Amp gain question

[Vincer77 10+ year member]

I am running two 300 rms subs from a single 400 w rms amp channel. Is it ok to run maximum gain, or should I run less due to distortion/ clipping. Is there a max percentage rule of thumb?

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[MOFOMAN 10+ year member]

i took my amp into a shop to get it all dialed in they ended up charging me 5 bucks.. only thing i couldn't do myself

 

[NASTY08IMPALA 5,000+ posts]

Gain is not a volume knob ...u want to match the output of ur rcas to the voltage on the amp

 

[Kastlez_ 10+ year member]

Gain is not a volume knob ...u want to match the output of ur rcas to the voltage on the amp

This!

There is a simple procedure to "help" assist you to setup your gains and that's using a DMM aka digital multimeter. Google it or YouTube

 

[MOFOMAN 10+ year member]

alot simpler an alot cheaper to just take it in

 

[Beatin' 10+ year member]

setting your gain with a DMM and test tone cd is so stupid easy.

Make sure the subs are unhooked. Play a 0db or -3db 50-60hz tone and turn up the volume on the head unit to the max position where you would usually listen to music. Mine goes up to 50 so I like to tune at 30/50 instead. For you it could be a different range.

While the tone is playing at which ever range on your HU you choose, set your DMM to AC voltage, usually at the lowest setting that reads up to 200volts. Then put the test leads on the speaker terminals on your amp and turn up the gain until you see the correct voltage reading for the ohm load your sub will let the amp "see". Then, your done! Shut everything off and hook up the subs.

by the way, what is the final impedance of the subs? The amp can send out 400wrms at what ohm load? I don't think we can figue out the target voltage reading on the DMM if we don't know the impedance of the subs and the ohm load the amp can deliver 400wrms to.

 

[Vincer77 10+ year member]

The amp is rated at 400 w rms at 2 ohms. Subs are wired at 2 ohms. Since the subs have much more capacity than the amp can put out, I should theoretically not see the calculated volts based on subs rating. So the question is, will max gain on amp cause any problems?

 

[NASTY08IMPALA 5,000+ posts]

The amp is rated at 400 w rms at 2 ohms. Subs are wired at 2 ohms. Since the subs have much more capacity than the amp can put out, I should theoretically not see the calculated volts based on subs rating. So the question is, will max gain on amp cause any problems?

u cant crank the gain on any amp no matter how.underpowered or overpowered ...listen to what has been told

 

[juanmgarza26 10+ year member]

The amp is rated at 400 w rms at 2 ohms. Subs are wired at 2 ohms. Since the subs have much more capacity than the amp can put out, I should theoretically not see the calculated volts based on subs rating. So the question is, will max gain on amp cause any problems?

your amp is rated for 400 and anything below, if you crank the gain to where you want more than 400 you are going to start clipping and damage your sub, this has happened to me before... listen to what everyone is telling you

 

[Beatin' 10+ year member]

The amp is rated at 400 w rms at 2 ohms. Subs are wired at 2 ohms. Since the subs have much more capacity than the amp can put out, I should theoretically not see the calculated volts based on subs rating. So the question is, will max gain on amp cause any problems?

The gain is not a volume control. You don't put it on minimum or maximum. It's 99% of the time going to have to be put somewhere in the middle. 400wrms at 2 ohms means you must turn the gain up until you see the DMM read around 28.3volts at the max level that you like to turn the HU to.

 

[vnzvnnsz]

C?m on bÃ*i vi?t r?t hay up cho b?n

 

[maylar 10+ year member]

The amp is rated at 400 w rms at 2 ohms. Subs are wired at 2 ohms. Since the subs have much more capacity than the amp can put out, I should theoretically not see the calculated volts based on subs rating. So the question is, will max gain on amp cause any problems?

The amp doesn't put out its max power at max gain. It's not that simple. You need to adjust the amp for undistorted 400 watts.

 

[MOFOMAN 10+ year member]

if you dont have your amp set up right they will destroy your subs.. having you amp tuned is alot cheaper then replacing your subs

 

[Vincer77 10+ year member]

Thank you for helping me understand this. This link explains it pretty well:

Amplifier Gain Controls

So if I am understanding correctly, my sub amp channel gain knob is marked .25 v to 5V meaning that when set at 5V, a 5V signal will max the output of the amp. My HU RCAs are 0 to 4 V. Setting the HU to 75% of max is therefore 3V, so theoretically, the knob should be set at 3V, so that the 3V will deliver the full power of the amp. The amp gain will actually be G = 28.3/4= 7.1.

Now, my front channel speakers that are rated for 70W rms. The front channel of my amp is rated for 125 W rms, so the gain should be set for 3 x 125/70 = 5.3V. Oops, it appears that even with the amp gain turned all the way down (.e. 5V), that I run the risk of overpowering those speakers. 5V setting will actually send 3/5*125 = 75W rms. But this is where impedance rise saves the day - right?

It will be interesting to see where these actually end up.

 

[Vincer77 10+ year member]

Well, I guess my last post was a bunch of c%$^. The sub channel worked as thought. The other channels did not. No problem dropping the gain on the front speakers.

I did notice that the right channel read about .4 V higher than right. Balance control on the HU was at zero. Is there normally an offset like that?