Harman Kardon Citation V Amplifier
This amplifier is the little brother to the Citation II listed above. Rather than use the complex and expensive driver topology of the Citation II, this amplifier uses a typical Mullard type driver topology. A pentode (12BY7) drives a dual triode (6CG7) set up as a long tail pair. This drives a pair of 6L6GC class output tubes operating in a fixed bias configuration.
This amplifier is much more simple than the citation II, but has what I'd consider a couple design flaws. First, I can't fault the basic signal path, like all the citation gear, that is solid top to bottom. However, this amplifier has controls for AC and DC balance adjustments, but no bias adjustment. Like the Citation II, this amp wants to run the output tubes hard. The AC and DC balance adjustments are great, every amp should have them. But the lack of a bias adjustment in this age when 7581's (the original power tube) are getting hard to find, is a bad thing. The stock bias runs a pair of standard 6L6GC tubes right at the ragged edge of max plate dissipation. So I added the ability to adjust the bias via a pair of 10K multi-turn pots on my capacitor board.
The capacitor board I've designed replaces the electrolytic caps in the main and bias power supplies as well as the resistors and diodes in these supplies. As always this capacitor board allows much larger value capacitors to be installed if desired.
When the passive components in this amp are updated, this amp sounds just very good. It produces music with about 90% of the qualities of the citation II but with a bit more sweetness. It tends to have a dry and "correct" sound rather than a "tube amp" sound much like the Citation II. This amplifier lies somewhere between the warmth of many tube amps like the Dyna ST-70, and the total correctness of the Citation II.