An externally hosted image should be here but it was not working when we last tested it.
has anybody heard one? i wonder why such a simple circuitry did not become popular?
pretty obvious if you look at the o/p tube and it's availability / price and the o/p power that can be excpected from one which if my memory serves me right is miniscule even back in the days of sound practices they were a right rare tube to get even used the price was pretty substantial [ if you could find one!] cheers TC
Re: can this be scaled up?
No go! You can use voltage regulators in series, but not in parallel.
Regards
Ralf
AudioGeek said:what is the possibility of it being scaled up to say a 300B circuit using parallel VR tubes in the cathode?
No go! You can use voltage regulators in series, but not in parallel.
Regards
Ralf
well if you can find some used 45's at a reasonable price, it is a very simple circuit and using the hammond 125 e op xfrm it may be a nice and simple amp to build BUT I would use the hammond 125 se as being a better choice and by all accounts performs quite well in 2a3 se circuits. cheers TC
Re: can this be scaled up?
Konnichiwa,
Not directly, but by combining a VR Valve AND something like a KT88 you can make a "power shunt regulator that keeps the voltage on the KT88 Anode quite constant. Then apply a choke with an apropriate series resistorto load the driver and bias the output valve, voila, done. But a resistor/capacitor parallel combo in the output cathode will do not really any worse, if the capcitor is high quality or perhaps WE/UP connection is employed.
Sayonara
Konnichiwa,
AudioGeek said:what is the possibility of it being scaled up to say a 300B circuit using parallel VR tubes in the cathode?
Not directly, but by combining a VR Valve AND something like a KT88 you can make a "power shunt regulator that keeps the voltage on the KT88 Anode quite constant. Then apply a choke with an apropriate series resistorto load the driver and bias the output valve, voila, done. But a resistor/capacitor parallel combo in the output cathode will do not really any worse, if the capcitor is high quality or perhaps WE/UP connection is employed.
Sayonara
Surely it is a bit dangerous to run the 45 tube with this direct coupled configuration.
I would prefer running it with the RC coupled and it is almost fail safe.
I believe the VR might cause some more noise and distortion in comparison with cathode resistor with bypassed capacitor. Just a guess.
Johnny
I would prefer running it with the RC coupled and it is almost fail safe.
I believe the VR might cause some more noise and distortion in comparison with cathode resistor with bypassed capacitor. Just a guess.
Johnny
rdf said:Also, as drawn the VR tube is within 4 ma of its maximum current. Wouldn't the 0D3 would be operating well outside of spec at anything above very low output levels?
i thought i saw someone else raise the same concern on another forum.
thanks
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