This preamp is dht output.german pentode in first stage .tube + mosfet in power supplay. pentode+triode in active riaa phono .
When I decided to build the phono stage for this preamp... I couldn't find any circuit for ecf80. so i start to build by pentode in first and triode 2nd stage.
i used mullard ecf80 .
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i used mullard ecf80 .
Thanks for your good work, I was looking for an active riaa one. Look at my circuit . In Russian sites, you can find some ecf80 phono circuit . ..passive riaa networke .
For the filament of 6b4g... a dht regulator circuit was made. An Inductors was used in the raw voltage circuit .The stability of filament regulator was excellent. But the hum does not come only from the filament . It seems that building a tube circuit in a wooden box is not a very interesting idea. Even building a tube circuit as a test on a board does not give real results.
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test filament reg of russian 6b4g..
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https://iranaudiotube.blogfa.com/
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test filament reg of russian 6b4g..
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https://iranaudiotube.blogfa.com/
For the best project, need to have known tubes. . I collected tubes . I have about 50 of new el34 tubes....Mollard...telefunken . rft....japan made.
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gain of green dht preamp = 15 .this dht preamp has tow sections. i think ... single-stage tube preamp is more of a hobby circuit.
10 khz in dht preamp
aftter hf switch on .....10 khz was changed
10 khz in dht preamp
aftter hf switch on .....10 khz was changed