[InternetSandman]

Shopping around online and looking at different amps, some products list their power specifications as volts, or voltage rms, while others list it in watts. I haven't been able to find any resources online to help me compare the two, outside of the headphone power calculator on Headphonesty. This is mostly just scientific curiosity for the time being.

I have an Audioquest dragonfly red, which lists its output as 2.1 volts, and I've recently ordered a Schiit Hel, which lists its power output in a range of wattages into various resistance levels (1200mw into 32 ohms)

I know that wattage is a product of voltage and current, but I don't see specs for amperage alongside products that list power output in volts, so I'm not sure how to compare the two figures

 

[megabigeye]

Power is voltage times current: P=V*I
Current is voltage divided by impedance: I=V/R
Therefore, power is voltage multiplied by voltage divided by impedance: P=V²/R

These equations (known as Ohm's Law) use watts (W) for power, volts (V) for voltage, amperes (A) (aka, amps) for current, and ohms (Ω) for resistance. Headphone measurements are generally in milliwatts (mW) and need to be divided by 1000 for the equations.

Using this you can more or less extrapolate how much power, voltage, or current an amp produces into a given impedance.

Into the same 32Ω load as the Hel, the Dragonfly Red will produce:
P = 2.1V²/32Ω
P = 0.138W = 138mW

Voltage for the Hel:
1.200W = V²/32Ω
V = √(1.2W*32Ω)
V = 6.2V

 

[silent-circuit]

In my experience, if an amp only gives output in terms of volts, that's a weak amp. I'm sure there are exceptions, but this tends to be the case.