PASS LABS X250 Question

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.

Hello Al,

I meant +/-100 volts... I took this number from Spectron web site:

"...in reality an amplifier's voltage headroom is limited by the power supply voltage, which limits the peak voltage. Spectron's amplifiers are the highest voltage we know of in the audiophile world, using a plus and minus supply of 120V. By comparison most amplifiers use power supply voltages on the order of plus and minus 85V or even lower. An engineer evaluating an amplifier to determine the required headroom would look at the output voltage of the amplifier with an oscilloscope while playing the loudest music he would reasonably anticipate would be listened to. At Spectron we have done that. What we see is that it is common in high quality recordings to see voltages near 100V peak, with medium efficiency speakers. This means that when listening to the same music with most other amplifiers, the signal would be 'clipped'... "

What we see is that it is common in high quality recordings to see voltages near 100V peak, with medium efficiency speakers. This means that when listening to the same music with most other amplifiers, the signal would be 'clipped'... "

Hi Mike,

I wouldn't take that statement too seriously. If it were true, most people would be experiencing intolerable clipping much of the time.

100V peak (200V peak-to-peak) is 625 watts rms into 8 ohms, or 1250 watts rms into 4 ohms. That would blow up many home speakers even if applied very briefly. And, using 90db/1W/1m 8 ohm non-planar speakers as an example of "medium efficiency speakers," 625 watts would correspond to a sound pressure level of around 112db at a listening distance of 10 feet.

Accurately reproducing the cannon shots on Telarc's notorious recording of the "1812 Overture" might require that, but I would expect that not much else will.

Best regards,
-- Al