These are very good amps.They retail for $1660 a pair,but use better parts and circuitry than most amps at twice the price.They have unregulated power supplies (no current limiting) and run in class A up to 40 watts output,and class AB1 above that.They come with GE6550 output tubes- two per amp- but they can also use KT88s,KT90s,and KT99s.They are rated at 75 watts per amp into 4,8 or 16 ohm loads.They use some of the biggest transformers of any amps in this power range,and are extremely wide bandwidth (16-80,000 hertz).They sound lush and detailed,but with plenty of sparkle in the highs and lots of authority and control in the bass. They were designed by Bruce Moore who also designed products for Audible Illusions. All in all very good amps.