Setting your Amplifiers Gain with DMM
 

Three things are needed to accurately set your gain on your amplifier using a digital multi-meter. This is a great way to set your gain so you are not sending a clipped signal to your speakers.

First thing - Decent DMM with ability to test for AC current.
Second thing - Test tone CD or CD with 50 hz multiple times on it.(easiest way is to just download it a bunch of times, or just copy it in the folder on your PC.
Third thing is your amplifier output voltage you can calculate it here on this easy calculator. All you need is the power (RMS) that your amplifier puts out, and the reistance at shich it does it. ex. 500 watts at 2 ohms
Amp output voltage calculator



Set all of your Head Units contols to zero,(like bass, treble, any bass enhancements)
Turn your gain on your amplifer down to zero.

Set your DMM to AC
Connect your DMM to speaker outputs on the Amplifier (using + and - terminals on your amp and your DMM)
Put the Test tone cd in your HU and turn to 3/4 volume (or about as loud as you will listen to it.)
Now turn your gain up slowly until you reach your output voltage found earlier.

If you want to add those bass enhancements and such, when you find your correct gain setting, turn it back down some, that way you do not send unclean power to your amp and then onto your speakers.

If you have any questions on this, please PM me

RE: Setting your Amplifiers Gain with DMM
 

I smell a sticky.

RE: Setting your Amplifiers Gain with DMM
 

Agree, however depending on what type of amp you'retrying to accuratelyto set the gains for you will need diffrent hz testing tracks.

RE: Setting your Amplifiers Gain with DMM
 

very ture. a 50hz tone will only work for sub amps. I like to use pink noise. That way, all amps are covered by the same track.

RE: Setting your Amplifiers Gain with DMM
 

can somebody explain GAIN to me? logarithms have never been my strong point so decibels are also a little troubling.

according to the calc above, i need an output voltage of 37.8V. when i listen to my music, i usually use the preset eq's and im almost always using "superbass" "powerful" or "vocal". if i set the gain at a flat eq with no bass enhancements, what will it sound like when i change the headunit controls? can it hurt the amp?

also, my amp came with a "bass control" knob. what exactly does it control? is it just a master volume control for the amp or dose it have anything to do with gain?


thanks for any help. im trying not to annoy you with all of my noob questions about this kind of stuff but i always try and research and understand everything before actually doing it :D

RE: Setting your Amplifiers Gain with DMM
 

bump

i dont think anyone saw my post. it doesnt seem like new messages show up on sticky threads

RE: Setting your Amplifiers Gain with DMM
 

ah, I just saw this.

here is a pretty good explanation on gain.

http://www.bcae1.com/gaincon2.htm

What you are doing with adding bass eq's and such is sending dirty signal to your amp. I wish that I could disable all eq functions on a customers car, because, then they cannot blow their sub. The knob depends on the amp. some are a remote gain, meaning that it changes the input, bad

Most these days are just a bassknob. Turn it up, it will max out tot he point that your gain on the amp is set. Turn it down, basslevel decreases, but the amp setting stay the same.

RE: Setting your Amplifiers Gain with DMM
 

thanks, that link cleared up a lot of info. so you think i should leave all of the bass/amp controls alone? i dont always want to listen to thundering bass. sometimes i just want to listen to my music normally, what should i do in this case? normally i would change it to "vocal" mode ( less bass, higher mids and sorta high tweets). but if changing the eq can be harmful to the amp ill try not to do it

RE: Setting your Amplifiers Gain with DMM
 

ther is more to it then that if u want to get really tech happy. get an O scope and test for a clean signal on the head unit for the max volume with a clean signal. then disconect the speakers hook up the Oscope to the amp and with the headunit set to the max clean output scope the amp turning it up till the signal is dirty then back it down till its clean then check the voltage on the amp. remember the max volume on the head unit and the voltage out put on the amp. thats the way mine is set up and when u run alot of power a clean signal is definatly a requirement. the gain on an amp is just there to match the power from the headunit to get a clean signal it will make it louder by turning it up but only at lower volumes so when u turn the headunit up with the gains all the way up on the amp your just going to make the coils in your woofer hott. hope that helps

RE: Setting your Amplifiers Gain with DMM
 

The purpose of the gain is to match the signal volts RMS coming from the source (CD player, etc.) to the input of the amp for correct power matching and to reduce clipping.

Here is a guide that will help you set the gain correctly http://www.box.net/shared/uchv4dbk88

You'll need a multi-meter (AC voltmeter, $15 from Radio$hack), Microsoft Excel and a way to burn an audio CD from an MP3.

If you don't have Excel, use this link http://www.box.net/shared/nkkw1dhk4g

See my site for more info http://spkrbox1.spaces.live.com

RE: Setting your Amplifiers Gain with DMM
 

why do you need Microsoft Excel??

RE: Setting your Amplifiers Gain with DMM
 

You don't need Excel but it sure is darned handy. The guide I made is an Excel spreadsheet that has a fully interactive power wire size calculator, alternator size calculator and "big 3" wire size suggestion section (for high powered systems) and a guide to set the gain on an amplifier correctly (0dB 60Hz test tone included).

I also have a link for those that don't have Excel, but it's just screen shots of an older version of the spreadsheet and is NOT interactive, however the test tone is still included.

If you don't have Excel, I highly recommend going to OpenOffice.org for a free Excel-like application program (and other MS Office programs like Word)made by Sun Microsystems (Java).

where can i get a test tone cd? can i download it from limewire?

Just thought I'd drop my 2 cents on here. Since we have setting up with a DMM covered, easiest method since most don't have an o-scope handy. One thing that was left out is that the DMM does NOT provide the resistance needed to the amp. So X-rms @ 2-ohms is out the window since you don't have the 2 ohm load. Neither does an o-scope.

My advice is a cheap set of ear protection and an open area away from your home. That way you can leave the actual speakers that will be on the system hooked up and give the resistance needed. It also helps so the wrong people don't learn what car in the neighborhood has a new system ;) Also, if you like to run your system at full-tilt most days... I suggest that you go over your system with a DMM every couple months. Set it to measure Ohms and check your speakers. This can let you know if you're cooking your coils.

For some awsome bass tracks and info, I recommend:
www.realmofexcursion.com
You have to sign up to access the downloads section (free), although I learned a lot from this site over the years. Anyway, go to the Downloads section and you can download Pink, White, Brown Noise in different dB levels, different freq. sine waves and even a few popular bass tracks like Bass I Love You.

Some of the members there are very well known in the Car Audio world.
Also:
www.the12volt.com
Those are 2 sites I highly recommend. Doesn't matter if you're an Audiophile hell bent on making your truck sound like a concert hall... or an earth-shaking Basshead. The more info you have, the better you can get your system set up and save you from making costly mistakes.

Awsome info btw Hillbilly... hope you don't mind me posting up more info. Oh and one last site I STRONGLY recommend if you're like me and love doing all your own stereo and alarms (or friends cars)...
http://techservices.audiovox.com
Sign up is free and gives you access to wire diagrams for almost any car/truck... well as far as stereos and alarms go lol. Whew, ok I think I'm done. WAY too much coffee and time on my hands this morning!
:icon_speaker1::icon_attention::icon_speaker1:

SMD Distortion Detector DD-1 - SMD Distortion Detector

Steve Meade's distortion detector is an incredibly easy way to set your gain to get the most out of your system with no distortion.
YouTube - ‪Proper SMD DD1 Testing for Head Unit and Amplifier-Installing New Amp with NO Distortion!‬‏