^ They must follow the Mike Elliot (counterpoint) school of design. In the preamp I had, he used an EZ81 / 6CA4 rectifier with a CRC filter of 100uf / 500 ohms / 100uf. Datasheet for that rectifier has 50uf max after the tube, and I'm sure it likely performs better with something more like 20uf. When he was doing "upgrades" he was selling EZ80 / 6V4s and claimed they sounded "amazing" in place of the EZ81, Coupled with poor layout of the heater supply (ripple special). Lots of similarities.