Question Regarding Setting Gain with DMM
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Tourer
Joined: Sep 2011
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From: Alabama
Question Regarding Setting Gain with DMM
From the sticky on setting gain:
Procedure:
1) What you now need to figure out is the V in the above equation. We know the P and R from the specs above. So, P = RMS output of amp at required ohms and R = ohms the amplifier will see from speaker(s) on that specific channel. In this example P=520/2 (260) (Im running a 2.7 ohm load to each channel) and R=2.7. So P(260) x R(2.7) = 702. Now you need the square root of 702 which equals 26.49 so V=26.49. This is the AC voltage that you will achieve by adjusting your gain(s) on your amp.
Question:
In this example wouldn't it be P=130W, Impedance = 2.7 ohms so V would = sqrt of 2.7*130 = 18.73? The reason I say this is that the load = 2.7 Ohms per speaker and there is one speaker per channel and the power per channel (speaker) is not 260W it is 130W.
Procedure:
1) What you now need to figure out is the V in the above equation. We know the P and R from the specs above. So, P = RMS output of amp at required ohms and R = ohms the amplifier will see from speaker(s) on that specific channel. In this example P=520/2 (260) (Im running a 2.7 ohm load to each channel) and R=2.7. So P(260) x R(2.7) = 702. Now you need the square root of 702 which equals 26.49 so V=26.49. This is the AC voltage that you will achieve by adjusting your gain(s) on your amp.
Question:
In this example wouldn't it be P=130W, Impedance = 2.7 ohms so V would = sqrt of 2.7*130 = 18.73? The reason I say this is that the load = 2.7 Ohms per speaker and there is one speaker per channel and the power per channel (speaker) is not 260W it is 130W.
Extreme HDF Member
Joined: Nov 2007
Posts: 14,670
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From: East of the Sun, West of the Moon
you're not setting gains on individual channels, you're setting them based on whether it's a 2 channel (being 1 amp) or 4 channel (being 2 separate amps).
I've not seen but a handful of amps over the years that allow individual channel gain adjustments
I've not seen but a handful of amps over the years that allow individual channel gain adjustments
Thread Starter
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Tourer
Joined: Sep 2011
Posts: 287
Likes: 4
From: Alabama
I agree you are setting gain for two channels by using the power output rating of two channels but using the impedance of only one of the two speakers connected to those two channels. That seems to be what I am stumbling on. It seems you would use power output and impedance values based on either one channel 130 / 2.7 or both channels 260 / ?, not power of two channels and impedance of one.
Extreme HDF Member
Joined: Nov 2007
Posts: 14,670
Likes: 139
From: East of the Sun, West of the Moon
because your amp sees a 2.7 ohm load.. not a 1.35 or a 5.4. The load is the same across the 2 channels. The only way this would differ is if you're putting a 2 ohm load on your left channel and a different ohm load on right channel. In that case, I won't be able to help you. 
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