PASS LABS X250 Question

Pass amps are typically very unrated in power. My X150 amp puts out around 250 watts into 8 ohms and I think pushing 400 in 4 ohms. I don't doubt the X250 probably easily puts out 600-700 watts into 4ohms. I have never run out of steam with my X150 amp. This is on Eminent Tech speakers which are very inefficient. You should be fine. Plenty of head room with the X250 and I hear the X240 is the best sounding one of the bunch in that era prior to the .5 amps.

I agree that X250 can easy output 400 watts rms into the load of 4 Ohms.

I disagree with the calculation of the sensitivity. Almarg use relation between rms and peak in ....sinusoidal waveform which is not the case here.

I cannot calculate exactly but I would take as a reference peak output current of 65 volts which should be slightly below rail voltage (65-70 volts) and then devide it over 31.6 times so it would seem to me that its sensitivity is 2 volts (go get its peak power whatever it is). Balanced input , in theory should be double indeed or about 4 volts.

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