Setting Gain

[Blunt 10+ year member]

So i understand how to set the gain for the rated amp power but what about underrated amps? What about amps that aren't advertised at .5 ohm but will do it?

was thinking about a 20.1 or a 2500d but was looking at others too but didn't know how you would set the gain on any of them with a dmm

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[Blazin_Jason 10+ year member]

You use the resistance (ohm) load of the subs and what RMS you want them to run at, not the amp.

 

[Blunt 10+ year member]

no you dont cause if i have a 500w amp no matter if its 50w underrated or not if i set the gain for 551w and it cant do it im gonna clip it so you really need to know what the actual output is then correct? if so how do i find that out. if i have to buy new tools well then so be it i like new tools

 

[Blazin_Jason 10+ year member]

So you set your gain to the max rms output of your amp? Probably need an oscilloscope to check that.

 

[thch 10+ year member]

So you set your gain to the max rms output of your amp? Probably need an oscilloscope to check that.

or a good DMM and a lot of time and blissful ignorance of engineering basics.

for one you have to be sure you want the gain to be the same as the DMM method reccomends.

second you have to assume that the charging sysem never changes, ever. the speakers cannot signifigantly affect the amp (or test with the speakers in).

but if you ignore those, you can determine distortion based upon iteritive tests. a high pass crossover is a great tool because it will filter out the normal signal but pass distortion from clipping. as you turn up volume, you alternate between 2 settings on the HU. you know that this should give a 2dB increase*. if the AC voltage on the highpass filter output increases by more then 2dB then extra energy is in the system (highpass sytem i mean). or if the output before the highpass jumps by less then 2dB then some energy is not being output = clipping.

the highpass filter gives better resolution. i'm not sure either method is any better then the ear method. you probably can't distinguish THD less then 5% with this method. at least without building custom hardware (a bandstop filter to completely cut out 60hz, so that only distortion is measured)**

*example only, actual HU could also have 1dB or 3dB steps.

** among other things.