PASS LABS X250 Question

Michael, my calculation was based on the assumption that sensitivity is defined as the rms input voltage that is required to drive the amplifier to its maximum rated rms continous power output. I'm not 100% certain, but I believe that is the correct assumption.

If I understand your post correctly, you appear to be assuming that sensitivity is defined as the instantaneous input voltage required to drive the amp's output to its maximum possible instantaneous output power level (the peak of a sine wave). That assumption strikes me as unlikely to be true, given that amplifier power ratings (and speaker power-handling ratings) are as far as I am aware always specified on an rms basis.

Confusion sometimes arises due to loose usage of the term "peak." "Peak power" can refer to the power corresponding to the peak of a sinusoidal waveform, but it is also often used to refer to "MAXIMUM rms power."

Regards,
-- Al

Michael, my contention appears to be further supported by information in the manual for the .5 series amps.

Note that the X250.5 (for which the output current, voltage, and power ratings are almost identical to those of the X250) is indicated as having a gain of either 26 or 30 db, and sensitivity at 26 db gain is spec'd as 2.24 volts.

Therefore sensitivity at 30 db gain is presumably 4db less than 2.24 volts, which is almost exactly equal to the 1.4 volts I had calculated!

Regards,
-- Al

Hello Al,
I stand corrected.
Interesting that since 26 dB is equivalent to x20 then the rms voltage is 2.24 x 20 -45 volts and then as per your definitions, maximum output voltage [ = sqrt(2) x V(rms) ] = 65 volts.
If so this amp (200.5) would clip easily as signal from an amplifier into medium load speakers is about 100 volts and difficult loads much more then that (of course during the loud musical peaks)

Thank you
Mike

Hi Mike,

I suspect that the 100 volt figure you are thinking of is peak-to-peak, not peak. Note in the manual that the maximum output voltage spec of the X250 is indicated as "plus, minus 65 volts," the 65V therefore obviously being peak, rather than peak-to-peak.

100V peak-to-peak corresponds to about 156 watts rms into 8 ohms, or 312W rms into 4 ohms, and would be well within the X250's peak-to-peak voltage swing capability of 65 x 2 = 130 volts.

Based on that voltage swing capability, as you will realize it can readily be calculated that the amp will not clip until an output power level of 264W rms (or more) into 8 ohms is reached, or 528W rms (or more) into 4 ohms.

Best regards,
-- Al

Al, thanks again.