bmw 530i digital noise blaupunkt amp

I have a 2003 BMW 530i with Nav but non-DSP. I recently took the multiple (one for the mains and one for the sub) Alpine amps out of my car and am now trying to install a Blaupunkt THA-555PnP amp to consolidate the mains and sub all under one amp. I am having a problem where once everything is hooked up the amp powers up but I just get electronic noise through the speakers.

This is with the car off - not alternator noise. It sounds like electronic communication as if it was from a fax or modem - perhaps ibus signals. If I play with the volume I can hear clicking as I turn the volume up or down. I get no audio material whatsoever though through the stereo through any channel.

I am plugging directly into the 26-pin connector with a male 26-pin connector I have. The pins are on pre-made OEM BMW leads with the correct pins. This goes to a 12-pin molex connector (of which 8 pins are used) which connects to a set of twisted pair RCA cables. I have checked continuity on all of the leads and they are fine. Pin layout I am using are #'s 1, 2, 3, 4 for RR-, RR+, LR+, LR- and 14, 15, 16, 17 for RF-, RF+, RF+, RF-. I know these are the correct pin outs. I had also tested this cable on the old Alpine MRVF545 amp I had and it was fine so I am at a loss here.

Anyone have any suggestions as to where to start to fix this problem?

Anybody got any thoughts on this?

I went out and borrowed an Alpine 4-channel amp and leaving all of the wiring as is plugged it in and that worked fine - so I know that there is no problem with my wiring. Plugged the Blaupunkt back in and no joy. I had Crutchfield swap out the Blaupunkt and got that today. Plugged the new amp in and just like the first one was just getting the digital noise through the system - still no joy.

Could this have something to do with the Blaupunkt maybe not being able to accept the (what I understand are) balanced outputs of the BMW head unit? The three Alpine amps I have tried have all worked fine. I had also tried an a/d/s p840.2 and had the same problem as I am having with the Blaupunkts.

The Blaupunkt has what they call their PnP input. I found out yesterday that if I use the RCA input I have to have a separate sub input to drive the sub channel but if the PnP input is used then it will derive the sub channel from the front/rear there. However, the PnP input is only usable with a special cable that they of course don't make for US spec BMWs.

I hoping someone has some thoughts on this. The next step is to try the new Infinity Kappa Five 5 channel amp that is spec'd to accept balanced inputs.