Re: Mysteries of the "premium" DSP / AMP (archive)

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This basically tells us that the Stage 1 is about as far as you can inexpensively take the upgrade path. Jim's method of tapping off the output of the D/A converters directly will yield the best signal, but with a suitable balanced to unbalanced converter, tapping off the subwoofer speaker output will work OK too. BTW, If you are using a P4100 in your upgrade, you will not need the balance to unbalanced converter, just leave the switch on the P4100 in "Balanced" mode.
The modified "level 2" step with the DSP system is adding upgrade amplification to the factory speakers. The reason for keeping the factory speakers is that the DSP generated crossover settings will not be able to be altered for any new speakers you would add. Fortunately, the mid/high range speakers are not too bad. The 5-1/4" midbass speakers could use some improvement. Upgrading the amps are a viable way to improve performance since most of the the distortion of the built-in BMW amps will virtually go away once it is not driving a loudspeaker load. There are some logical limits to how to do this. First, you'd want to do the whole front, or whole rear system together. Personally, I'd just do the front and leave the rear on the BMW amp. Secondly, since you need 6-channels of amplification for the front, use a single 6-channel amp. Using multiple 2-channel amps is simply asking for ground-loop related noise problems. A P640 would work well here. Finally, the balanced to unbalanced converter used should have a load impedance higher than 100 Ohms. If it is one of those converters which tries to simulate a speaker load (about 50% of the ones I've seen do), then you do not get any distortion reduction benefit since the BMW amp will think it's still connected to speakers. With a proper high impedance converter, the distortion of the chip in the BMW amp will dramatically reduce. Not as much as with a real preamp output, but enough to make a real improvement in the sound with the new amp.

: I am having my a/d/s stage one upgrade installed next week. Can I put any of this new found information to good use? Are there any special instructions that I should give to the installer?

: Your thoughts would be greatly appreciated. And, Jim L, thanks for an amazing post.

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