Amp Gains w /MultiMeter

[TheChicksDigIt]

To try to be as close as I can, I recently set my amp gains with a voltmeter. I have 1 Skar 800.1 set "correctly" and 1 Skar 500.4 going to 4 6.5's. When setting the amp gain for the four channel, my target voltage is 17.34 however I have the gain turned all the way up and maxed out at 16.59 volts. If this reading is correct I know it is not a big deal, but I wanted to see if anyone has ever had an amp not reach their target voltage? The amp is rated at 75 Watts RMS at 4 OHMs while the speakers are rated to handle 80 Watts RMS at 4 OHMs. Thanks in advance!

[Dafaseles]

1 hour ago, TheChicksDigIt said:

To try to be as close as I can, I recently set my amp gains with a voltmeter. I have 1 Skar 800.1 set "correctly" and 1 Skar 500.4 going to 4 6.5's. When setting the amp gain for the four channel, my target voltage is 17.34 however I have the gain turned all the way up and maxed out at 16.59 volts. If this reading is correct I know it is not a big deal, but I wanted to see if anyone has ever had an amp not reach their target voltage? The amp is rated at 75 Watts RMS at 4 OHMs while the speakers are rated to handle 80 Watts RMS at 4 OHMs. Thanks in advance!

What head unit are you using? 

If the pre out voltage on the RCA's are too low, this can cause issues with gain setting with a multimeter

[TheChicksDigIt]

Kenwood KDC-BT378U with 3 2.5v outputs

[Dafaseles]

26 minutes ago, TheChicksDigIt said:

Kenwood KDC-BT378U with 3 2.5v outputs

2.5v is low. Preferably, you want 4-5v pre outs. 

Some options you have are getting a line driver, or an Audio Control Three.2. I have the Three.2, and I love it. It has a feature where it functions kind of like a line driver, and boosts the voltage from your RCA's, so your gains don't have to be turned up all the way

[TheChicksDigIt]

I might just return the headunit then..

[TheChicksDigIt]

if I turn up any of the loudness setting on the receiver, will that alter the voltage at the amp

[Dafaseles]

11 minutes ago, TheChicksDigIt said:

if I turn up any of the loudness setting on the receiver, will that alter the voltage at the amp

It will alter the voltage, but that doesn't mean you won't be sending distortion through the amplifier. The only way you can see that is with an oscilloscope (and even then it's not guaranteed you'll see it) or a DD-1+

[audiofanaticz]

2.5 volts is way more than needed to properly adjust the amplifier gain, period!

So you shouldn't need to add bass boost or loudness of any kind on the radio to reach the needed voltage.

 

An amplifiers gain adjustment has adjustment from 0.2 volts to 6 volts on average, as long as your headunits rca preout voltage falls between those two numbers you should be able to properly set your gain so that it is matched with your radios preout voltages.

 

So if your radio put out 6 volts on the preouts you would use no gain, if it put out 5 volts you would use a very little, if it put out only 0.2 volts your gain would be all the way up. 

So with 2.5volt preouts you should be a little under halfway up. That being said if your all the way up and not even coming close to the needed output wattage theres only a few things preventing this.

 

1- Your RCA cords are garbage and have so much resistance in them due to a poor connection on the plug, poor soldering inside the plug, really small gauge wire, or a combination of all that which is causing voltage drop from one end to the other. 

2- You have your crossovers set wrong which is limiting the output of the amp, or you set your crossovers before setting the gain.

3- Your amp is heavily over rated and doesn't make the power the manufacture states.

4- This goes along with #3 but this is why using a dmm to set gains is not always a great idea because if your amp is over rated and you have no clue you are pushing your amp into a hard clip in an attempt to reach the amps output voltage and you have no idea you're doing so. Now on the other hand if your amp is underrated and makes way more power than the manufacture says you are now setting the amp to produce much less power than it could do cleanly, so you're leaving a lot on the table that you paid for but had no clue.
5- This goes with number 4 on the dmm side of things, but a quality True RMS dmm should be used, cheaper dmm's are not as accurate. The test leads on your dmm could also be bad or going bad causing a bad connection and not allowing for true readings to be seen.

[MrSkippyJ]

What is your volume setting on the head unit when you set your gains? 

[meade916]

Don't use a dmm to set your gains.  That is a total waste of time. Might as well just guess your settings.  Same exact outcome.