Can somebody explain gain knobs to me?

[eli346 10+ year member]

I keep hearing all this stuff about the knob that comes with the amp. I've heard a bunch of different things about them so ive always just used the sub level on my HU to control it but it would be a lot faster to just the the knob. What does the knob actually control? and how should i be using it?

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[zako 10+ year member]

The gain knob is there for level matching your speakers with each other. If you set gain correctly, there will be little need to adjust subwoofer level from the head unit. However, if you level match the subwoofer with other speakers by ear, there may be a danger of setting the gain level so high that you overdrive either the subwoofer or amplifier. If you listen your music loud, you need to set the gain with a DMM. There is a tutorial right here:

http://www.caraudio.com/forums/car-audio-reference-database/534215-how-set-gains-dmm.html

I have skimmed though this tutorial, and want to add a couple of things.. first using a -5dB test tone, instead of -dB, may be a better idea because normal music normally doesn't reach above that. Even that bass content that reaches -5dB is often short lived. Second, you should investigate whether your head unit produces the max output rated unclipped voltage on the RCA outs with the "subwoofer level" setting at 0dB or at max. The tutorial suggests that the "max" should always be used, but I disagree. I measured with a DMM RCA out voltages on my Kenwood head unit, and it appears that they get close to 4V with subwoofer level at 0dB. I also tried to set gains by DMM using a Pioneed DEH-80PRS once. If the "subwoofer level" is significantly above 0dB, the amp goes into protect mode immediately. So be careful, if in doubt, I say leave it at 0dB. If that results in low voltage out, who cares? That's what amp's gain knob is for.

 

[2010HHRUMADBRUH 10+ year member]

Depends on the amp.

RF amps (Like my p500-2) use a knob that is literally a remote bass boost knob. It does not adjust gain.

I would suggest a pac LC-1 as such:

Head unit > sub outs > RCA > PAC LC-1 > RCA > SUB AMP

The pac lc1 is an RCA voltage adjuster that works with ANYTHING that uses RCA's. Your computer, home stereo, TV....you name it.

Forget buying those $25-$40 remote knobs *cough* sundown *cough* and just get one of these.

I bought one. I love it. Never looking back. The best part is that it works for amps that don't have a remote knob of sorts.

BTW I think the pac lc1 works as follows: will never output more than what your head unit is putting out.

So you set your gains as normal - EDIT - and have the pac LC-1 all the way up. That way the max setting on the pac lc-1 would never allow clipping. -thanks for clearing this up RicksI30

I got mine for $10 shipped lightly used on ebay. Very nice little device.

This one is new. $12.30 shipped Pac LC 1 Car Bass Amplifier Remote Level Control Knob | eBay

 

[RicksI30 10+ year member]

Depends on the amp.
RF amps (Like my p500-2) use a knob that is literally a remote bass boost knob. It does not adjust gain.

I would suggest a pac LC-1 as such:

Head unit > sub outs > RCA > PAC LC-1 > RCA > SUB AMP

The pac lc1 is an RCA voltage adjuster that works with ANYTHING that uses RCA's. Your computer, home stereo, TV....you name it.

Forget buying those $25-$40 remote knobs *cough* sundown *cough* and just get one of these.

I bought one. I love it. Never looking back. The best part is that it works for amps that don't have a remote knob of sorts.

BTW I think the pac lc1 works as follows: will never output more than what your head unit is putting out.

So you set your gains as normal or maybe a little high. No matter where the knob is on the pac lc1 it won't change anything. the max setting will be your max gain and like there is no knob. turning it down will limit the voltage to the amp and thus making it quieter. so maybe set the gain with the knob at half. loud songs - turn it down. quiet songs - turn it up. choice is yours.

I got mine for $10 shipped lightly used on ebay. Very nice little device.

This one is new. $12.30 shipped Pac LC 1 Car Bass Amplifier Remote Level Control Knob | eBay

You need to set the gain with the knob all of the way up.

 

[2010HHRUMADBRUH 10+ year member]

You need to set the gain with the knob all of the way up.

Hmm. Yeah I guess that would make sense. Then you would just turn it down to begin with and the LC-1's max setting would always have a clean output? Didn't even think of that. Thanks for adding that.

 

[RicksI30 10+ year member]

Hmm. Yeah I guess that would make sense. Then you would just turn it down to begin with and the LC-1's max setting would always have a clean output? Didn't even think of that. Thanks for adding that.

Let me try to explain this (I have had a few beers). Lets say you have a 4v pre out head unit and you set your gain with the knob half way up (~2v) and then you turn your knob up to 100%. At 100% the amp is now seeing a ~4v signal and your gain is set too high, thus clipping and overpowering your sub.

Make sense?

 

[2010HHRUMADBRUH 10+ year member]

Let me try to explain this (I have had a few beers). Lets say you have a 4v pre out head unit and you set your gain with the knob half way up (~2v) and then you turn your knob up to 100%. At 100% the amp is now seeing a ~4v signal and your gain is set too high, thus clipping and overpowering your sub.
Make sense?

Yes I know exactly what you mean //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I got some close ups of the guts. Don't have anything to take the front nut off, unfortunately.

You can turn the mounting part over to mount to something under-neath if you like.

Also looks like you could simply just use the nut and cap (knob) without the faceplate and mount almost anywhere on the dash. That's probably what I'm going to do.

Also: you can take the mounting base off and it has a little square box with enough coverage on each side to over a hole you make, so if you have a flat area you can simply cut it out and pop this in.

TL:dr you aren't limited to mounting this with 2 screws!

 

[eli346 10+ year member]

Now that I messed with it some I'm pretty sure it'll work fine. My gain on the amp is set to halfway up so when I turn the knob up it keeps getting louder until it gets to the halfway point right about where my amp gain is set and when I turn it past halfway it doesn't turn up anymore so the amp gain is the main one and the knob only controls from zero to where my amp gain is set.