Homemade EL34 6CA7 PP Stereo Tube Amplifier from Cathode to Fixed bias

YOUR LINK HERE:

http://youtube.com/watch?v=JEz8TJ2oUvY

The cathode biased 2 x 15 watt amplifier is made into a 2 x 33 watt fixed bias amplifier. Its not just the small changes to the circuit thats needed to be done in order to get the fixed bias working. • It ended up being a lot of work since I had to make a new high voltage power transformer and wind a bias coil on the old low voltage power transformer, plus the bias circuit itself.. • But now its done, and the amp is playing like everybody said it would with the tubes set 'hot' enough with the negative bias voltage; lower distortion and more output power + better bass response and sound in general. • The transformer-rebuilds was done from recycling old plates and its copper wires. Also the rotary switch and banana plug outlets + resistors and wires are from old trashed electronics. The money went to buy new tubes and the best tube-sockets money can buy. The multi-turn precision pots are a cheap Chinese product from e-bay.. Those pots are wired in a way that prevents contact faults in the pots to result in the bias voltage disappearing all together. If the pot mid pin looses contact with the carbon, then the bias circuit will work as a voltage splitter that makes the bias voltage to the tube set to about -35v instead of dropping to zero, making the tubes red-plating within seconds.. • Here is a video of this amp version 1. (with 2x15 watts and cathode bias) being made. The video also includes the important OPT design and how to use that software, and also where I got the recycled copper wires etc.+winding of the opt's: • • Homemade EL34/6ca7 Push Pull Tube amp...

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