• 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.

47 pentode...fabulous sound !!!!

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I love the triode sound ! :D
But I did some experiments with the old 47 pentode in pentode mode, single ended class A and...WOW !!! :eek:
The sound is very nice, very detailed, with good bass and treble and a wonderful medium response, the voice and rhythms are very clear !
I use a Tesla E180F in triode mode as pre amplifier and a Edcor transformer in output. My experimental speaker is a cardboard open baffle, with a Trusonic FR80 speaker and a Foster horn.
Watch the video, sorry for the mess in my prototype and the bad video ... but my free time is small!

Raytheon 47 pentode in Single ended mode - YouTube

Aldovan
 
very nice! thanks for sharing

Thanks !
This is my basic project. It use a 330V power supply and I do not test, yet.
The prototype is working with a 280V power supply.
The schematic is very simple and easy for make. :)


Aldovan
 

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resistor

What is the purpose of 1k2 resistor in series with primary of OPT?

Only reduce the plate voltage.
The 47 have a maximum voltage of 250V.
This resistor do not is necessary if you use the correct plate voltage.
But the 6DQ3 rectifier have a low drop voltage.
The rectification is by solid state diodes and the 6DQ3 is used for a soft high voltage start, only.

Aldovan
 
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