Headunit subwoofer level output VS amplifier gain

[Golitan11]

I have a Pioneer DEH-X7500S headunit (4V preouts), an Hifonics BRX1100.1D and a Sundown SA-12 D2. I was wondering what is better to set your gain right:

1. Turn the subwoofer level output up on the headunit (maximum for example, which is +6 in my case) to use the full potential of your 4V preouts and minimize the amplifier work (lower gain), and then adjust the gain from that to match the desired voltage with a DMM (28-30V in my case).

or

2. Keep the subwoofer level output on the headunit at 0 and turn up the gain on the amplifier (higher than option 1 for sure) to match the desired voltage with a DMM (28-30V in my case).

[Golitan11]

I just tried to get the voltage coming off the RCA's (subwoofer preamps) with my DMM at full volume (speakers off for sure) with a 50 hz test tone (no EQ or filter) and I got 1.8V each with the subwoofer output level set to +6 (maximum) and 1.2V each with the subwoofer output level set to 0. I am a bit confused with this since they are suppose to produce 4V. Why do I get those numbers? Is 1.8V too high? Thanks.

[TheMonolith2001]

Okay I have a different head unit than you but it is pioneer and may act the same way. What volume are you at by the way?

When I move my volume from 61/62 to 62/62 it jumps an entire volt. I think pioneer rates their preout voltage at max volume with max sub out/etc volume as well. On your particular head unit this may not necessarily be a clean signal, so you may not really be able to ever get that high. That's fine though because this is what your gain is for, matching your amp to your headunit. I know higher pre/lower gain is better, but there probably isn't going to be a massive difference in gain going from 1.2v to 1.8v. Someone correct me if I am wrong though, I have never used a hifonics amp. If you REALLY want more pre-out volts get yourself a line driver. I would recommend AudioControl. The stuff they make is worth the price, and you can probably get a good deal on a used one. If you need a crossover or anything like that they make those as well with built in line drivers.

If I was in your position, I would set it up with the max overall volume that it plays clean, and the subwoofer at 0. This should minimize distortion which is going to make everything sound better. Is 1.8v too high? well it depends on your amp, check the manual to see what kind of RCA voltage your amp accepts. It probably isn't too high though.