DSP amp fault or not.

Hi Guys,
My year 2000 P38 vogue Harmon Kardon system is dead. It only ever played through the passenger side speakers but now does not play at all. Lights up and selects everything ok but no sound. I did a search and found the following response to a post.

"The 1999 Alpine/Harmon Kardon system uses a single amplifier mounted in the rear near the subwoofer. To test if it's your head unit or the amp, simply remove the Clarion head unit and plug any other make of radio head unit in that has standard ISO connectors. The rear amp is driven direct from standard speaker outputs (unlike the earlier 96-99 Clarion unit). If you regain your lost sound then the fault is in the headunit, else it's the amp, cables or speakers (doubtful). I believe there are crossover units in the doors, but unless you have a wiring fault, I doubt you'd loose the signal to all 3 speakers in the door."

Can anyone confirm if this is correct or suggest how to prove the faulty part. I love the V8 sound but am now starting to miss radio 2.

Sounds like some good advice to me. The amps are prone to failure. If your lucky as I was you will get one from eBay US for $50 brand new !!! otherwise try the sponsor Emmotts or main dealer £££££££

No, it's rather inaccurate I'm afraid...

You may or may not have a single amp in the back - only the DSP systems have the single amp, the non-DSP systems have the same individual door amps as the previous Clarion setup. There are no separate crossovers - the active crossover-ing is done by the amp(s).

And you cannot run a standard aftermarket HU, either - it needs attenuation and impedance-matching to the amps, otherwise it will damage them and give very badly distorted sound. You COULD do it, on VERY low volume, to test whether or not it's your HU or amp(s) at fault... but only do it briefly.

The fact that one whole side (ie one whole channel from the HU, for DSP, or 2 for non-DSP) have failed, suggests to me it's the HU not the amp(s) at fault. The standard HUs are pretty crap.

Do a search, I put up a whole thread regarding this subject...

Hi guys,

It has the single DSP amp behind the sub woofer in the rear.
The H/U has the grey, brown and 20 pin yellow/green and blue multiplug. I have a cheap H/U with ISO connectors but I cannot adjust the volume till the unit is switched on. Is it likely to blow the DSP amp straight away or is there a better way to isolate the problem.

Clarky I have your excellent guide on replacing the H/U and the wiring is as per your doc except I have a pink/black wire on pin 10 - green connector.

Finally how do I remove the small round connector next to the antenna connection on the H/U. I have pulled, pushed, twisted and turned it without success.

Thanks again, Don.

Don, once you remove the original HU you will have very strange things happen with volume control - that's because with the DSP setup, it is the DSP amp gain that controls the volume and not the HU.

Best way to proceed is to have the volume set to no more than 1/4-ish (dont want to high a gain set in the DSP amp as the signal your new HU will give it is more than it is designed to handle!) - then turn off the ignition, then unplug your HU. The small round connector next to your antenna connection sounds like the 2nd antenna - it should have a co-ax wire that looks identical to the antenna wire... and on UK-spec cars it isnt attached to anything. It should just pull off like the other antenna wire - if it doesn't, prise it off with a screwdriver or some such - it doesnt do anything, so even if it breaks, I wouldn't worry about it.

Plug up your new HU and turn it on - but keep the volume RIGHT down, and only do this briefly as fault diagnosis. If you're getting sound from all speakers, your old HU is at fault. If you still get nothing, it's your DSP amp.

Hi Clarky,

Tried that and still just hisses so looks like it's the DSP amp.
Did you get any further with your thoughts on replacing the DSP with an off the shelf unit?

Was the hissing coming from all the speakers? You mentioned that one side wasn't working at all...

Replacing the DSP amp with aftermarket is far from straightforward, unfortunately. You also need 4 passive crossovers, custom-made for the setup's rolloff points... Best estimates of total cost so far puts it around the £100 mark, including a suitable amp.

For the crossovers (if you know how to build them) you need a 100uF non-polarised capacitor and a 1.0mH inductor - these give rolloff points of 398Hz for high-pass an d 425Hz for low pass - when arranged in a simple 'first-order' type circuit - which is about as close as I could get to the original 500Hz rollof point using commonly-available components.

You'd also have to butcher the wiring at the DSP amp plug, leaving no easy option to go back to the original setup!

Another option would be to replace the speakers with components that come with their own passive crossovers (many do) - but that is an expensive option. Or... To just replace the woofers in the doors with full-range speakers, and disconnect the mid-range and tweeters - but this will obviously reduce sound quality...

I've not been able to 'try and test' any of these methods yet, and dont know of anyone else who has replaced the whole system and documented it... Your best option may be to just look for a second-hand DSP amp, and hope it's fully working!

Hi Clarky,

Sorry for the delayed response. Originally I had all the balance turned to the passenger side as the drivers side speakers only hissed. I think I now get just the hiss from the drivers side with nothing from the passenger side. If I turn up the volume I eventually get a loud pop. I don't have access to the car presently to check any further. I guess I will have to start looking for a DSP amp.

Would there be any chance of testing on the DSP connector for an audio input using a headset or small speaker and wires to try to confirm the DSP is the problem before searching for one?

hi don , may i suggest a foolproof way of getting the answer ,easily ,free , saving you going thru a big list of possibilities ,, this worked for me , firstly see if you can find any mates etc who has identical car ask if you can take his amp out and try on your car if his works then resolved its your amp its fxxked try emmotts but i know from yesterday they had none so try bmw breakers cos certain bmws have same amp .or try american e-bay and look for lear amp thats the one you want and make sure u verify the connectors , as i said it worked for me cos i found someone who was happy for me to strip his out and test it on mine and refit back to his all perfect and working ,,,,oh the other choice is you could drive off with his happily listening to your brilliant sound system but then alas youve lost a friend and lastly buy from main stealer in excess of £365 ,00,,hope this helps mozz

Hi Mozz,

Don't know anyone with the same amp and I would be a bit nervous in case I have a fault that could blow the replacement amp. Going to do a search for a replacement, I may get lucky. Would be nice to be sure if it's the DSP first though.

Cheers, Don.

Don1 said:

Hi Clarky,

Sorry for the delayed response. Originally I had all the balance turned to the passenger side as the drivers side speakers only hissed. I think I now get just the hiss from the drivers side with nothing from the passenger side. If I turn up the volume I eventually get a loud pop. I don't have access to the car presently to check any further. I guess I will have to start looking for a DSP amp.

Would there be any chance of testing on the DSP connector for an audio input using a headset or small speaker and wires to try to confirm the DSP is the problem before searching for one?

Click to expand...

Yes, that may work - the output level of the HU and the impedance would be suitable for headphones - that way you could check that the HU is sending each channel to the amp correctly and possibly rule it out - although I still have a sneaking suspicion your HU may be at fault. When the amps go, they tend to die completely - although it's not beyond the realms of possibility.

Was the sound from the driver's side speakers more of a hissy 'buzz' that maintained a constant volume? If it was, it suggests a HU or wiring fault. First thing to check would be that the plugs are still secure in the back of the HU - it's not unknown for them to come loose over time...

Hi Clarky,

The noise is a hiss at a constant volume that I think increases with the volume control. I won't have access to the vehicle for a week or so to check.
I removed and refitted the plugs and I did try a replacement H/U with no joy ( a really cheap unit removed from a Suzuki). When I get a chance I will study the rave diagrams and see if I can confirm an audio output from the H/U and an input to the DSP with headphones.