Setting Gains

Marv,

What is the proper procdure for setting the gains on an amplifier?

 

the way I have always done it is turn the head unit up to about 75% then turn your gain up until you begin to hear distortion then turn it down just a little. just the way I have done it.

 

The above will work and there there are several other ways to do it a bit more accurately depending on what kind of test gear you have available. I made a post on it somewhere but I can't find it right now so I will post it again as soon as I have a few minutes today.

 

That's how I do it.

 

Thanks Marv,

I know I have seen it before somewhere on here. I spent 2 hours last night searching for it but could not find it either.

This is for my boat, I still have to order a box from you later in November.

THANKS!

 

It appears I posted this on another forum which is the reason I couldn't find it here so I copy/pasted and edited it below.

There are numerous ways to set gains however I find these methods pretty easy for most to do without requiring expensive test equipment.

Ideally you would like to have the "hottest" unclipped signal up front and the gains as low as possible to keep the noise floor down. Generally speaking most headunits I have tested clip around 75-80% of max volume however if you want to find out exactly where your headunit clips all you need is a 1khz 0db test tone and a self amplified computer speaker. Connect the self amplified speaker to the headunit, play the 1khz tone and turn the volume up until you hear a sudden change/volume increase in the tone which will be the point it clips. Also, be sure to set the computer speaker volume low so you are not clipping the amp in there and set eq's etc to flat. In either case record/remember this number as that is the highest you will want to turn the volume up.

To set the gains on your amplifiers you will need to download some test tones as follows..
1khz 0db
1khz -3db
1khz -6db

50hz 0db
50hz -3db
50hz -6db.

Depending on the actual output of the amplifier as well as the power handling capabilities of the speaker(s) you may find it beneficial to purposely clip the amp with the -3db or -6db tone in order to "squeeze" some extra power from the amp.

Procedure for front/rear speakers:

1. turn gain/sensitivity knob on amps all the way down
2. make sure all eq's etc are set flat
3. insert the disc with the appropriate 1khz test tone and pause it
4. if you used the computer speaker to find the clipping level of the headunit set the volume to that level and if not set the volume to approximately 75-80% of maximum
5. un pause the headunit and slowly turn the gain knob up until you hear the sound change pitch/suddenly increase in volume and then back the knob off slightly***this will create a VERY loud high pitched sound so you may not want to do it in the middle of the night!***.
6. repeat for rear channels if applicable

For the sub amp I use a little different method that requires a cheap Piezo tweeter from Radio Shack (about 5 bucks) and the 50hz tone.

1. Wire the Piezo to the amp in parallel with your sub(s) (due to the design of a piezo tweeter it will not change the load on your amp)
2. turn gain/sensitivity knob on amps all the way down
3. turn off all bass boost/eq's etc
4. insert disc with appropriate 50hz test tone and pause it
5. set your sub level control to max and the main volume as instructed above
6. un pause the headunit and slowly turn the gain knob up until the Piezo starts to make a sound and back it off a little.(due to it's design the Piezo will not make any sound until the amp clips)

A couple of things to note...clipping increases the high frequency content in the signal so it can bypass the crossover protection on some components and possibly damage the tweeter (please see FAQ's stickied at the top of the Audio Forum for more on clipping). Also there is no such thing as a "perfect" gain setting since music is dynamic and recorded at different levels from source to source and even song to song on the same cd in some cases! In any case I always use my ears to keep from damaging speakers when playing music loud...if a speaker sounds "distressed" or makes a "popping" sound turn it down!

BTW, there is more to it than this as well as other ways to do it so feel free to ask questions if I missed something you'd like to know!