Different SUPPLY configurations:   Tube type Primary connections Secondary connections Typ. bias point Ideal supply KT66/807/PX25 P1+P2=230V@40Hz or P1//P2=115V@40Hz P3-4: NC or pre-amp S1-2: power tube heating (>6.3V/2.6/1.9/2.6A) S3-4: driver tube heating (>6.3V/1.2A) S5-6: NC S7-8: FW-supply (>2X430VDC/0.15A) 62.5mA@400V Pa=25W 438VDC KT88/6550/300B P1+P2=230V@40Hz or P1//P2=115V@40Hz P3-4: NC or pre-amp S1-2: power tube heating (>6.3V/3.2/3.2A) S3-4: driver tube heating (>6.3V/1.2A) S5-6: 300B heating: (>5V/2.4A) S7-8: FW-supply (<2X430VDC/0.22A) 100mA@400V Pa=40W 443/480VDC 6C33/1H One heater/tube   (P1+P2)//(P3+P4) =230V@40Hz or P1//P2//P3//P4 =115V@40Hz S1-2: power tube heating (<6.3V/6.6A) S3-4: driver tube heating (>6.3V/1.2A) S5-6: NC S7-8: FW-supply (<2X430VDC/0.32A) 150mA@300V Pa=45W 395VDC 6C33/2H One UNI/channel (P1+P2)//(P3+P4) =230V@40Hz or P1//P2//P3//P4 =115V@40Hz S1//2//3: power tube heating (<6.3V/13.2A) S3: driver tube heating (>6.3V/1.2A) S5-6: NC S7//8: FW-supply (<430VDC/0.42A) 200mA@300V Pa=60W 410VDC 845 One UNI/channel (P1+P2)//(P3+P4) =230V@40Hz or P1//P2//P3//P4 =115V@40Hz S1-2: NC S3-4: driver tube heating (>6.3V/1.2A) S5+6: power tube heating (<10V/6.4A) S7+8: FW-supply (>860VDC/0.17A) 75mA@840V Pa=65W 960VDC 845 Power enhanced One UNI/channel P1+P2=230V@40Hz or P1//P2=115V@40Hz P3+P4=added to S7+8 S1-2: NC S3-4: driver tube heating (>6.3V/1.2A) S5+6: power tube heating (<10V/6.4A) S7+8+P3+P4: FW-supply (>1100VDC/0.17A) 100mA@1kV Pa=100W 1100VDC
	Typical suggested Universal Transformer Supply usage. Heater and supply voltages are estimated only and the fact that heater voltages may vary within as much as +/-10% has been taken into consideration and noted. Driving circuit is always supposed to be swing-modified Williamson push-pull 6SN7 drive. Use of 6SL7 drive may have to be considered if input level or feedback is high.