Then stick with AC. This is a cutting edge design and not meant for a one time amp builder. Rod is pushing the envelope and I appreciate his approach.
It's not all or nothing. Different transistors can be used - with some loss of performance, depending on the devices. Even at something short of the optimum, it's a a good filament supply.
Sheldon
Gianluca, I think it will be possible, but some extra precautions are needed:
- the heatsinking must be very large, about 0.7K/W
- DC supply must be 10,0V +/- 1V
- I must make some small component changes.
I'll try it when I can.
Bigun, the transistors are important, but I have now identified 5 or more parts that meet the requirements. I list these out when the tests on them are done.
Also, I plan to buy large stocks of parts, and will sell transistors to any that may want extras for spare parts. I'll try to keep enough stock to satisfy any repair needs that may arise.
Thankyou, several of us plan on trying this heater will highl sensitive headphones so obviously don't want to trade performance for convenience.
OK, 845 (3.3A 10V) will be a standard kit, available soon.
For indirectly heated valves like the EL34 and 6SN7, there will be a standard kit to suit them -although the performance upgrade compared to ac heating is not as big as it is with the Directly Heated triodes & pentodes.
Right now, I'm working through the different kits, and evaluating the performance and power supply requirements for each design. Then, I'll finalise the parts lists and kit contents, and have the prices ready - very near now.
For indirectly heated valves like the EL34 and 6SN7, there will be a standard kit to suit them -although the performance upgrade compared to ac heating is not as big as it is with the Directly Heated triodes & pentodes.
Right now, I'm working through the different kits, and evaluating the performance and power supply requirements for each design. Then, I'll finalise the parts lists and kit contents, and have the prices ready - very near now.
Member
Joined 2009
Paid Member
Hi - on vacation for a few days, but some progress to report:
So far we have the 250mA, 250mA/#26 switchable, 300B, and 2A3 versions all characterised. They are working well - with sub mA ripple in 3A versions, even with 200mV input ripple voltage. Voltage headroom required is 4V minimum for sure, less typically. The GM70 version [20V 3A] has taken some time to get under control, due to the big switch-ON power pulse in the power transistors. (That's to say - the first versions failed due to overstress from the 24..25V-supply needed in these transmitting tube filaments). I wanted to have all the versions ready at once, as I believe many folks want the GM70 along with orders for the lower power heaters.
Meanwhile, the documentation in terms of assembly guides, power supply build examples, heatsinking worked examples is advanced but not complete. It's been quite an effort to prepare all these! Hoping to have a big finishing effort when I get back, and on with the release - I have plenty of PCBs stocked.
Apologies for the wait - I intend to offer a well-documented, well-supported offering, - thoroughly tested by the time it is released.
Rod
So far we have the 250mA, 250mA/#26 switchable, 300B, and 2A3 versions all characterised. They are working well - with sub mA ripple in 3A versions, even with 200mV input ripple voltage. Voltage headroom required is 4V minimum for sure, less typically. The GM70 version [20V 3A] has taken some time to get under control, due to the big switch-ON power pulse in the power transistors. (That's to say - the first versions failed due to overstress from the 24..25V-supply needed in these transmitting tube filaments). I wanted to have all the versions ready at once, as I believe many folks want the GM70 along with orders for the lower power heaters.
Meanwhile, the documentation in terms of assembly guides, power supply build examples, heatsinking worked examples is advanced but not complete. It's been quite an effort to prepare all these! Hoping to have a big finishing effort when I get back, and on with the release - I have plenty of PCBs stocked.
Apologies for the wait - I intend to offer a well-documented, well-supported offering, - thoroughly tested by the time it is released.
Rod