• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

have a pair of 5k:8 OPTs lying around.. suggest me something to build?

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Heck, why not a 2A3? That's an easy to drive DHT, and sounds really nice when hooked up well. You could use a +300V supply, cathode bias it. 2A3 with about +250V at anode, about -45V at grid, about 60mA thru it, 5k OPT load. That's close to the classic operating point, except with a higher than normal anode load (lower distortion, less power out). Figure maybe 3W out.

Drive it with something like a ECC99 or 5687, or a 6SN7. DC-couple two halves together, RC-coupled to the 2A3 grid.

Even a 5842 should be able to drive a 2A3 well enough, no?

Add a volume control and input selector switch and make a sensitive-enough two-stage "integrated amp."

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A 300B runs well at 375-ish Volt B+ and 60 mA anode current. You'll get around 5 Watt out with fairly low distortion. I have one running in that configuration and it sounds good to my ears.

Yeah....what he said. I have a Tubelab SE with 5K Electra Print OPT's. It is the best sounding amp that I have with 45's in it but only makes 2 watts. The B+ is about 325 volts. I run 300B's in the same amp and get about 5 watts. The sound is very good but I prefer the 45's.

On a lighter budget the Simple SE or any similar circuit with 400 volts or more of B+ works great with 5K OPT's. You can run EL34's or 6L6GC's at 60 mA and they work great. KT88's seem to prefer a bit more current.
 
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