Brian... what amp(s) are you running? ... (archive)

I have been dealing w/the stock HU v.s. aftermarket amps issue for the past year w/varying success but have some very interesting findings. For example the fact that the stock head has clean pre-out signal but high output impedance (circa 50kOhm) and therefore will not work correctly w/the majority of aftermarket amplifiers due to the fact that they have ~10kOhm input impedance. Only a/d/s/ amps have 47kOhm input impedance, all others (that I am aware of) have 10kOhm. This mismatch will result (experimetally verified w/PPI and Alpine amps) in either excessive system hiss, and/or signal distortion at artificially low volume levels relative to the amplifier's power. The result... even w/mismatched input impedance is still mind blowingly better than the stock amp so the signal imperfections can sometimes be overlooked, but you WILL get hiss/distortion, except for the sub amp of course.

A way to correctly deal w/the input impedance mismatch problem in case you don't have an a/d/s/ amp is to get a signal processor (or something else) in between the HU and the amp, which will have sufficiently high input impedance for the head unit. For example a line driver or some other signal converter... There are currently three such processors that I am aware of: 1) Phoenix Gold PLD1 Line Driver (~$100), 2) Linear Power PA2 Audiopath Enhancer (~$450), 3) an unidentified gizmo/signal converter (~$40) (a'la Soundgate but different) my friend Chuck the car installer uses.

I personally have the a/d/s/ px/a amp and as such do not have the input impedance problem, but I have tried other amps with Chuck w/results outlined above. Chuck has also tried variety of configurations (mentioned above) w/premium and non premium E39 head units.

space :D

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here is how it goes.. Brian Lewis (00 540iA Sport) 14:00 4/09/2001 (0)

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