Bruce project, is a EL84/6BQ5 Push-Pull Tube Amplifier. The driver stage is an SRPP with ECC802S tubes, while ultra linear operation is used for the output stage with Sovtek EL84 tubes. LM317 Regulators are used for constant current sources CCS of the output stages. 12VDC is used for the tube heaters.
EL84 Push-Pull Design Concepts
Tube Amp Features:
DC heater supply by a 12 volt SMPS.
Ultra linear operation of the output stage with Sovtek EL84 tubes.
SRPP driver stage with ECC802S tubes.
Provision for tube balancing.
Constant current sources for the output stages using LM317 Regulators.
Relay control of the B+.
Minimum component count in the amplifier stages.
Tube Amp Heater Power Supply
The heaters are supplied with a regulated DC supply provided by an off the shelf switch mode power supply (SMPS). The SMPS is rated at 12VDC / 3A. The output is quite clean . Each channel was wired for 6V heaters. The center point was returned to the main system ground. This made one set of heaters positive to the ground and one negative.The SMPS also provides power to the indicator lamps and B+ switching relay.
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