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In Reply to: RE: voltage transformer for ss class A posted by Caucasian Blackplate on September 27, 2015 at 19:10:47:
there was a link on that page i posted where someone had tested the class a wattage...not sure what to make of it:
"I wonder about the class A power from the 30kg beast. Now that we have the schematics with component values, we can easily calculate how much power the amp really outputs in pure class A (and B if we want). Here are my findings.
PclassA = Irms x Irms x Rload.
There are two amps per channel in a bridged configuration, ie in total 4 amps - or amplifier stages if you like. Each of these stages has an idle current of (80mV to 100mV) / 0.25 Ohms x 2, as there are two pairs of output transistors per amp stage. Let´s use 100mV. Idle current aka
Ibias = 0.4x2=0.8A. This is the maximum current that a sine wave can have on the positive side. The negative side of course also can swing this much as we use a push pull design. So, Irms = 2 x Ibias / sqrt(2) = 1.13Arms.
Now we are ready to calculate the class A power that each of these four stages could deliver into a loudspeaker (Rload) :
P classA 8 Ohms = (1.13)^2 x 8 = 10.2 W
P classA 4 Ohms = (1.13)^2 x 4 = 5.1 W
P classA 2 Ohms = (1.13)^2 x 2 = 2.6 W
P classA 1 Ohms = (1.13)^2 x 1 = 1.3 W
Now, we do have two of these amps per channel in a bridged configuration. What does this mean for the class A power? Well, in bridged configuration, we have twice the voltage swing, so we get 4X the power, right? Yes, and no! We do get more class B power but do we really get more class A power? No, we do not.
Also note that in bridged mode, each amp "sees" half the Rload.
The power dissipation without music playing is high and that not only depends on the relatively high Irms but also because we have 4 amps."
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Follow Ups
- RE: voltage transformer for ss class A - m0reilly 20:00:05 09/27/15 (3)
- RE: voltage transformer for ss class A - Caucasian Blackplate 09:59:03 09/28/15 (2)
- RE: voltage transformer for ss class A - m0reilly 13:46:17 09/28/15 (0)
- RE: voltage transformer for ss class A - m0reilly 11:08:08 09/28/15 (0)
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