HellooooThar
100+ Head-Fier
Well that escalated quickly...
The manual with the 6n1p is not a production manual.
Running higher current tubes will likely have more impact to the amp's performance than just overloading the heater circuit.
Go ahead if you don't care about the amp, but don't recommend them to others.
Hm I never thought about it this way, but I bet you WOULD see an increase in distortion. I only say this given my experience overclocking computers. Asking for more power from inadequate voltage regulation circuitry (what the heater circuit is) will do one of two things in the short term: 1. blow it up. 2. lead to instability. Instability = voltage ripple or undercurrent. I can't imagine the DC power supply in the Lyr works much different!