What's the difference between amplifier gain and watts?

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[robertbrown]

I'm no expert, but it seems this would have benefited greatly with the inclusion of a brief overview of Ohm's Law (fittingly). Two excerpts of this can be used to flesh out the illustrations of "40 volts into 8 ohms is 200 watts, " and "40 volts into 4 ohms is 400 watts."

Two excerpts from Ohm's Law:
1. Volts = Amps x Resistance (V=IR) [for those unfamiliar, amps/amperes is the unit for electric current, often represented by an "I" in equations, and ohms is the unit for electrical resistance]
2. Power = Amps x Volts (W=IV) [for those unfamiliar, watts is the unit for power, electrical in this scenario]

Plug in the relevant units from the first illustration into the first, then second equations above:
1. 40 = I x 8, solve for I:
I = 5 amps... then,
2. W = 5 x 40, solve for W:
W = 200 watts

Plug in the relevant units from the second illustration into the first, then second equations above:
1. 40 = I x 4, solve for I:
I = 10 amps... then,
2. W = 10 x 40, solve for W:
W = 400 watts

As Paul mentioned, Gain is just a term for a simple multiplier applied to the voltage prior to plugging numbers into the equations above. As voltage is increased, the amount of current (amps) needed will increase.

The severity of increase in current (amps) will depend on the load (resistance, ohms) of the speakers; bear in mind that the resistance is a fixed value determined by the speaker's construction, and as such it is the only constant in these equations.

With both the voltage and current (amps) increasing, the power (watts) consumed by the system increases also. If your gain setting calls for more current than your amplifier can provide, you'll get clipping. And if your amplifier pulls more power than your breaker can handle, it'll trip. Let's hope for neither!

[rakeshmahindrakar]

Paul said it clearly, if you did not understand, please watch the video again.!!
Thank you Paul for the effort you put in making these videos.!!

[dnp_x]

Bottom line: Never ask that question again!

[jeremiahchamberlin]

Paul has really helped me understand something —the relationship between gain, ‘volume, ’ and power— I thought I knew (kinda). 🙂 Thanks, Paul.

[doylewayne]

oh boy...the gain of understanding is clipping my mind...thanks Paul

[carstenjunge]

Thank you; Takes me back to my engineering classes at the

[paulrs]

Most systems have too much gain. One thing I keep hearing over and over: "my system plays loudly even with the volume only 1/4 way up. It therefore has a lot of power". Not correct! And this could be a bad thing for sound quality.

[mikebest]

I actually understood that, and it makes sense! Thanks Paul!

[homeboi]

2.83 volts = 1W into 8ohm
(2.83)^2 / 8 = ~1

If the amp gains takes in 2.83V and gains it by 20dB, that’s 100W (10x to gain +10dB, so 100x to gain +20dB).

However, amps don’t need 2.83V, they are able to output max power with usually 1.3V to 2.0V.

If 2.0V input, with no gain that’s 0.5W into 8ohm (2^2 / 8 = 0.5), and would need a gain of:
3dB to be 1W
6dB to be 2W
9dB to be 4W
12dB to be 8W
15dB to be 16W
18dB to be 32W
21dB to be 64W
24dB to be 128W
etc.

So yes, 20dB to 30dB of gain is typical. If an amp doesn’t need as much input voltage, that means it’s internal gain must be higher to compensate.

[srdjan]

Perfect explanation 😃 Paul is the teacher i had 😃😃

[ThinkingBetter]

Amplifier gain is the ratio of output voltage vs input voltage. Wattage of an amplifier is the energy per time available on the output side to move your speaker cones. One Watt is one Joule per second. A 100 Watt amplifier is producing 100 Joules per second. Not actually much. The energy of a single BigMac is 2, 250, 000 Joules or your 100 Watt speaker power for 2, 250, 000/100 = 22, 500 seconds or approx 6 hours of playing music at maximum! In other words, a 600 Watt amplifier produces as much power as that of eating a BigMac per hour 🤔

[TheFilletingfish]

Thought subject to master in 5 min. Well done Paul for trying.

[moukiebengal]

sorry, didn't understand one bit of what you said !!

[Taronlusin]

Before I did't understand, now I am totally confused.

[louisperlman]

Hi Paul, what happened to good old V=IR, P=I(2)R and P=VI? I learned this back in high school, and it obviously stuck.

[spacemissing]

No matter how well it's explained, this subject just doesn't make sense to some people.
Those of us who Do comprehend it will never understand why others can't.

[ducky]

"The Gain Remains the Same."

Any excuse to listen to Led Zeppelin.

[surkhablife]

This gain is what I’ve always struggled with as I have to set these in my car. I’ve seen your earlier videos on it too and this was the best so far. Here is a funny question. If my active setup in car running on a very good 4 channel amp has a gain ‘A’ for my tweeters with 92db sensitivity and now I change to a new pair of tweeters having 96 dB sensitivity will my gain need to come down? Having everything else remain same. Hope to own a PS Audio amp one day. Thanks and regards.

[StephaneVorstellung]

I really can't follow it (or communicate it?) by measurement. My understanding comes through playing with guitar amplifiers and overdrive pedals (not distortion pedals, to be clear). Gain, volume, headroom are mutable concepts that are best understood by playing around with them. Go to a guitar store and mess around with a combo amp. Find one with gain (sometimes called overdrive), volume, and master volume. You will then see how these elements relate and behave (if you can find an amp with an attenuator, even better). You'll be no wiser in terms of measurements, but you'll understand it.

[robertsparkman]

Always hated db, it's unintuitive, for me at least. Basic stuff but so hard to describe simply. Good job Paul.