I've been researching tube regulators (series), and they all seem to top out at a few hundred milliamps. I'm looking to regulate the entire B+ of an amplifier, 600V at 1A. I know it won't be simple, but this whole amp has an "over the top" theme to it. Primary function of the regulator here is ripple rejection, and thus saving weight/money on chokes.
I use a "go to" circuit that does quite well for most things, and has fantastic ripple rejection. The power supply section will be different from what is shown on that page, but everything from the reference tubes onward is the same. Circuit can be found below. Tube Based Voltage Regulators - Part 3
I had two thoughts in mind: parallel pass tubes, or an 813.
Either way the "raw" B+ would be about 800v, and resistors/caps would of course be rated for the increased dissipation/voltage across them.
My question is, assuming the pass tubes are well matched, can the 6bm8 drive more than one, and will the 105v supply on the plate of the error amplifier be enough at the higher voltage? A similar question applies to the 813, do I need to increase the plate voltage on the error amplifier to drive it, and if I do, would I have to change the error amplifier circuit values?
Thanks,
Nick
I use a "go to" circuit that does quite well for most things, and has fantastic ripple rejection. The power supply section will be different from what is shown on that page, but everything from the reference tubes onward is the same. Circuit can be found below. Tube Based Voltage Regulators - Part 3
I had two thoughts in mind: parallel pass tubes, or an 813.
Either way the "raw" B+ would be about 800v, and resistors/caps would of course be rated for the increased dissipation/voltage across them.
My question is, assuming the pass tubes are well matched, can the 6bm8 drive more than one, and will the 105v supply on the plate of the error amplifier be enough at the higher voltage? A similar question applies to the 813, do I need to increase the plate voltage on the error amplifier to drive it, and if I do, would I have to change the error amplifier circuit values?
Thanks,
Nick
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From what I have gathered, yes. The same way an el509 can pass 350mA in the original circuit. My guess is that since it is just "passing" the current, much less is dissipated in the plate. Im thinking plate dissipation is the real limit here. You'll notice that the current capability decreases as the output voltage gets farther away from 350v, presumably because more is being dissipated in the plate. Tube regulators seem to be happiest dropping about 150v.
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For continuous service, the current limit for an 813 is listed around/below 200mA. Far from an amp.
The EL/PL509 has a much higher max current spec: 500mA.
You need to look at both ratings to determine the max current.
The EL/PL509 has a much higher max current spec: 500mA.
You need to look at both ratings to determine the max current.
I suggest you to study Radiotron Designers Handbook (4th edition) from page 1215 to 1222. This part of the book deals with valve voltage regulators including the design process.
RDH 4th edition can be downloaded free of charge.
RDH 4th edition can be downloaded free of charge.
At a glance: you want to lose 200V at 1 Amp, so need 200 Watts plate dissipation.
And you need to pass 1 Amp at 200V, so you need a 200 Ohm plate resistance.
As said, 813 is rated for 0.180-0.225A max, also 100-125W max dissipation. You are going to need more than one.
Is 813 even a good choice? Triode curves show 100mA needs 200V drop, so you need TEN of them to pass 1 Amp, and are using <25% of the Pdiss you paid for.
You really want a lower-Mu pass tube.
The GO-TO pass tube was the wretched 6080/6AS7. 125mA 13W/section, twin triode.... you need 4 bottles for current, 8 bottles for dissipation. There ARE 2X bigger twin-triodes but today more than 2X the cost.
USSR MIG radar used the 6C33C-B pass-tube and they sell for $60. 300mA, 60W, three bottles almost does the job. There's about a hundred Watts just in heaters for three jugs.
I don't think you will come close. There was a (small!) pass-tube specifically aimed as a choke-replacement but I have never seen one, sales or pictures. Even their own math made it kinda a split decision. You save a dime and a couple ounces but you have to replace tubes.
Thanks Artosalo! After reading that section, I'm not sure what to think. An EL509 has a cathode current rating of 500mA, whilst in the typical operation section the plate current is given as 100mA. What would be truly helpful would be a plate current spec on the EL509. Cathode current is quite misleading.
I was looking into this in the past, and was looking at a 4-1000A because of its high plate current rating nearing 1A. I was told that because I was running it far below max voltage, I could increase plate current considerably beyond 1A without exceeding dissipation limits. As far as I can tell, 1A at 800v would not exceed dissipation limits for an 813 in a pass tube application. Note this will rarely actually pull 1A. That's allowing for 250mA per kt150, which is above their rating. I just want a stout power supply.
I've seen an 813, and all of the plate leads look thick enough that 1A flowing through them would not cause resistive heating to be a problem. Therefore the killer would be dissipation. Are there any tubes that have a plate current rating of 1A?
I was looking into this in the past, and was looking at a 4-1000A because of its high plate current rating nearing 1A. I was told that because I was running it far below max voltage, I could increase plate current considerably beyond 1A without exceeding dissipation limits. As far as I can tell, 1A at 800v would not exceed dissipation limits for an 813 in a pass tube application. Note this will rarely actually pull 1A. That's allowing for 250mA per kt150, which is above their rating. I just want a stout power supply.
I've seen an 813, and all of the plate leads look thick enough that 1A flowing through them would not cause resistive heating to be a problem. Therefore the killer would be dissipation. Are there any tubes that have a plate current rating of 1A?
I don't know why, but I was thinking the 813 had 200w plate dissipation rating.
Note that I'm not triode connecting it, so I'm not sure if the triode curve applies. I'll definitely look into that Russian tube though.
Also, using a triode would require a complete alteration of the circuit, and I'm not really confident enough to do that just yet.
Any regulator will definitely save weight, since I won't need as much filtering on the input.
Note that I'm not triode connecting it, so I'm not sure if the triode curve applies. I'll definitely look into that Russian tube though.
Also, using a triode would require a complete alteration of the circuit, and I'm not really confident enough to do that just yet.
Any regulator will definitely save weight, since I won't need as much filtering on the input.
The plates of any of the mentioned types can pass several amps of current, not much different than a piece of wire. As long as the dissipation limit is not exceeded that is (current x voltage).
The thing is, if the cathode can't produce enough electrons, it ain't gonna happen.
The PL519 has a cathode that safely delivers 0.5 amps continuously and 1.5 amps peak.
If you design around a smaller voltage drop so you stay within 40W dissipation, you may get away with a single PL519 to get your desired 1+ amps peak capability. There are US types that can do that as well.
The thing is, if the cathode can't produce enough electrons, it ain't gonna happen.
The PL519 has a cathode that safely delivers 0.5 amps continuously and 1.5 amps peak.
If you design around a smaller voltage drop so you stay within 40W dissipation, you may get away with a single PL519 to get your desired 1+ amps peak capability. There are US types that can do that as well.
It will likely experience .75A continuous, so I'd still need more. Is paralleling 2 or 3 EL509s feasible?
Absolutely yes. Several old school manufactures of tube based power supplys did this a lot. Kepco, Lambda and Electronic Measurments all did it. Kepco liked 6336's, Lambda used 5881's (aka 6L6WGB) and EM used 6550/KT88's. I own several of each of these (boat anchor) supplies.
What is needed to make sure they share current evenly? I know the goal is to have as low a resistance as possible, so I wouldn't imagine plate resistors.
An 813 needs about 400V on its g2 to pass 200 mA. Now if the plate is only 200V, then the screen is going to catch more than its share and will overheat.
cheers,
Douglas
cheers,
Douglas
If I were to use an 813, it'd have 800v on the plate. Im leaning toward parallel EL509s at the moment though.
6C33C is specified to 600mA continous and even though you connect 2 in parallel with derating they can handle 1A together, see here page 6 http://www.jogis-roehrenbude.de/Russian/6C33C/6C33C-B-6S33S-VExtendedDatasheetMB.pdf
But! Ensure good cooling so you don't overheat the sockets.
Now that I've read the spec sheet, it has a max plate voltage of 450v. I'll be running near twice that, so that rules out that tube.
For a regulator the pass tube only need to handle the difference between input raw DC voltage and regulated output voltage, you mention 800V in and 600V out so a 6C33C is more than OK
That's good to know, definitely opens up possibilities for different pass tubes. Though being that it draws as much filament current as 4 EL509s, I'm inclined to stick with them, especially since other regulators in the amplifier are using them.
Why a 200V drop over the regulator?
Drop less and your pass tubes run cooler and last longer. Better for the electricity bill as well.
Drop less and your pass tubes run cooler and last longer. Better for the electricity bill as well.
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