I am considering converting my 100W Jubilee 2555 clone to a 15W to 30W power supply. The smaller power transformer does not provide much for heater current though. I will probably end up running two 6V6 in it to start, but I want to still have the heater current to pop in either a pair of EL34 or 6L6 for tonal changes. My power supply might be good for 30W if I go to the big bottle tubes if I find I need a bit more power for special occasions. The power transformer I have only offers 3A on its 6.3V heater tap. But it has an additional 6.3V tap at 2A that I can also use. I am running four 12AX7 including the phase inverter. So I can use the 2A tap and run the 12AX7's off that, then run the power tubes off the 3A tap. Or move the phase inverter tube over to share the tap with the power tubes so preamp and power amp are isolated. Question here would be: Is there any noise or hum issues running two separate heater supplies? I might even try DC heaters for the preamp or could elevate the reference to ground as well if that could help?