I am considering assembling this 2E26 amp, what is your opinion on it:
https://www.r-type.org/articles/art-271.htm
https://www.r-type.org/articles/art-271.htm
My opinion is you will have fun.
Just for more fun, try triode wiring the 2E26. Connect the screen to the plate, using a resistor of 100 Ohms from screen to plate. You will need to increase the resistance of the cathode self bias resistor, R6, because the screen is now at 250V, the new max screen voltage spec. Then remove the negative feedback (remove R4 and C5, connect R3 lower end to ground. The power will be less. you can predict the damping factor, the plate and screen parallel impedance is about 1900 Ohms. Figure 5K primary/2k driving impedance, the damping factor is a little more than 2. With 10k primary, the damping factor is a little more than 4.
I did not remove R7, just to make rewiring as a beam power tube with negative feedback operation easier.
Triode operation will give less power, but should have low distortion, and is a simpler circuit. The damping factor is decent, without the need for negative feedback that is needed for beam power mode.
Let us know how both the Beam Power mode, and Triode mode work.
Nikon F is a 1959 classic. I have an old Nikon non-Ai 55mm f3.5 Macro that I love. I use adapters to mirrorless bodies.
Just for more fun, try triode wiring the 2E26. Connect the screen to the plate, using a resistor of 100 Ohms from screen to plate. You will need to increase the resistance of the cathode self bias resistor, R6, because the screen is now at 250V, the new max screen voltage spec. Then remove the negative feedback (remove R4 and C5, connect R3 lower end to ground. The power will be less. you can predict the damping factor, the plate and screen parallel impedance is about 1900 Ohms. Figure 5K primary/2k driving impedance, the damping factor is a little more than 2. With 10k primary, the damping factor is a little more than 4.
I did not remove R7, just to make rewiring as a beam power tube with negative feedback operation easier.
Triode operation will give less power, but should have low distortion, and is a simpler circuit. The damping factor is decent, without the need for negative feedback that is needed for beam power mode.
Let us know how both the Beam Power mode, and Triode mode work.
Nikon F is a 1959 classic. I have an old Nikon non-Ai 55mm f3.5 Macro that I love. I use adapters to mirrorless bodies.
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Been a Nikon F user since 1972, used the same F in high school(yearbook photographer), college(Brooks Institute of Photography) and as an Industrial/Scientific photographer. Still deciding if I want to build it.
View attachment 1473118View attachment 1473118
View attachment 1473118View attachment 1473118
The schematic shows a very ordinary plain Jane, SE amp.
Provided the resulting amplifier is operating OK, it will sound much
like any other amplifier on your speaker system. The speakers are the
limiting factor of performance in most all cases.
Some folks claim to have hearing ability from DC to Green Light.
Somehow they will get past the domination of loudspeaker distortion.
So build the amp, put on your favorite music or whatever.
And a beverage of your choice will enhance the experience.👍
My opinion. 🙂
2E26 makes a nice SE triode amplifier.
The BOM in the linked amp specifies 470K for the grid resistor. I think that's way too high - I used 220K when I was playing with 2E26 and this was satisfactory for all but one of my tubes, which would run away until I brought the grid resistance down to spec, which is 30K IIRC. My tube's are a mix of RCA and GE.
Win W5JAG
The BOM in the linked amp specifies 470K for the grid resistor. I think that's way too high - I used 220K when I was playing with 2E26 and this was satisfactory for all but one of my tubes, which would run away until I brought the grid resistance down to spec, which is 30K IIRC. My tube's are a mix of RCA and GE.
Win W5JAG
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