Hi guys, I tested a new SE amplifier with 300b and a mu folower type driver with D3a and EL802, DC final tube filament supply, anode voltage 420v, bias current 85mA, OT impendance-5.2K/8 ohm and a servobias system for bias regulation. All transformers are built by me and soon I will start building the chassis
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That sounds interesting! Will you post the schematic eventually? What kind of PS did you go with?
Rod,
I am still interested in your cap multiplier PS. Emailed you a few months back.
Rod,
I am still interested in your cap multiplier PS. Emailed you a few months back.
This is the designed and verified scheme, driver distortion is less than 0.2%/70v a.c. required for 300b tube and amplifier output power is 7w with a THD <3%. Operating stability is ensured by the correction loop of the servobias system and by stabilizing the anode voltage
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This is very courageous, and require adequat equipment to do so ! Congratulations...
T
The output transformers have oriented grain core, 6P+4S+KFB, L=23 H, Llk=5.1mH R=200 ohm, 18Hz/-1dB-52.6Khz/-1dB. For the network transformers I chose the solution to divide the power part on three transformers distributed more easily on the chassis and the shock coil has 5H/320mA/40 ohm
With some properly implemented GNFB, THD could easily be decreased even more.
Best regards!
I guess any small signal transistor will serve well as current limiter.
Best regards!
Best regards!
I assume, that 0R68 resistor in filament supply is used for setting current limit, but according Ube=0,7V/0R68 is only a little above 1A, not to few for 300B (1,2A nominal)?
I just building 300B SE too, so it is nice circuitry of filament supply.
I just building 300B SE too, so it is nice circuitry of filament supply.
The Ube voltage can be 0.6v-0.7v, therefore the resistor can be chosen experimentally so that the voltage on the filament of the 300b tube is 5v
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