E38 Afternarket AMP downgrade.

[Jimakaze 11]

All good things must come to an end over the new year break I removed my 2 Pioneer 4 channel amps from.my E38 and installed them in my sons Passat (all 8 speakers in the doors upgraded). 

This meant no sound in the E38. As I had never got arround to upgrading the rear door speakers I reconnected the rear speaker signal from the radio to the X605 connector, and reconnected the rear speakers to the X606 connector. All worked fine so last weekend I installed 2 Sony 2 way amps and an SSL active crossover. 

This is where I hit trouble. When I power on the car all the speakers are playing and it sounds great - for about 5 seconds - then the front speakers and subs stop making sound. 

I connected my phone using an aux cord to the input of the SSL active cross over and the crossover and amps are working perfectly. 

So I am faced with sone cutout operating in the BMW radio unit. I must admit being a little bemused. It work perfectly with all aftermarket amps, or all OEM amps, but not 1/2 and 1/2. 

Tomorrow I will diconnect the X605 connector taking the OEM amp out of the equation and try connecting the radio output signal back into the active cross over. 

The only thing I can think of is it is detecting some impedance mismatch and a protection circuit is activating. Fun for the weekend.

If anyone know any tips I'd love to hear them. I'm not keen on pulling everything out to eyeball the radio hidden as it is behind the amp. 

Jim

[Olaf 3317]

@Neal or @kulgan - got any ideas?

[Neal 544]

BM tuner will shutdown on low voltage ( 10.8 from memory) could be cause. Check voltage

Tell us more about how the Sony amp is hooked up. Most mid stream Sony amps only expect unbalanced inputs. Factory tuner will be sending differential audio at plus and minus 4.2 volts. It could be either the Sony amps shutting down the input stage or the tuner doing the same.

would almost worth trying connecting the tuner to the high level Sony inputs to see if the behaviour changes.

this is about all I can think of now that could cause this behaviour.

[Neal 544]

Picture would be good

[kulgan 1042]

The radio modules on E38s get dry joints and if it's toast will cause this problem. I've had a couple of E38's with sound that will cut out after 30 secs to a couple of minutes both caused by faulty radio modules. Alternately the Amps also have this problem but it's usually signalled by static and a lack of volume.

Good luck and let us know how you get on.

[Jimakaze 11]

Thanks for the ideas.

Turns out the output from rhe BMW radio is amplified / hi level. This was overloading the SSL pre-amp active crossover, and the Sony amps when connected directly. 

I sourced a high level to RCA adapter for $18 from Jaycar. Wired it in and its all now working. 

Only problem is that the Sony Amp doesn't drive the Kicker subs hard enough. I am going to bridge the output and drive 1 sub as this may sound better.

Should have left my nice Pioneer amps in place and given my son the two Sony 2 channel speakers.

If that works ok I will source a higher powered amp.

Jim

Edited April 24, 2017 by Jimakaze