Due to the still large heatsinks it appears to me they still use their old Class-A/B Mosfet architecture. And why not? It was a landmark in the '80-ties and '90-ties. And sound wise to me it can still cope with most of the top amps today! Here a pin-up of the 3370 I restored recently:
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It was modified almost to death by some Audio Magician. When It arrived at my desk very large 4,7 uF 1000V Mundorf Silver foil caps, that merely belong to an audiophile speaker x-over, were strapped to the back as input capacitors. Very good hum catchers I know now! Also the feedback loop was modified and the poor thing cried (oscillated) out loud. Luckily all mosfets survived! You can still see the burned PCB under the zobel resistors at the top left. And if you ever touched the smell of burned epoxy PCB... The thing went firstly 2 weeks in quarantine for it. Top right the Hypex soft start.
After fondly restoration, the thing is now happily in service again. Here how it performs at 300W into 8 ohms:
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Mains hum looks a bit misleading dramatic here but it is about -108dB and distortion quite low. It's an order lower than specified in the manual.