QUOTE(AlamakLor @ Sep 7 2006, 01:15 PM)
V=IR
P=I^2 * R or P= V^2 / R
I^2=P/R
I^2=0.05/300
I=sqrt(0.05/300) = 0.013A (13mA)
Vrms=0.013*300=3.9
The THD is <=1% when the amp is driving a 300ohm phone (say a sennheiser) at 3.9Vrms.
I^2=P/R
I^2=0.092/300
I=sqrt(0.092/300) = 0.018A (18mA)
Vrms=0.018*300=5.4
The THD is <=3% when the amp is driving a 300ohm phone at 5.4Vrms.
How loud is 3.9Vrms or 5.4Vrms? take a test tone generator and play a 1khz freq @ 0db. Take your multimeter and take the measuremet at that volume then plug in ur headphone and give it a try.
let's say you are listening to a volume of 6Vrms with your 555, your headphone is sucking up:
V/R=I
6/50=0.12A (120mA)
P=0.12^2 * 50 =0.72W (720mW)
50mW, THD <=1%
92mW, THD <=3%
120mW, THD <=
if the amp is driving 50ohm senn,
it sucks up 31mA ( 3 times the 300ohm does )
and Vrms = 1.55 Vrms
so, the THD is <= 1% when the amp is driving a 50ohm at 1.55 Vrms?
in other words, the THD for driving 50 ohm phone is quite high although it's in low volume, right?
QUOTE(AlamakLor @ Sep 7 2006, 01:15 PM)
y u still like tubes le?