Help with setting gains on amp

[Astyl 10+ year member]

Hey guys, Ive got a Alpine 9851 Headunit, it has 2 volt Pre outs, and im hooking it up to a 4 Channel Alpine Amp that puts out 40 Watts RMS , now ive heard people say to go easy on the gains so you dont clip, does that mean i shouldent ever turn my gains past halfway? Or do i just play a test tone and keep crankin it up till i hear it start to distort, even if thats all the way up, and hope thats good?

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[SAG3 5,000+ posts]

check out the gain setting tutorial

 

[SAG3 5,000+ posts]

here

 

[Astyl 10+ year member]

maybe im a retard but i dont understand those formulas whatsoever... and im not tuning a subwoofer, this is just for regular cabin speakers off a 4 channel amp

 

[SAG3 5,000+ posts]

doesnt matter, if you want a non clipped signal keep it low or set it correctly.

 

[Astyl 10+ year member]

Well the speakers are 4 ohm ( obviously ) , my amp is 40 watts RMS, and my headunit will be tuned at volume 20 and has 2 volt preouts... what do i do?

 

[El Ropo 10+ year member]

Well the speakers are 4 ohm ( obviously ) , my amp is 40 watts RMS, and my headunit will be tuned at volume 20 and has 2 volt preouts... what do i do?

Step 1: Take the square root of (40 x 4), which is 12.65 volts AC, not DC.

Step 2: Go download the 1kz 0db test tone from realm of excursion

Link: http://www.realmofexcursion.com/audio/1khz.mp3

Step 3: Burn the test tone file to a blank cd.

Step 4: Follow gain setting tutorial to play the test tone in your car, and set gain to approximately 12.65 volts per channel, and you are in business.

Important facts:

NCH tone generator does not create 0db test tones, they're more like -12db (very quiet, causing you to set gains way too high).

The best way to set the gains with a DMM is to plug DMM right into a single channel of the speaker outputs, matching + with +, and - with -. (this means disconnect the speaker wires from the amp)

Be sure to use the volts AC setting on the DMM, as many autosensing DMMs won't automatically switch to AC from the default DC.

If you don't feel comfortable doing any of this, then I'd suggest you pay a shop to do it for you (not CC or BB, a real shop). If you ask a person at the shop about setting gains with a DMM, and they don't know what you're talking about, run away as fast as you can //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

**Edit** One more thing, be sure to disconnect the power supply to the amp while removing speaker wire, and inserting DMM probes into the amp. This will help you avoid little problems such as releasing the magic smoke from the amp Also remember that if you have a capacitor in the system, it will still hold juice and has the potential to harm the amp even if the battery connection is removed. This means you really should either disconnect the cap from the system when disconnecting battery, or you could simply disco battery lead (from battery to cap), then press on the brake pedal of the car for 15 seconds or so, till all juice is drained from the cap.

 

[Astyl 10+ year member]

so all i gotta do is put a DMM were the speakers hook up and keep turning up the gain on the amp till i get 12.65 V , while playing a test tone at max volume that ide run my system at daily?

 

[bimma85 5,000+ posts]

so all i gotta do is put a DMM were the speakers hook up and keep turning up the gain on the amp till i get 12.65 V , while playing a test tone at max volume that ide run my system at daily?

You got it, assuming your amp will do 40@ 4 ohms //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif. 40w*4ohms=160 sqrt(160)=12.65

 

[Astyl 10+ year member]

It says it does, so im hoping thats what it'll do

http://www.crutchfield.com/S-P1c63OWuZE2/cgi-bin/ProdView.asp?search=Alpine+Amp&i=500MRPF250

 

[Cris 10+ year member]

It says it does, so im hoping thats what it'll do
http://www.crutchfield.com/S-P1c63OWuZE2/cgi-bin/ProdView.asp?search=Alpine+Amp&i=500MRPF250

it'll do it, no worries. What you have to worry about is oversetting the gains, meaning that your amp is overexerting itself. When you overset your gains, you're actually getting more than the rated power... say, 60 watts rms per channel for your amp.. but you're doing it at increased thermal temperature, strained components, and much higher distortion rates... which are dangerous to amps AND speakers.

 

[Astyl 10+ year member]

So should i go easy on the gains still?

Like say i get the 12.65 Volts that im supost to get, but thats at like max gain, should i still let off

 

[El Ropo 10+ year member]

Be sure the subwoofer volume control on your alpine HU is set to +15, or whatever the highest setting is.

The recent models of alpine HUs are notorious for having very weak voltage to the sub out unless it's cranked up all the way.

Maybe other alpine users can comment on what exact volume level their pre-outs start to clip at. With that info, you would know what number on the dial is a safe number to set gains at. for example, on my Kenwood x889, I set them at volume level 27 out of 35 (just over 75%) And I generally listen to music at volumes 19 to 26, maybe up to 30 on super quiet recordings.

 

[Astyl 10+ year member]

yeah, the max volume on mine is 35, and i usually listen to stuff at 18, sometimes 20 max , i know it can go alot higher, but i dont have the need too

 

[Cris 10+ year member]

So should i go easy on the gains still?
Like say i get the 12.65 Volts that im supost to get, but thats at like max gain, should i still let off

If you're getting 12.65 volts out of the amp and your HU is near where you want it to be (say, 20 out of 30) then you're theoretically fine. Set your HU how you want it set... bass levels where you like them, treble where you want them.. and achieve a 12.65 out of your amp. When you do, you have the correct gain setting.

As for where you set it at, around 75-80% of max volume is recommendable. I wouldn't do something as low as 20 out of 35. That's around.. what.. 60%?