22 October 2007

EL84 Push Pull Tube Amplifier

Bruce's latest project, called the "OddWatt" is the EL84/6BQ5 Push-Pull Tube Amplifier shown below.

ECC802S SRPP / EL84 (6BQ5) Push-Pull Tube Amplifier
The driver stage is an SRPP circuit with ECC802S tubes, while ultra linear operation is used for the output stage with Sovtek EL84 tubes. LM317 Regulators are used to produce a constant current source (CCS) to set the bias of the output stage. The power and output transformers are from Edcor. 12VDC from a SMPS is used for the tube heater supply.

Bruce reports that performance from this amplifier is excellent. The low end extension is clean but not excessive. As expected, it has the characteristic tube warmth and is very easy to listen to.

DIY ECC802S SRPP / EL84 CCS Push-Pull Tube Amp Project
For additional information, pictures and schematics, see the complete page of Bruce's EL84 Push-Pull Tube Amplifier Project.

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05 October 2007

Synergy - LM3875 Gainclone Amplifier

Mark has been hanging out in the kitchen and has put together the Gainclone amplifier shown below.

LM3875 Gainclone Chip Amplifier
For the enclosure, Mark has used a heavy cast aluminum cooking pan and a massive wooden cutting board. The amplifier is based around the LM3875 chip (power opamp) and uses point-to-point wiring. The amplifier follows the
"rigid and compact" approach of the 47 Laboratory Gaincard amplifier. A rigid enclosure is used to reduce resonance and vibration while a short signal path, feedback loop and minimal parts (compact) are used to preserve information. The schematic of the three resistor amplifier is shown below.

LM3875 Gainclone Chip Amplifier Schematic
Keep cooking Mark, as I look forward to more of your projects. See the project page for full details of Mark's Synergy - LM3875 Gainclone Chip Amplifier Project.

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