Morgan Jones book ordered
Does 'direct heated' just mean that the heater voltage to the valves is AC?
Directly heated means that the heater is also the cathode. It can work with AC in some cases.
Indirectly heated means the Cathode and Heater are not the same element.
Ian
Half of 6AS7 works very good with 2,5 kohm in my SE with cool bass. The same I can tell for PSE - Decreasing the output power with small Ri compensate mode PSE. This OT is small for EL34 in triod/penthod mode, IMO, sound will be sharp with small bass. Your output tubes must have Ri about 500 ohms,IMO. I doubt about KT88, 100. Maybe try KT120-150 with output power 8-10- 15 Wts per channel, OT has big iron, I like it.
Put me in the minority, but I like single-ended pentodes... provided the screens are regulated and there is some loop feedback. My current amp is a fixed bias SE EL34 with gas tube regulation and a 5687 driver. It's a great sound until the amp clips - so sensitive speakers are the best for it.
PT and OTs are very suitable also for 2A3, 300B, 6S4S /6BG4/ with cool and amazing sound, for a level higher EL34. Ra OTs - 2.5 kohm is small for EL34, be sure....If You want use only EL34, You can connect 5-8 ohm/5 Wt resistor in series to Your speakers to "lift" Ra OTs to 3-4 kohms, but output power wil decrease about 20-30 %. Sound will be suitable for hearing.
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