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Building a Valve Amplifier Part 4: Two Channels and a Power Supply
Dave Ives
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I currently look after production at AB Open. I have a background in the arts, environmental conservation and IT support. In my spare time I do a bit of DJing and I like making things.

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November 20, 2019 09:18

Just a quick background, I have designed and built many valve amplifiers in my time.
To help with those building one, I think I should point out a special difference between transistor and valve amplifiers: Transistor amplifiers are voltage output and as such are happy with an open circuit output when testing, but a short circuit on the speaker terminals can quickly kill the amplifier; a valve amplifier on the other hand is a current driven output and the amplifier is happy with a short circuit on the speaker terminals, but if you leave them open circuit this can damage your output valves due to the excessive voltages generated by the output transformer. In short - when testing the valve amplifier ALWAYS provide a load even if it is just a resistor (similar to the impedance rating of the speaker). Good luck to all of you building one of these amplifiers.

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November 21, 2019 09:59

@pauljolly interesting! I hadn't appreciated that and good to know.

November 19, 2019 08:39

I like the way you take large steps, but not too large. Great photos and comments, and some play-by-play experiences. Some people dredge up ancient designs with mystery parts (where to find these?) but yours is all off-the-shelf. Great to see.

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