Here's the information provided. It's pretty compelling. I wonder how it sounds. He seems very sincere.
"You are right in the schematic the heater is in AC. I did not had the time to redesign it. In reality the heater is in DC.
I know that you never saw a tube loaded like this. I don't know if I am the first or not (probably not), but I noted that the filament of an Edison's lamp is a perfect load. This filament, in fact, has a coefficient of resistivity in DC that is not fix, but depends from the voltage.
In other words, the filament keeps the current constant even if the voltage across the lamp changes. This characteristic is exactly what I needed, because the bias of the triode in DC will be locked and all the variations will be compensated. This is true till to some Hertz (6 or 7): after this frequency, because of thermic inertial, the filament behaves as a normal linear resistor. The lamp has another advantage: try to dissipate 50 Watts with a normal resistor...."
"You are right in the schematic the heater is in AC. I did not had the time to redesign it. In reality the heater is in DC.
I know that you never saw a tube loaded like this. I don't know if I am the first or not (probably not), but I noted that the filament of an Edison's lamp is a perfect load. This filament, in fact, has a coefficient of resistivity in DC that is not fix, but depends from the voltage.
In other words, the filament keeps the current constant even if the voltage across the lamp changes. This characteristic is exactly what I needed, because the bias of the triode in DC will be locked and all the variations will be compensated. This is true till to some Hertz (6 or 7): after this frequency, because of thermic inertial, the filament behaves as a normal linear resistor. The lamp has another advantage: try to dissipate 50 Watts with a normal resistor...."
No, it's a resistive load, not an inductor, and it's not very linear either if plate current varies sufficiently with signal to significantly modulate the hot resistance of the bulb. The tube amps I have heard with light bulb loads actually did not sound bad, but their output power and efficiency were low. I have seen more than a few around here, a passing fad about 7 - 8 yrs ago. 
These are considered an interesting perversion of the parafeed concept.
These are considered an interesting perversion of the parafeed concept.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.