The old non-Citation H-K tube gear is wonderful. I have
rebuilt a number of the Award series integrated amps and
a Festival series or two as well.
The non-Citation Harman Kardon gear is very good when rebuilt. Easily up there with the Scotts, Fishers, and Sherwoods of the day. The A300 is one of the sweetest sounding little integrated amps you will ever hear. It is a 6V6 push pull amp that does about 14 watts/ch as memory serves. The A500 is easily converted to a 6L6 amp and it sounds fantastic. Both of these are greatly improved when a small toroid transformer is added internally to drive a regulated DC filament supply for the phono and line stage tubes. The cathode resistor for the output tubes is replaced and converted to two resistors and bypass caps, one for each channel. The amp is completely transformed by these simple mods. I have done three or four Citation IIIx tuners as well. These are great when working correctly! I have also done a number of Citation IV preamps. If you rebuild the power supply and make it full instead of half wave it is a great improvement. They also used electrolyitic caps in the signal path. These are most likely WAY out of spec after 50 years. If they are replaced with good quality modern parts during the rebuild it is a huge improvement! It is really a very good preamp with a nice phono section.