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      04-25-2012, 08:08 PM   #68
kaigoss69
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Drives: '08 335i
Join Date: Jul 2008
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Quote:
Originally Posted by E30 Racer
Quote:
Originally Posted by taibanl View Post
Why is the high level input, reportedly superior.
I'd be interested in the answer to this as well.

My HD600/4 has the same issues as reported above, but I've determined its an input signal issue (present even with the OE HiFi amp). The car is an E82 with HiFi + Technic harness adapter. Taking the front channels from the harness to the HD in conjunction with the low input setting (gains at min), I get noise. Switching to high voltage removes the noise but as mentioned above, it returns when the gains of the amp are turned up.

Recently I ran the front channels from the Technic harness into a Mosconi 6to8 DSP. This processor has low/high input settings as well. Interestingly, I ended up using a high voltage input configuration to the 6to8 and retained the low voltage setting at the input of the HD. Other combinations resulted in what sounded like a really compressed signal; very poor sound quality with an unnatural dynamic range.
One thing I don't like about the HD amps is the proximity of the power terminals to the RCA plugs. I found out that the noise was being picked up at the RCA plug from the ground wire that was running within 1/4" of the RCA plug. If you run the power wires and RCAs in opposite directions, there is no noise.
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Mobridge DA2 > JBL MS-8 > JL Audio HD600/4 > (3) Hybrid Audio L3SE & (2) Rainbow Cal25; JL Audio HD900/5 > (2) Morel HCW-10 & (1) IDMax 15
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