• 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.

Gold mine of DI¥ audio tubes schematics from Japan

Good point in diy spirit you can open dedicated thread about this amplifier and share your better creative solution.
Is for inspire your way of making ;)
All tubes projects was build by Diyers , tested and work amplifiers.
Is not virtual software simulation is verified true analog only.
Sure not perfect for every body but generous gifts :up::):wrench:
 

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He must be a crazy guy. He wrote some crazy experiments and circuits in his website. Worth reading or even looking pictures.
http://our-house.jp/vtm/index.htm

I want to try reducing heater power he trying if it does not much shorten valve life. How do you guys think? If the space charge is too less for the anode current,the cathode will be damaged by itself or the contaminated ion, IIRC? But how much? current, heater power, cathode thermal resistance and cathode temperature? In fact it should be avoided, I suppose...
 
I guess there is a limit, e.g, 15%, on how much you can lower the filament voltage before shortening the life of the tube. I think his experiments basically confirmed what the old texts said.

Thank you. I found old Hitachi's article on the internet. Although it is very small voltage and current amplification application, it suggest operationg point of 12AX7
Ip 1mA Vh 6.3V or 12.6V
Ip 100uA Vh 4.5V or 9.0V
Ip 10uA Vh 3.4V or 6.8V
This is more steep change than I thought. Lowering heater voltage seems not a good thing.
 
I do make little exception and show Tamasan 22 Diy works :
Tamasan 22
We can find few schematics inside of his blog but not so many.
Amplifiers are from tiny battery powered , OTL's to huge transmitter tubes monsters.
Extraordinary and out of limits. Attention !!!! :D
 

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