiring together. I'm planning on supplying the kit with all the wire ends pre-tinned for soldering and with heatshrink on them.

I did consider putting a connector on the end of the wiring loom, but either way you still have to reconnect something, so solder/heatshrink is probably going to give a better connection in the long run.

I'll keep looking to see if I can find the connectors anywhere, but current searches have been pretty futile :(

Cheers,
Marty
 
#13 ·
Re: Update

Right, well, it's been awhile since I've updated this - mostly as I've been away working until the end of Jun, and then playing catch up on window switchpacks, door latches and the likes since then.

Well, today I managed to get up to the workshop and actually wire this into my 2000MY vogue which is in for restoration, but more importantly for this project has a faulty DSP amp...

So got into the back of it today, stripped out the trim, and then got comfy with the soldering iron and heatshrink:

Pulled the wiring loom out and remove some of the tape:


Wires cut to length:


Starting on the solder connections:


Subwoofer wires just join together to get the signal to the subwoofer amplifier


Finished the connections to the amp board:


Running the extra wiring to the dash for the rear left/right feeds


Through the sills with the vehicle wiring looms:


Along up to the passenger footwell, and then around under the carpet:


Wiring run into the dash:


Extra wiring connected to the ISO block


Head Unit Connected:


All wired in:


Couple of video links to the system actually working when it's wired in. The front/right doesn't work as the amplifier is dodgy, so I need to take a spare up with me next time. There are a couple of speakers that don't work aswell, but I'll get around to swapping them out when I'm pulling the doors apart to clean them all up.



I'd forgotten how good it sounds with the factory amplifiers.. I think I'm going to have to make up a board for mine, fit it, and put attenuator circuits on the output of my new android unit...
 
#15 ·
This is in one of my restoration project P38s... it came with a DSP amp, but true to form it is faulty and doesn't actually work...

It is also missing the subwoofer and CDL changer unit, but as it's currently driven from the factory head unit, yes, they will plug straight in and work, as this doesn't do anything to that wiring, other than link the sub feed at the DSP amp connector.

On my own P38, stereo world's I fine - it uses the amp in my new nav unit to drive the door speakers, bur after hearing the factory amps, I might look at fitting one of these to mine too!
 
#17 ·
Sub unit would be great at some point - I think I have a couple of Alpine CD changers kicking about too - though I'm looking at replacing the factory head unit/navigation with an all-in-one unit like I have fitted to mine - but that's a bit further down the road - got a lot of work to do to it before I'm ready to start installing new stuff!!

I've still got your spanners here (they are in the garage at home now) so they are safe for whenever it works out that we can meet up to get them back to you!
 
#19 ·
Another Update...

Just as an update to anyone still following this...

I have had a bit of spare time now I am away for work, and things have settled in a bit more. So I've been spending some time doing some research and am fairly confident that I have found the correct connectors for the door amps, direct from a supplier in China.

I've put in an order for 50 of them, which is a lot better than the last supplier I found that wanted a minimum order of 250. So hopefully in a month or so with the slow shipping times for things coming from China, I should have the first load of connectors. Assuming they are the correct ones, then I will order a second batch, and then hopefully be able to start making up some DSP replacement kits, and also supply just the connectors and pins for those who want to make their own units/wiring looms.

Next on the list... it's back to making a system that will mute the audio and then play navigation instructions through at least the drivers door, but preferrably through both front doors.
 
#20 ·
Re: Another Update...

You can borrow my other half, she's like a sat nav, she warns me about every speed camera and never shuts up, doesn't need wiring up,, more tying up and gagging, lol,, on a serious note, when your back , will pop up with the sub I have for you, have a look at yours why I'm there, could do with an upgrade, my dsp will get snatched up quickly for sure,,
 
#21 ·
Re: Another Update...

I have now replaced the DSP with 4 door amps, as per Martys design and am very please with the result. Thanks to Marty for the DSP wiring guide and for providing the connector shells and crimp pins to fit the door amps. I did it all pretty much as on page 1 of this thread but I used crimp connectors rather than solder.

I initially considered building something that would sit in the old DSP frame and use the DSP connector, but on disassembling the DSP I soon gave this up. The connector is a push fit directly into a PCB where a lot of commoning is done. Even with this PCB removed it looked like much more work to solder to each pin than just to go into the wiring loom.

Using the wiring guide I ordered lengths of cable 32/0.20mm in all the required colours from Vehicle Wiring Products, and also the matching in-line crimps and some heat shrink sleeving. I also bought an ISO connector and pins to add the rear speaker outputs from the head unit. Although I only wanted the pins it was easier to buy a whole shell + pins. This turned out to be a good thing later on.

Using the same wiring colours as Land Rover made it very easy, and i would recommend this as well worth the effort. I first made up the 4 door amp connectors with flying leads, about 0.7m long. Then using the wiring guide I snipped pairs of wires from the DSP connector, slipped short lengths of heat shrink over them and crimped them to my flying leads. For the wires that need to go to each amp (power, earth and the switched wake-up) I considered crimping into a large bullet but eventually went for Helacon Push In blocks (also from Vehicle Wiring Products). These worked out fine. The DSP input and output wired for the Sub Woofer were just joined direct, no intermediate amp required. The amps I mounted onto plate that fitted the old DSP mounts. There is enough room for this to be quite a bit bigger than the old DSP giving plenty of room to fit the 4 amps. I used nuts with locking inserts throughout.

To add the L & R rear speakers I laid cables inside the car alongside existing looms by removing the kick plate trim panels and the small panel at the base of the front left A pillar. It was then easy to pass them behind the glove box and out into the head unit. I also included two extra wires for the nav audio. My original plan to add the 4 crimped connectors to the existing brown ISO connector on the head unit failed when the new crimps proved slightly too large to insert into the ISO. Instead I extracted the standard crimps and then put the whole lot into a new ISO connector. A small 8 Ohm speaker from a dead computer was added for the Nav voice and tucked behind the dash trim.

Power on and everything worked fine, the standard sound which I find quite rich and pleasant was back with lots of volume and of course all the F-R and L-R balance works. The Sub woofer is fine and I have the Nav voice if I want it. I thought of ways to add this to the front right speaker but I always find nav mute a nuisance as it always seems to mute at either a good bit of music, a vital bit of narration or when there is a traffic announcement for the road you are on! So i'll leave it for now.

I hope this helps someone else and encourages others to have a go, especially if you want to leave the interior looking standard.