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Discussion Starter · #1 · (Edited)
Hi all. I'm following this guide to set my gains with a multimeter:

I'm setting 2 amps. Below is what I think I should be doing, but I would like help confirming.


Sub Amp (model noted):

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Per the instructions, I think I should be doing:
  • 1200 watts @ 1 ohm (at the amp)
  • 1200 x 1 = 1200
  • Square Root of 1200 = Set gain for 36.64 Volts
  • To get that, put (+) and (-) of multimeter as shown above: (+) on (+) terminal of left channel, (-) on (-) terminal of right channel.
  • Is this correct?

Mid/High Amp (model noted):
Product Human body Font Rectangle Parallel

Per the instructions, because the amp has 2 gain knobs, I'm a little lost. Is this correct?:
  • 100 watts @ 4 ohms per channel (treated like 2 separate amps due to 2 separate gain knobs)
  • 100 x 4 = 400
  • Square root of 400 = Set the 2 gain knobs for 20 Volts each
  • Do I put the (+) and (-) of the multimeter into the same (+) and (-) pair on one of the amp channels?
    • Ex: for the left channel in the picture, I would put them into that farthest left (+) and the (-) right next to it?
    • Then repeat for the right channel?


Hope I've explained this clearly.
Really appreciate any help with this.
 

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Discussion Starter · #3 ·
Are you sure it's 2 ohm per channel going to the mid/high amp? You can use your multimeter to check that. If it's 4 ohm that will throw your math off.
Well, no, its 100 x 4 ohm.

But in the example at the link I gave, it seemed like they switched it to 2?

Maybe I'm interpreting it wrong?

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I think that was just an example.

Your Pioneer amp has "Channel A" and "Channel B", each are actually 2 channels of output. They give you 2 gains in case you are using 2 of those for mid/high and the other 2 for say a sub, it allows you set the gain for each as you wish. in that case you may want to your sub to have more power than your mid/highs, so you would turn the gain on their side down.

so yes, your formula is correct, but figure 4 ohms on the pioneer amp, or whatever it is that is actually being connected to it (just round it to 4 or 2, no need to set them based on 3.8ohm or whatever it is.
 

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Discussion Starter · #5 ·
I think that was just an example.

Your Pioneer amp has "Channel A" and "Channel B", each are actually 2 channels of output. They give you 2 gains in case you are using 2 of those for mid/high and the other 2 for say a sub, it allows you set the gain for each as you wish. in that case you may want to your sub to have more power than your mid/highs, so you would turn the gain on their side down.

so yes, your formula is correct, but figure 4 ohms on the pioneer amp, or whatever it is that is actually being connected to it (just round it to 4 or 2, no need to set them based on 3.8ohm or whatever it is.
Thanks. Corrected the first post to 400 watts, 20 volts of gain.

What about the multimeter terminals on the 4 channel amp?

I assume I should apply them to a (+) and (-) right next to each other on that same channel when setting the gain. Correct?
 

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Things look good for you sub calculations.
However, on the four channel amp, since you have two gains, each gain controls 200w at 4ohms, so, you would set each gain half of the total output (100w) per channel, using the square root of (100watts x 4ohms) = 20v
When you measure the voltage, you are correct that you would place the leads on the (+) & (-) next to each other for each channel.

The important things to remember are:
  • Unplug the speaker wires from the amp
  • Set your head unit at 75% of its max output
  • Play a 50Hz tone when setting your sub amp and 1kHz on your 4 channel amp.
 

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Discussion Starter · #7 ·
Things look good for you sub calculations.
However, on the four channel amp, since you have two gains, each gain controls 200w at 4ohms, so, you would set each gain half of the total output (100w) per channel, using the square root of (100watts x 4ohms) = 20v
When you measure the voltage, you are correct that you would place the leads on the (+) & (-) next to each other for each channel.

The important things to remember are:
  • Unplug the speaker wires from the amp
  • Set your head unit at 75% of its max output
  • Play a 50Hz tone when setting your sub amp and 1kHz on your 4 channel amp.
Awesome. Thanks. I just updated the mid/hi amp to calculate as you mention.

Appreciate the help!
 

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Discussion Starter · #8 ·
So I'm trying to do this now via an app on my phone + Bluetooth connection to the head unit.

However, my voltage fluctuates at the amp based on my Bluetooth volume on the phone. Seems obvious, but what is my starting point for setting voltage?



2nd question - which of these 2 ACV settings should I be using on my multimeter? (pic below)
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If you have USB connectivity, you can download 50 and 1000 Hz tones here, it may be more stable that your bluetooth:

 

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Discussion Starter · #10 ·
If you have USB connectivity, you can download 50 and 1000 Hz tones here, it may be more stable that your bluetooth:

Thanks. This solved it entirely.

I went with the 0 db tones. I'm definitely not an an audiophile, but, the warning about "occasional clipping" on the -5 kind of spooked me. Should it?
 

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the "occasional clipping" is so you can get the most power out of your amp, but it won't be the cleanest signal to your speakers. Some distortion isn't audible in your subs, but too much will cause overheating.
 

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Regarding the question about the correct setting on you multimeter, the setting you have it on is correct, 200volts. For measurements of volts, ohms, etc... I try to use the closest setting above the expected output... for example on the DC scale, if you were expecting 14volts, use the 50volt scale because it allows for more accurate ranging in the readout.
 

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Discussion Starter · #13 ·
Regarding the question about the correct setting on you multimeter, the setting you have it on is correct, 200volts. For measurements of volts, ohms, etc... I try to use the closest setting above the expected output... for example on the DC scale, if you were expecting 14volts, use the 50volt scale because it allows for more accurate ranging in the readout.
Thanks. Great explanation.

Seems like its obvious to everyone but me. I always worry about which damn setting to use every single time I use a multimeter.
 
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