50 year old triode tubes single ended 3.5 WPC

This amp uses all triode tubes in single ended configuration and thus the circuit as short and sweet as possible. The result was 3.5 watts per channel, with 0.07% distortion at 1kHz, 1 watt and not much worse at the extremes. We also did not have the deep pockets to try the more exotic transformers and coupling capacitors available. I'd like to, though, and set up my A/B switch box to see if I could discern any difference. The A/B test with myself and others paired with a high end solid state amp with 0.007% distortion, or ten times less did not reveal any discernible difference. I have a notion that some high end speakers might make the biggest difference of all. The row of LED's are a clever circuit we designed which indicate 3 decibel increments of sound pressure level (SPL). Each 3 decibel increase in loudness requires a doubling of wattage, as many of you know. These light up in sequence , e.g. 0.04 watts, 0.08, 0.16, 0.30, 0.7, and so on to 8 watts total.