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03-08-2009, 01:27 PM | #1 |
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Guys with aftermarket amps, how did you set your gains?
Since the OEM HU does not have a volume level display, how do you set the volume so you can set the input gains on your amps. Do you just crank it all the way up assuming eventually it gets to max and set it that way or do you crank it all the way up and then down a few clicks before you set it?
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03-08-2009, 01:44 PM | #2 | |
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For example, for a base analog OEM system I don't use a direct to amps/processor connection, I use a line driver at the OEM HU/Nav outputs first, then to the aftermarket processors/amp and that's what I adjust for the best signal to noise ratio. That's what I did in my E46 M3 Harman Kardon OEM system, no hiss at all. In the case of my current Premium setup, because of the issues of the bit one high level inputs being saturated with the OEM amp, I was forced to adjust only the underseat subs amp gain because I have to reduce a lot of the input level of the processor to avoid the saturation. At least the OEM mids and tweets amp gain can remain at minimum, so hiss is almost non-existent. However, once the digital preamp device shows up then I will be able to set the bit one built in line driver to its maximum levels and set all my amps gains to minimum. |
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03-08-2009, 04:15 PM | #3 | |
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03-08-2009, 04:32 PM | #4 |
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If you just have an amplifier with no processors, you can just turn your system on, turn the volume down on the head unit and adjust the gains to where you can hear hiss and then turn it down so you don't hear any hiss. It's been several months since I set mine and I'll double-check but I think the head unit puts out a fairly nice line voltage so you don't have to turn the gains up too much. The area where I had to adjust is the front/rear levels because the OEM speakers I left in the back were much more efficient.
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03-08-2009, 05:03 PM | #5 | |
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Your max volume (because there is no way of measuring that in our OEM systems) is set by you, so it can be higher or lower than mine. In my case I just play certain bass notes or certain heavy bass songs and crank the volume up to a level that I consider enough and then I listen for any pops/distortion. If any pop is heard then I lower the gain until I don't hear it any more. With a processor this can be done in too many ways, output level, EQ or even crossover type and not adjust the gains at all at any volume. So there is no one single correct way of adjusting gains. Regardless of using a processor/line driver or not, the amp gains are normally adjusted either based on how high you can turn the volume up without distortion (by ear) and then adjusting the gains to just below that distortion threshold or by following the JL Audio more technical process of measuring amp output voltages (page 10, http://mobile.jlaudio.com/pdfs/14997.pdf). The great thing about the BMW OEM HU/CCC/CIC is that the analog outputs are 5V differential. So it could be possible to just leave the gains at minimum if those outputs are connected directly to an amp that have a max input level in the 4-5V range. |
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03-08-2009, 05:38 PM | #6 | |
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03-08-2009, 07:55 PM | #7 | |
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03-08-2009, 08:06 PM | #8 | |
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I've never used a DSP with a built in line driver so I've never actually used one of these indicators. The only DSP I ever used was the Alpine H701. The amps that I was looking at that started this whole thing was the Kenwood Excelon X4R. Built in DSP with clipping indicators but I'm starting to think that only the crossovers would be useful because the parametric EQ bands are not really infinitely adjustable. So I would probably end up getting an outboard EQ anyway.
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