I received my A50 2 days ago and started playing with it. Here are my initial impressions and progressive improvements (I have not started on the Skunkie modifications yet). The initial sound of the amplifier was very "thin" and not at all dynamic. I replaced the rectifier with a 5AR4 and heard a significant improvement overall. I then switched out the 6SN7s for USA Sylvania and the 300B for a Sophia mesh plate. Each of these swaps resulted in a much cleaner, crisper, dynamic and fuller sound. Overall I would say it made a 300% improvement to the sound to my ears at least. I did no THD testing yet as I was more interested in the sound and did not want to be swayed by numbers.

I will do the Skunkie recommended mods one at a time and listen to the results. Once I am satisfied with the amps I will run thru a full series of performance tests and publish the results on this forum. Prior to this, the other thing I will be looking at is converting the tube supply to a solid-state design. I know this will raise many eyebrows and I do not wish to get into an extensive debate about the virtues of one vs the other. I will share how I feel about the sonic difference. There are at least four highly regarded amplifiers, the McIntosh 240 and 275 as well as the Marantz Model 8B and 9, all use solid-state rectification. I have not read any suggestions regarding converting them to tube rectification.

Joe in Virginia