sKiZo
Hates received: 92644 43.20°N 85.50°W
As you've guessed, it's mostly the iron. Circuits and chassis are pretty much identical otherwise with some minor tweaks here and there to handle the higher voltages.
From Roy's website:
- The power transformer instead of 360-0-360 secondaries like the ST-70 has 420-0-420 secondaries and puts about 485 volts on the plates (pin 3) of the output tubes. The ST-70 puts about 420 volts on the plates. The stack lamination on this transformer is about 2.70 inches tall.
- My ST-70's power transformer stack is about 2.05 inches high. This transformer weighs about 4 pounds more than the ST-70 transformer and is rated at 425 milliamps of current flow.
- The output transformers have 4200 ohm primaries, 40% ultralinear screen taps and are 3 7/8" tall, 3 1/4" wide and 3 1/8" deep (about 1/2" taller, 3/8" wider and 1/4" deeper than a stock A-470 output transformer). Each output transformer weighs about 2 pounds more than a stock A-470 output transformer.
- The power storage caps have a higher capacity and voltage rating than the VTA ST-70.
From Roy's website:
- The power transformer instead of 360-0-360 secondaries like the ST-70 has 420-0-420 secondaries and puts about 485 volts on the plates (pin 3) of the output tubes. The ST-70 puts about 420 volts on the plates. The stack lamination on this transformer is about 2.70 inches tall.
- My ST-70's power transformer stack is about 2.05 inches high. This transformer weighs about 4 pounds more than the ST-70 transformer and is rated at 425 milliamps of current flow.
- The output transformers have 4200 ohm primaries, 40% ultralinear screen taps and are 3 7/8" tall, 3 1/4" wide and 3 1/8" deep (about 1/2" taller, 3/8" wider and 1/4" deeper than a stock A-470 output transformer). Each output transformer weighs about 2 pounds more than a stock A-470 output transformer.
- The power storage caps have a higher capacity and voltage rating than the VTA ST-70.