has the premium sound system got another HMA4045 amp contained inside the subwoofer as well as the dsp xqk100340 amp or not ?

I can't remember the part number of the sub amp, but yes it has a separate amplifier to the XQK100340.

The DSP amp processes the pre amplified subwoofer signal and then passes that back out to the subwoofer unit, which depending on model year has either a small black box amp on the outside of it, or a somewhat larger amplifier unit bolted onto the back of the speaker coils/magnets.

so could that the the reason i get no sound from the system rather than a dud xqk100340 amp ?
the head unit tunes into radio stations and recognises the cd player but i get no sound from the speakers or subwoofer

Not likely, the XQK100340 amp failing is somewhat of a common occurance and working ones are ridiculously expensive when they come up.
I've been working on a replacement solution and have something that works, but at the moment you lose the factory navigation audio, though integrating that is on the list.

The subwoofer will stop working with the XQK amp faulty aswell, as the signal goes from the head unit into the amp, where is gets adjusted as required for volume etc, before it is passed back out to the sub amplifier. So if the XQK amp is dead, then it won't be passing any audio through it and back out.

If you have factory navigation and it's faulty, then it can be worth trying to unplug the navigation computer in the loadspace too, as I have heard of occasions where the nav computer has failed and sent a permanent 'mute' signal to the XQK amp which has then cause all the audio to stop ((as if the navigation is talking - but it's not).

Unfortunately the most common cause is the XQK100340 amp though.

Thats what I thought - a bit of a long shot to think i could getaway with not having to replace the main amp.
Makes you wonder why they replaced a fairly reliable system with 5 seperate amps for an unreliable with with a single amp.
I just don't fancy the hassle of re-wiring to accommodate the previous system, especially as there wont be any plugs in the doors for the 4 seperate door amps system and also no plug for the 5th amp for the subwoofer.

I am guessing they replaced it as a part 'test' for the L322, as it uses the same kind of setup with a similar amp (but unfortunately they aren't compatible either ) That and as the RR's were starting to become more of a luxury vehicle by that time, they wanted to be able to market it as a 'premium' stereo option...

That being said, you don't need to rip all the wiring out and start again. As all the wiring for all the doors, and the feeds from the head unit end up in one place in the loadspace, you can fit amplifiers in there. The only extra thing you need to run is 2 pairs of signal wires for the rear left/right from the head unit, as the DSP system only uses a single left/right input, which the DSP amp then manipulates and outputs to all 4 doors.

I've been working on a replacement option and have documented where I've got to so far in this thread on Rangerovers.net:
http://www.rangerovers.net/forum/7-range-rover-mark-ii-p38/226218-dsp-amp-replacement-project.html

I have just managed to source what I believe are the correct connectors for the original door amps from a supplier in China, so in a month or so, I should have them and be able to make sure they are correct and be able to build amp replacement kits by the end of the year, if all goes well.

sounds good - i thought i had found one for 100 quid from a beakers in birmingham but turns out after he took the subwoofer out there was no amp behind it, It had the 5 amp system as it had the little amp on top of the subwoofer - doh