amp gain confusion..
 

I am really confused about setting gains and the proper way to do it. The 'textbook' way is to turn everything on your amp down, then turn your hu volume until it starts to distort, then turn it down a little. Then set your amp gain by turning it up until the subs distort then turn back a tad.

But it's gets REALLY loud when you do it and I think i might become deaf after adjusting everything :) In fact when it gets that loud, I can't really tell whether the signal is distorted or not.

Is there a better (easier on the ear) way to do it? I've recently added a 4 ch amp to drive my door speakers. For now, the gain on my amp is almost minimum and I just turn my HU volume to like 3/4 and it's loud enuff already (no distortion). But something tells me that this is not the 'optimal' setting.

But then my 'theory' is that i should pump as much RCA voltage signal to the amp (before distortion) so that it'll be less noise sensitive.

text book way is correct... just go deaf its worth it..
________
POT

If it's loud enough for you, don't touch it anymore ...

That's not an obligation to crank your gain to it's maximum, in fact gain is to ajust from different voltage you HU might send down the RCA... Some HU send 1.5V and high end one might send 5V or more.

On some amp the gain is rated with voltage on it ... so you check the spect of you HU voltage and you set the same thing on you amp.

When I ajust mine, I set the front speakers amp (don't have rear speakers, I always sit front anyways) and then I set the sub amp to get a good match between the two, you don't want to hear only the sub and almost nothing in front (some stupid "kid" do that to impress, the only thing you hear is BASS).

By setting your gain a bit lower the max spec of you amp is a good thing, that way your amp will not ending in clipping and that way it will save your speakers, sending DC to your speakers will kill them. After that you will only have to check to not make your HU clip.

I suggest putting a "pot" on your sub amp, that way you'll be able to raise or lower the bass, some CD have a lot of bass on it and some other CD doesn't have enough, so you can ajust between the two to always get a really good song.

The "pot" (read potentiometer) will need to be dual, you will need two RCA cable going to your trunk, one for the front amp and one for the sub amp.

cut the RCA going to the sub to solder the pot, if you don't have two output on you HU use splitters.

I have almost the same thing, but the pot is on my EQ (Phoenix Gold). Some other EQ have the same feature, even if they are DIN mountable or trunk mountable.

Note : If you make you sound pass though a pot make sure to get a really good pot, a good pot will be almost transparent.

Good luck!

Headunit voltage is mostly overated, I have a $700 dolaar alpine that claims 4 volts but wihtout distortion in only hits 2. The absolute best way to set gain is with an occisilscope to check both voltage and clipping of the head unit then to match it at the amp.

Megamind is dead on saying that gain is just a match on an amplifier for your head units voltage. Gain adjust the ratio of amplification. put in too much gain and the amp is asked to drive the speakers with more power than its capable of which is refered to as saturation. This is when the signal clips like hell ie distortion.

Amplifier Gain Controls:
Contrary to popular belief, an amplifiers gain control does not determine the maximum power that an amplifier can produce. As long as the preamp/drive signal has sufficient level, the amplifier will produce its maximum power output level. The gain controls are used to match the amplifer's gain to the gain of the other amplifiers in the system (in the case of a multi-amp system). The gain controls also allow you to match the amplifier(s) to the head unit. Not all head units have the same maximum preamp output voltage. Some head units are capable of producing 9 vrms out while others are only capable of 1.5 vrms out.

Please note that a head unit will reach its maximum output level (clipping) well before the volume control reaches the upper end of its range (usually at a point of 85-90% of its maximum range). This is especially true of tape decks, not because the audio section is of lesser quality but because some tapes are recorded at lower levels than others and the manufacturer must design the deck to be able to produce a sufficient output level with virtually any tape.

SOURCE : http://www.eatel.net/~amptech/elecdisc/gaincon2.htm

MageMinds

Agreed :)

Hi

I agree totally to before said things, BUT
it is a problem to get a stereo pot which has
exactly the same R on both lines. If you get one
then it'll be extremely expensive. Also you have to use a potential divider in this pot to not getting a 0 Ohm R to your RCA output.

The other thing is (which I also use) if you don't have amped rear speakers you can use the rear RCA output for the sub and regulate the gain of the amp using the front-rear fader of the HU.
That works fine if you stay in one area (front or rear). I mean you have to choose a position of the gain, where you only use the fron area or only the rear area to get smaller steps for fading. You know what I mean ?

Thanks for the suggestions! I totally understand that the amp will pump out it's designed wattage (xxx Watts RMS) regardless of the gain settings.

Yeah, my sub amp has a remote gain, so i can adjust the bass for every song/CD. I find that very useful. Previously i've used the Front/Rear fading method like HorstF said and it works okay.

The only thing i'm still unsure is that i can stick with my current gain settings. i.e. HU around 3/4 and amp gains to minimum.

OR

Turn down the vol on the HU like 1/2 or so and turn up the gain on the amp so it has the same loudness.

Which way you guys prefer?