[LemanRuss9]

hi headfi
so how do you know an amplifier is strong enought to drive a headphone/iem?

 

[NA Blur]

It depends on your headphones.   You need to know the impedance as well as the sensitivity.  The sensitivity comes in two flavors.  The first is dB/mV and the other is dB/mW.  Typically a headphones is rated in dB/mW as this was the old standard for speakers.
 
We need you to list your headphones impedance and sensitivity.  If the sensitivity has units please include that.  Or you can do the calculations yourself.
 
In volts your amp is going to need:
 
Let's say your headphones are rated for 91dB/mW and have a 30 Ohm Impedance.
Power = 10^(Desired dB - db/mW of headphone )/10
=
Power = 10^(say 112dB - 91dB/mW)/10
=
Power = 125mW
 
For the voltage side of things:
 
V = I*R
P = V^2/R
P = 11mW ( from above )
11mW = V^2/R

R in our case is 30 Ohms

Remember that:
1 Watt or 30 dBm = 10*log(1/.001)
That is where the first 30 comes from below.

Take the log of both sides to find:

dBm - 30 = dBV - 10log(R)

dBm -30 = 91db/mV - 10log(30 Ohms )
dBm = 106dB/mV
 
So your headphones have both a 91dB/mW and 106dB/mV rating.
 
Your amp will need to be able to swing a voltage of at least:
Voltage (RMS ) = 10^(Desired dB - db/mW of headphone )/20
=
Voltage (RMS) = 10^(say 112dB - 106dB/mW)/20
=
Voltage (RMS) = 2.0 volts
or
2.82 volts Peak ( RMS / .707 )

 

[proton007]

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