The maximum output power (clipping) is 14W (when the screen consumption of FU50 is 37W), the damping coefficient is around 4-5 (although I think damping is not important, this is another topic), the distortion of 5W is about 0.5%, and the distortion of 10W is about 1.8%The red font on the circuit represents the working points measured in practice. So this circuit has these characteristics:-Maximize the scope for selection and management to reduce opportunities for JS to hype specific models-Open loop circuit, more friendly to output transformer-More combinations and combinations for easy gallbladder replacement fun-Minimize the use of transistors as much as possible, facilitate construction, and be friendly to beginners. Because in fact, both stacked and unordered can be partially replaced with JFET or MOS transistors. However, there are not many opportunities to purchase genuine products domestically, and MOS is even less friendly to beginners in welding and installation. Nevertheless, it is still unavoidable to use MOS transistors for voltage reduction in the grid grid power supply.-Try to use impedance compatible output transformers for easy modification of old machines.-Try to use self-sufficient bias to facilitate direct replacement of power tubes. Still, I do not object to the modification. If possible, you can change it to a fixed bias for self-sufficiency, but please also modify the power supply voltage together.-Regarding C3, it also affects low-frequency transients and frequency responses, and if possible, you can try it yourself. The implementation uses a 4.7uF capacitor.-Regarding the feedback quantity, R14=470K is a moderate feedback quantity. If a resistance value between 330K and 430K is used, there will be more changes and distortion will be reduced. Let's try it out for yourself.
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Damping factor 4-5 with FU50 in pentode mode, no gNF (only Schade local fb), 3.5K primary impedance? I'd be very surprised if that is true.
If you do not want to use a MOSFET for the 245V screen supply, then . . .
Use an OD3, 150V + an OB3 90V in series.
240V is close enough to 245V, series gas regulator tubes are Simpler.
No MOSFET heatsink needed; no Anti-Static provisions needed, just a series power resistor from 410V B+ to the top gas regulator.
You will also need a start resistor across one of the regulator tubes (total 4 parts, simple).
And with OD3 and OB3 . . . you get two beautifully glowing shoulder tubes (Octal sockets).
Have fun building, listening, and WATCHING!
Note: 14 Watts output and 37 Watts output tube dissipation is 38% efficiency. That is good for a Single Ended circuit.
(don't forget about the output transformer insertion loss; Example: 0.5 dB takes 14 Watts input, and Presto Chango, you get 12.5 watts out)
Just my opinions
Use an OD3, 150V + an OB3 90V in series.
240V is close enough to 245V, series gas regulator tubes are Simpler.
No MOSFET heatsink needed; no Anti-Static provisions needed, just a series power resistor from 410V B+ to the top gas regulator.
You will also need a start resistor across one of the regulator tubes (total 4 parts, simple).
And with OD3 and OB3 . . . you get two beautifully glowing shoulder tubes (Octal sockets).
Have fun building, listening, and WATCHING!
Note: 14 Watts output and 37 Watts output tube dissipation is 38% efficiency. That is good for a Single Ended circuit.
(don't forget about the output transformer insertion loss; Example: 0.5 dB takes 14 Watts input, and Presto Chango, you get 12.5 watts out)
Just my opinions
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Thank you to the administrator for helping with the editing, and thank you for your reply support.
这个电路我做过，性能非常好，听感也超级棒！是值得大家一试的机器。下面链接是我的制作过程。
http://bbs.hifidiy.net/forum.php?mod=viewthread&tid=1496593&extra=page=1
http://bbs.hifidiy.net/forum.php?mod=viewthread&tid=1496593&extra=page=1
R3 1k and C4 100 pF appear to be a low pass filter to 'round out' a fast rise square wave test signal. The filter has a Gaussian response, 0.35 factor.
It appears to be there to prevent the amplifier output from "Ringing", if in fact there is supersonic ringing of the rest of the amplifier circuit and parts).
R3 is Not a grid stopper resistor, because C4, 100 pF is directly from the grid to ground.
In order to have a grid stopper resistor there, you need to add a 1k resistor connected between C4 100pF and the grid.
Look carefully: At Power-Up, if the B+ rises before the amplifier tubes warm up, then C1, 0.22u 400V will be subjected to More than 400V.
I hope that capacitor is self-healing.
Put a 600V or 630V rated capacitor there.
I would not count on the warm-up timing of the 5AR4 versus the warm-up timing of the 6SN7 and FU50.
Don't forget about Hot Starts, the timing is critical there too (which tube cooled off faster before Hot Start power is restored).
Your Mileage May Vary.
And why is it that an input capacitor is rated at 500V, but the caps after the choke are only rated at 450V?
Again, what about Hot Starts.
Be sure to look at the B+ at normal power-up, and also at Hot Starts.
Save money and use the lowest rated parts available.
Or,
Go for reliability.
Just my opinions and my experience.
It appears to be there to prevent the amplifier output from "Ringing", if in fact there is supersonic ringing of the rest of the amplifier circuit and parts).
R3 is Not a grid stopper resistor, because C4, 100 pF is directly from the grid to ground.
In order to have a grid stopper resistor there, you need to add a 1k resistor connected between C4 100pF and the grid.
Look carefully: At Power-Up, if the B+ rises before the amplifier tubes warm up, then C1, 0.22u 400V will be subjected to More than 400V.
I hope that capacitor is self-healing.
Put a 600V or 630V rated capacitor there.
I would not count on the warm-up timing of the 5AR4 versus the warm-up timing of the 6SN7 and FU50.
Don't forget about Hot Starts, the timing is critical there too (which tube cooled off faster before Hot Start power is restored).
Your Mileage May Vary.
And why is it that an input capacitor is rated at 500V, but the caps after the choke are only rated at 450V?
Again, what about Hot Starts.
Be sure to look at the B+ at normal power-up, and also at Hot Starts.
Save money and use the lowest rated parts available.
Or,
Go for reliability.
Just my opinions and my experience.
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