Do you mean 200W pk Class A. The amp I described is a 100W class A (200W pk class A)
XA.5 is push-pull again, so 50%
(an XA200.5 only does a handfull of single-ended Watts)
Patricia Barber ........
ahahaha...don't get that!!!
Anyway....what a bummer...so I drove 2hours to go to the green mill in chicago because I wanted to see Patricia before she would leave for her tour...so I get there and I see a different essemble testing the instruments on the stage.
So I checked their website and saw that patricia had just cancelled few hours before for unknown reason....grrrrr.....I had brought with me my vinyl connection to have her sign it.....ahahahahah....what a bummer!!
I will go see her then in October when she is back from her tour.
Anyhow....the other band was pretty good...the essemble was: drum, double bass, piano, voice and flute, saxophone and trumpet alternated by this one player.
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XA.5 is push-pull again, so 50%
(an XA200.5 only does a handfull of single-ended Watts)
I thought that XA would use more SE thus using Active device to achieve that.
I mean the difference with X.5 is only on the BIAS? I would think there would be more..
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I knew I had read it somewhere.
Quoting from Penaut Butter and Choccolate 's article by NP:
"The XA amplifiers operate at approximately 33% efficiency, that is to say they idle at three times their rated output. The XA200 is rated at 200 watts output into 8 ohms and draws 600 watts of AC power. This design is an exercise in highly conservative engineering, which provides exceptional reliability and product longevity. The 32 power Mosfet output devices are each rated at 125 watts and yet we operate them at a maximum dissipation of 18 watts. Each of these output devices operates at approximately 2 amps, well below the manufacturers rating of 14 amps; while exposed to no more than 70 volts instead of the 250 volts they are designed to endure"
This is referring to the first XA gen not the XA.5 and had TO3 devices isntead of the plastic version, but still the concept applies, the 2A Bias /each device
Quoting from Penaut Butter and Choccolate 's article by NP:
"The XA amplifiers operate at approximately 33% efficiency, that is to say they idle at three times their rated output. The XA200 is rated at 200 watts output into 8 ohms and draws 600 watts of AC power. This design is an exercise in highly conservative engineering, which provides exceptional reliability and product longevity. The 32 power Mosfet output devices are each rated at 125 watts and yet we operate them at a maximum dissipation of 18 watts. Each of these output devices operates at approximately 2 amps, well below the manufacturers rating of 14 amps; while exposed to no more than 70 volts instead of the 250 volts they are designed to endure"
This is referring to the first XA gen not the XA.5 and had TO3 devices isntead of the plastic version, but still the concept applies, the 2A Bias /each device
Measure exactly your absolute maximum peak voltage swing when playing at loud enjoyable levels then measure your speaker phase and impedance and consider building a SE amp based around your requirements.
I would go with voltage required then add another 10V, and bias it for your minimum impedance not 8 ohms. Then build
I would go with voltage required then add another 10V, and bias it for your minimum impedance not 8 ohms. Then build
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Remember our talks about your AX build on Graeme's (gl) AX100 Aleph-X thread ?
Read what Papa says there, April/May 2007.
NP likes it simple, why go active if arrays of 3W Panasonics between output and negative rail suffice ?
Papa mentioned more than once that the SE level is only a few watts, in the order of 5W.
Example pic of the XA30.5 (0R47 source resistor for each of the 240/9240, and a dozen 3R3 for the SE bias, in groups of 2 between the source resistors) => http://www.hifishock.org/galleries/Pass-Labs/Power-Amplifiers/XA30.5---1B.jpg
FaAB (the Fearless and Absolutely Bonkers)
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600W divided 32 makes 18.75W
70V max voltage means 35V rails (for balanced output, also needed for 200W/8).
18.75 divided 35 makes ~1/2A quiescent per device.
(aka 200W SE class A with static bias would bump dissipation level up to +1KW per channel. Tada !)
(XA200.5 not 32, but 80 outputs)
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This is exactly my point. Each device is NOT biased at 2A, but closer to 0.5A as said previously
How would you get to 1KW dissipation for a 200W SE?.
If efficiency is 33% it means that 200W SE equals 600W idle dissipation.
I would wonder however when there are more than 200W peak, how does the stage behave? While XA would just go in Class AB, would the SE stage would in class AB or would it gp into current clipping?
I get your calculation and I don't see how you can bias the device at 2A yet keeping dissipation under 20W, so you think that on the passage I quoted from Nelson's paper that 2A is a typo?
Maybe, just maybe was Nelson saying that at it's minimum rated load (2 ohms?, 1 ohm?, 1/2 ohm?
ahahaha...I don't think so. Nelson said that Bias for each device is around 2A
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