Audio Power Labs
Audio Power Labs buys the 833 Richardson in Texas who imports them from China. Lots go through a matching process that yields 60 pairs, with the rest sold on eBay at cost.
The microprocessor-controlled amplifier has no capacitors in the signal path. It has less than 1% THD at rated output with a frequency response of 15Hz33kHz ±3dB. The company also sells the 50W 50TNT monoblock for $47,500/pair. It has a frequency response of 15Hz25Hz, ±3dB with less than 2% THD from its 8 ohm output tap. Unlike the 833TNT, its 572B output tubes are no longer manufactured, so Audio Power Labs has sourced over 700 tubes for their production and warranty work.