Posted by Damir [ 213.202.114.199 ] on May 30, 2006 at 08:16:05:
In Reply to: A few measurements posted by 2wo on May 29, 2006 at 20:40:40:
Huh, something is missing - where did you exactly measured about 200Vpp? It is 100Vp or 70,7Vrms... Is this driver output? Or on (unknown?!) 300B load? This, 70Vrms "across" 16 Ohms means 70^2/16 = 306W... 
Thanks for the measurements, but please check this and report us again...
Converting in dB or vice-vers is simple. This is just the ratio of two AC signals, expressed in dB, log. scale.
If we have, say 1Vrms input, and output is 0,707Vrms (attenuation), then we can express this in dB like that:
A = 20 * log(V1/V2)
First, compute (on calculator) V1/V2 = 1/0,707 = 1,4142
Second, press "log" (from 1,4142), and this is 0,15
Third - multiply this (0,15) with 20 and you`ll get 3dB.
Note that the result would be the same (3dB) if we`ve had amplification, from 0,707 to 1V rms. It is the ratio.
Converting from dB to the amplification ratio, backwards:
-we have, say 3dB amplification, or A = 20 * log V1/V2 = 3 dB
-from that, log V1/V2 = 3/20 or log V1/V2 = 0,15
-on calculator, press INV log (of 0,15) and you`ll get 1,41 times
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