• 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.

Subminiature tubes/valves for Hi-FI

@b_force
I tried, initially, to use a 7806 for the heaters but that thing got really, really hot. Then I had the idea of placing an external power transistor to help the regulator, but never got the balance between the two right. The problem is that, if I use a 12V power supply, I will have 6V drop across the 7806 and both valves are pulling 700mA or so. Finally, I gave up and used a buck, which runs cool. 😎
That doesn't surprise me if you were using a 12V power supply.
That is (12-6)*0.7=4.2W of power dissipation.

With a buck converter that is more around 630mW or so.
 
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@b_force
By the way, after what you said regarding the 6021, I had a look to the curves and said holly crap, I really messed up.
Went to ebay again and the seller exchanged that one for a 6AK6. UUUuufff (he didn't have EL91/95).
I will try it, as you suggested, as a replacement for the 6P30B-R which consumes more than 400mA of current.
 
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My take on subminiature tube preamp. Differential, high gain, high current, low distortion. I'm also planning to use SMPS for the heaters one of these days, I already have the converters.
 

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