Originally Posted by scooby9
The reviews on the HD600/4 are very mixed over the web. Similar to PDX in that it is another D-class amplifier that can be used for duty other than just subs. I've been on a few audio forums and the consensus seems to be that the Slash V2 series is much better in terms of SQ. Maybe a 300/4v2 could be considered? These amps also take balanced inputs so you could use the same connectors as your PDX amp.
I agree with you, and for that reason I used my slash 300/2v2 to drive subs, and the PDX for front and rear channels and it almost did its job pretty well till the input sensitivity, the sound is very clear and precise. I didn't pick an another slash 300/4v2 because of its large size and high power consumption. The PDX fits wonderful into the place where the oem amp was. If the HD600/4 were not that over priced 800$ I would have already tried it. Its 8V min. (PDX 4V) input sensitivity may have halfed the hiss issue. Anyway, BMW should really improve the HU sound quality.
Now I recall VP Electricity mentioned the noise problem issue, he said the JL amps were just balanced input compatible but not the real balanced, it just took the half the input signal amplitude, so as to the alpine amps.
Maybe only the audiocontrol linedriver has the real balanced input?