Hi does anyone has experience with the 4PR65A tube as a single ended amplifier?
Its supposed to generate 15w in triode. There's a amplifier on sale that has rectified with ey500 and ecc40 is input tube.
I'm not sure what to expect. Someone has built this and im going to listen to it tomorrow 🙂. Its for sale for €600.
Im not experienced in diy, so Love to hear your opinions and experiences and tips on what to check when auditioning. 🙏
Its supposed to generate 15w in triode. There's a amplifier on sale that has rectified with ey500 and ecc40 is input tube.
I'm not sure what to expect. Someone has built this and im going to listen to it tomorrow 🙂. Its for sale for €600.
Im not experienced in diy, so Love to hear your opinions and experiences and tips on what to check when auditioning. 🙏
Are you talking about the Eimac 4-65A Tetrode tube?
Screen max 600V B+
Screen max dissipation 10 Watts
Plate max 2500V B+
Plate max dissipation 65 Watts
A 4-65A that is Triode wired (connect the screen to the plate through a 100 Ohm resistor).
In that case, now you are limited to 600V max.
Note: If the plate and screen have 600V B+, then when the tube is near cut-off, the plate and screen will be at 1200V.
Note: the 4-65A is a Tetrode; it is not a Beam Power tube, it is not a Pentode (no 5th element that Beam Power tubes and Pentode tubes have).
However, g1 birdcage grid, and g2 birdcage screen are lined up for 'beams' of electrons from the filament to the plate.
I built a single ended 4-65A, using only the screen (10 Watt dissipation), but I only had about 400V B+.
I used it in Triode Wired mode, and also with the plate grounded, the same results; I needed 500 or 600V B+.
The 4-65A looks beautiful!
Screen max 600V B+
Screen max dissipation 10 Watts
Plate max 2500V B+
Plate max dissipation 65 Watts
A 4-65A that is Triode wired (connect the screen to the plate through a 100 Ohm resistor).
In that case, now you are limited to 600V max.
Note: If the plate and screen have 600V B+, then when the tube is near cut-off, the plate and screen will be at 1200V.
Note: the 4-65A is a Tetrode; it is not a Beam Power tube, it is not a Pentode (no 5th element that Beam Power tubes and Pentode tubes have).
However, g1 birdcage grid, and g2 birdcage screen are lined up for 'beams' of electrons from the filament to the plate.
I built a single ended 4-65A, using only the screen (10 Watt dissipation), but I only had about 400V B+.
I used it in Triode Wired mode, and also with the plate grounded, the same results; I needed 500 or 600V B+.
The 4-65A looks beautiful!
If you use the 4PR65A, or the 4-65A for Class A service, the ratings are very similar.
Single Ended is Class A service.
4PR65A is for Pulsed Service, much higher voltages, much higher current, but only at a very low duty cycle.
But the continuous dissipation of the plate and the screen are the same as the 4-65A.
It might be possible to use the 4PR65A to create an audio Class D amplifier, but with pulse voltages up to 15kV, and pulse currents of up to 1 Amp it would be a nightmare to do that (you better get knowledgeable about things like Class C RF Transmitter service and/or Radar Modulator service).
Pulse transformer, or Pi Network anybody?
Why would anybody want to do that?
Instead, use the 4PR65A exactly the same way you would use a 4-65A for single ended audio service.
Single Ended is Class A service.
4PR65A is for Pulsed Service, much higher voltages, much higher current, but only at a very low duty cycle.
But the continuous dissipation of the plate and the screen are the same as the 4-65A.
It might be possible to use the 4PR65A to create an audio Class D amplifier, but with pulse voltages up to 15kV, and pulse currents of up to 1 Amp it would be a nightmare to do that (you better get knowledgeable about things like Class C RF Transmitter service and/or Radar Modulator service).
Pulse transformer, or Pi Network anybody?
Why would anybody want to do that?
Instead, use the 4PR65A exactly the same way you would use a 4-65A for single ended audio service.
Last edited:
waldorfs,
How did the amplifier sound?
Did you purchase the amplifier?
Please let us know.
I think many of us would like to know; regardless of a few bits of extra server space.
Whether you plug in 4PR65A tubes or 4-65A tubes, it should sound the same.
(hardly anybody would design an audio amplifier to only use 4PR65A tubes, and not also use 4-65A tubes too.
How did the amplifier sound?
Did you purchase the amplifier?
Please let us know.
I think many of us would like to know; regardless of a few bits of extra server space.
Whether you plug in 4PR65A tubes or 4-65A tubes, it should sound the same.
(hardly anybody would design an audio amplifier to only use 4PR65A tubes, and not also use 4-65A tubes too.