One cool trick, (though the topic is quite old). You can pick up pretty powerful transformer with decent powerful 6.3 heater voltage (quite more powerful than the total heater + plate current of your amp ). Connect the 6.3v out of that tranny to the heater 6.3 voltage connections of your tube...

Hi,great and cheap amplifer.I guess you're quite experinced.So let me ask you a question: What if I heat in such way a PCL86 (13.3v) and ecc83 (6,3)? Roughly I mean this: ____________           -------I I                                                 I...