McAnally,

The distortion figures show that 3rd harmonic distortion is slightly more than 2nd harmonic distortion. Hence, is the sound a bit sharp and nasal at higher output levels?

djk, thanks for your input. After a lot of study, I have come to the conclusion that trying for power levels such as 500watts into 8 ohms is rather expensive and risky. My requirement is to drive 8 Nos. 18" EV woofers (horn loaded), either each with its own power amp (400 watts of the woofers + a bit of headroom for the amps) or to be able to drive 1kw bridged into 4 ohm or 1.6kw bridged into 2 ohms. This means four bass bins per side, all paralleled into one bridged amp or 2 each paralleled into 2 bridged amps.

Hence, can this design be operated at lower voltage and more output devices to drive typical low impedance loads as I have stated above.

djk, by the way the 2SD669/B649 devices are used by Randy Slone running at 85volt rails in his OPTIMOS 400 watt designs. Is this sailing too close to the wind? I ask, since this is another design I am considering - 8 mono amplifiers, one for each bass bin.

Thanks again for further inputs,