Having 40 plus years experience in the electronic industry. I started my very first project building an AC-DC tube AM radio. Those in my age group will know what this AC-DC tube radio is. I’ve had my share in the pro musical equipment arena. Repair, redesign, rebuild. From rewinding my own transformer, to modifying equipment. I had the privilege of having all kinds of tubes to use. RCA, GE, Raytheon, Toshiba, National, Philips, Telefunken, Mullard, and others. These were real good quality tubes. Coupled with excellent transformers using high quality cores, it was a time in which quality was tops.