Tube VS SS voltage regulators - any advantages?

[Wavebourn]

Foollowing the topic created by CarleBoy, I would like to open discussion to shed a light, if tube power regulators have some advantage over solid state voltage regulators. It is the first question, when some device has advantage, before answering how to build it.
I wanted to get the answer "why?" right in the topic "how?", but I am afraid the question may sink in a flame.

[astouffer]

Well if you accidently short the output of your solid state regulator it will have a very short lifespan. A tube will recover more gracefully.

I always wondered why no one has tried using a cheap transmitting tube like an 811A as a pass element. Its needs posetive grid bias so a solid state front end could drive it easily.

[Wavebourn]

Originally posted by astouffer
Well if you accidently short the output of your solid state regulator it will have a very short lifespan. A tube will recover more gracefully.

I always wondered why no one has tried using a cheap transmitting tube like an 811A as a pass element. Its needs posetive grid bias so a solid state front end could drive it easily.

One zener from source to the gate solves the problem more gracefully, without hot red plate and blown up pieces of cathode, but don't affect normal conditions:



To further limit the current you may move it's right leg through the R4 resistor.

[TUBESMAN]

this is a nice design for a regulator. Can I ask why no bypass cap on R5? From R5 to the base of Q2. That is common to reduce the HF impeadence of the supply.

The whole topic is like religion. You have the "God made man in his image" type (Only tubes in everything), the "There is a Higher Power and Evolution is how we came about" (Lets use SS diodes and transistors in non audio path areas) and "There is no God! Science Rules!" ( They are in the Solid State forum) . I hope you understand the point I make. I'd like an A/B/X test of the different PS regs.

[Miles Prower]

Originally posted by Wavebourn
Foollowing the topic created by CarleBoy, I would like to open discussion to shed a light, if tube power regulators have some advantage over solid state voltage regulators. It is the first question, when some device has advantage, before answering how to build it.
I wanted to get the answer "why?" right in the topic "how?", but I am afraid the question may sink in a flame.

• Glowey bottles coolness.
  
• No heat sinks several hundred volts above ground.
  
• VTs don't go "poof" nearly as easily.
  
• Gas discharge voltage references are more accuarte than HV Zeners, quieter, and the noise component is a good deal softer than reverse bias PN junction noise.

I always wondered why no one has tried using a cheap transmitting tube like an 811A as a pass element. Its needs posetive grid bias so a solid state front end could drive it easily.

Well, I am. The PS for the 845 amp I'm working on will use an 811 as a parallel regulator for the main plate supply.

[Wavebourn]

Originally posted by TUBESMAN
this is a nice design for a regulator. Can I ask why no bypass cap on R5? From R5 to the base of Q2. That is common to reduce the HF impeadence of the supply.

Yes, you may reduce own dynamic resistance on high frequencies of the regulator (without output capacitor), but in case of shorted output you'll get a pulse of voltage between base and emitter that may exceed 5V and damage the transistor. It is better to use output capacitor, anyway the regulator is far better than a passive filter with chokes and capacitors. But as soon as a diode present, you may use a capacitor. Also, one more zener may be used to limit maximum output current, as I described above, in this particular case 12V Zener will limit on about 50 mA, if to decrease resistor in source proportionally the limited current will be higher.

Also, the main feature of this regulator is a soft start. It was designed to power vacuum tubes. When tubes are cold they don't draw a current, and voltage on the output of the regulator goes up slowly; when tubes are hot and start drawing current due to positive feedback it increases output voltage untill it is stable. This regulator extends life of tubes powered by it, also it minimizes impact of transcient processes when switched on, despite it is so simple and contains very few elements.

Originally posted by Miles Prower

[list][*]Glowey bottles coolness.

I've asked about technical reasons.

[*]No heat sinks several hundred volts above ground.

Again, it is not a technical reason, nobody forces you to expowe high voltages. Insulation is cheap.

[*]VTs don't go "poof" nearly as easily.

Again, it is not a technical reason, but a style of handling. Tubes may be easily damaged as well. For example, they are fragile and may fall...

[*]Gas discharge voltage references are more accuarte than HV Zeners,

Please show any "less accurate" HV zener in my regulator. Zeners may be thermally compensated, unlike gas dischaarge stabilizers...

quieter, and the noise component is a good deal softer than reverse bias PN junction noise.

Again, it is not a technical reason, but result of poor usage. You are not forced to amplify noises, but you can easilly shunt them by capacitors. Also, you may use your gas discharge cool glowing tube with transistors. However, as the result you will get a peak of voltage while the gas discharge stabilizer starts, but anyway it is less dangerous than a broken tube that causes output voltage to be very high and unregulated.

Well, I am. The PS for the 845 amp I'm working on will use an 811 as a parallel regulator for the main plate supply.

And of course, you amplify noises, expose high voltages, and drop tubes from the table?

I don't think so...

[fdegrove]

Hi,

Why do I get the feeling there'll be plenty more racks in the pool.

Cheers,

[jarthel]

it is quite likely that people use tube regulation because on non-technical reasons?

SS are modern devices and as such would have the betters technical specs than tubes. so I think SS would possibly win hands down if the criteria is just based on technical specs.

[ray_moth]

I'm inclined to agree with jarthel here. One of the biggest disadvantages of series tube regulation I believe is the raher high plate-to-cathode voltage requirement, which means that you need a higher input voltage to a tube series regulator than you would with an SS series regulator, for a given output voltage and current draw.

Modern MOSFET devices seem able to work at realistic voltages for supplying tube circuits. Proper care in their use should not result in damage. Their high gain promises excellent regulation and the only possible downsides I can see to MOSFET regulation are the need for heatsinks and, possibly, more noise. Heatsinks can be provided safely, with a little skill, but I don't know enough about what noise could be introduced in MOSFETS and zeners to feel confident about how easily it could be overcome.

[TUBESMAN]

A heatsink and transistor will be smaller than a tube passing the same power. As far as noise, If you examine the formular for a voltage noise source, it shows the temperature of the object as one of the terms, so a tube has to have more noise.