tube for a shunt voltage regulator
the schematic is from raleigh audio: http://www.raleighaudio.com/ccs.htm
can I use any type of triode? daydreaming that I have a box full of WE 300b, can I use it for this application?
if not all tubes are suitable, can you give examples?
thank you.
the schematic is from raleigh audio: http://www.raleighaudio.com/ccs.htm
can I use any type of triode? daydreaming that I have a box full of WE 300b, can I use it for this application?
if not all tubes are suitable, can you give examples?
thank you.
Western Electric 274A tube early globe style may work well.
Also, you may use Telefunken ECC83 in parallel. 20 of matched pairs for the best sonic results.
Also, you may use Telefunken ECC83 in parallel. 20 of matched pairs for the best sonic results.
Jarthel, the type of tube needed for shunt regulation is dependant upon the current demanded by the load. The shunt tube will have to adjust its own current so that the sum of shunt current + load current is constant. It's easiest to assume that the shunt tube could have to draw the full current, if the load is open circtuit, and choose the shunt tube accordingly.
You certainly could take the approach recommended by Wavebourn but I think 20 pairs of ECC83 might be an expensive, unsightly and very space-consuming solution.
You certainly could take the approach recommended by Wavebourn but I think 20 pairs of ECC83 might be an expensive, unsightly and very space-consuming solution.
By the wey, a light bulb may be used instead of CCS. In such case we have already one glowing beauty, so a shunting regulator may be made from one HEXFET and a gas discharge tube between drain and gate, with a resistor between gate and drain.
Simplier, chiper, and more cool different glowings.
Simplier, chiper, and more cool different glowings.
Hi Jarthel,
There are two considerations when choosing a pass tube for the regulator.
First, as Ray mentioned, is to pick a tube that is capable of carrying the full current provided by the series element. You can use two halves of a dual triode in parallel.
Second is to make sure that the tube is capable of the plate-to-cathode voltage that it will see. To be safe, I always assume the full B+.
Dave
There are two considerations when choosing a pass tube for the regulator.
First, as Ray mentioned, is to pick a tube that is capable of carrying the full current provided by the series element. You can use two halves of a dual triode in parallel.
Second is to make sure that the tube is capable of the plate-to-cathode voltage that it will see. To be safe, I always assume the full B+.
Dave
Another consideration is that the tube chosen should bias in the active region without exceeding the voltage rating of the TL431.
Also true that the bias needs to be above the minimum required for the proper operation of the TL431 as well.. 😀
Seems like a nice solution. Suitable tubes could be ones like the 6BQ5, 12B4, 12BH7, 6BX7, 6CK4, etc. EL34 could be rather marginal at higher voltages. 300B, 6L6, and 6550 will exceed the 36V rating of the TL431..
I have used tube shunt regulators with zeners on the cathode as well - works ok with higher mu small signal triodes, and low currents only. Zener voltage was about 1/3 - 1/2 of the target voltage. (mu >20) The TL431 solution will perform a lot better where it can be used.
You can do something similar with higher bias types using a zener, npn transistor, tube cascode. Some additional gain will be provided by the npn depending on the pass tube's internal cathode resistance.
Also true that the bias needs to be above the minimum required for the proper operation of the TL431 as well.. 😀
Seems like a nice solution. Suitable tubes could be ones like the 6BQ5, 12B4, 12BH7, 6BX7, 6CK4, etc. EL34 could be rather marginal at higher voltages. 300B, 6L6, and 6550 will exceed the 36V rating of the TL431..
I have used tube shunt regulators with zeners on the cathode as well - works ok with higher mu small signal triodes, and low currents only. Zener voltage was about 1/3 - 1/2 of the target voltage. (mu >20) The TL431 solution will perform a lot better where it can be used.
You can do something similar with higher bias types using a zener, npn transistor, tube cascode. Some additional gain will be provided by the npn depending on the pass tube's internal cathode resistance.
...or take one FET, one Zener, and one resistor. No FET and resistor needed if the current is in the range of specs for a zener. Or take a P-channel FET and mount it directly on a chassis to eliminate heatsink. 😀
SY said:
Right. In that case, tie the screen to something lower. Anode can go anywhere (almost).
Simple tube shunt regulator
I've been using tube-type shunt regulators for several years, and have had good sonic results with them. The basic circuit is a high-transconductance pentode (typically a video amplifier tube) using its own gain to regulate. A filtered negative reference voltage is used. The regulation is not high, but if it is only used for one stage, never shared between channels, the results are good. With a little tweaking, the impedance vs frequency can be made essentially flat.
I've built this circuit with 6CL6, 6AG7, PL83, and the pentode section of a 6CX8. It would have better regulation with super-high transconductance tubes such as the 12GN7 or 7788, but I am somewhat allergic to frame-grid tubes in my circuits.
Here is a somewhat simplified version of the 2A3 amplifier circuit that I wrote about in Vacuum Tube Valley issue number 15. It is the one with RF-powered filaments. It is also one of the best-sounding amps I've built.
Simplified 2A3 amp
The top part of the schematic is a basic three-stage SE amplifier using a 5879, 2E24, and 2A3 (all pentodes triode connected). The 2.5V filament supply for the 2A3 is returned to ground through a current-sensing resistor. The 12AU7 is a cathode follower that is used to filter any hum or noise out of the -150V source. It also helps isolate this reference voltage between the two channels of the stereo amp. The 2.2K 10W resistor feeding the shunt regulator sets the gain of the regulator. If a higher voltage is available, a larger dropping resistor can be used, thus increasing the gain. I've tried using a choke here, but have run into stability problems. The 0.22uF cap across the 365K resistor allows the regulator to have full gain across the audio band. The 6CL6 screen is bypassed by a big capacitor. If you want even better stability at DC, a VR-tube could be used here.
- John Atwood
I've been using tube-type shunt regulators for several years, and have had good sonic results with them. The basic circuit is a high-transconductance pentode (typically a video amplifier tube) using its own gain to regulate. A filtered negative reference voltage is used. The regulation is not high, but if it is only used for one stage, never shared between channels, the results are good. With a little tweaking, the impedance vs frequency can be made essentially flat.
I've built this circuit with 6CL6, 6AG7, PL83, and the pentode section of a 6CX8. It would have better regulation with super-high transconductance tubes such as the 12GN7 or 7788, but I am somewhat allergic to frame-grid tubes in my circuits.
Here is a somewhat simplified version of the 2A3 amplifier circuit that I wrote about in Vacuum Tube Valley issue number 15. It is the one with RF-powered filaments. It is also one of the best-sounding amps I've built.
Simplified 2A3 amp
The top part of the schematic is a basic three-stage SE amplifier using a 5879, 2E24, and 2A3 (all pentodes triode connected). The 2.5V filament supply for the 2A3 is returned to ground through a current-sensing resistor. The 12AU7 is a cathode follower that is used to filter any hum or noise out of the -150V source. It also helps isolate this reference voltage between the two channels of the stereo amp. The 2.2K 10W resistor feeding the shunt regulator sets the gain of the regulator. If a higher voltage is available, a larger dropping resistor can be used, thus increasing the gain. I've tried using a choke here, but have run into stability problems. The 0.22uF cap across the 365K resistor allows the regulator to have full gain across the audio band. The 6CL6 screen is bypassed by a big capacitor. If you want even better stability at DC, a VR-tube could be used here.
- John Atwood
Jarthel,
I finish a 4 week stint in Cairns as support engineer on the Navy's Laser Airborne Depth Sounder today and fly home to Adelaide tomorrow. As far as I know I'm about the only guy in Adelaide who has the full Vaccuum Tube Valley collection so if you want to reference John's article give me a buzz Saturday or after (82693539).
I also recall that there was a series of articles on the TubeCad webpages about suitabilty of various tubes in voltage regulator circuits. They may have been talking about series regulators rather than shunt (don't recall) BUT any tube suitable as a series regulator device is also suitable as a shunt regulator device. Do a search on that web site.
Cheers,
Ian
I finish a 4 week stint in Cairns as support engineer on the Navy's Laser Airborne Depth Sounder today and fly home to Adelaide tomorrow. As far as I know I'm about the only guy in Adelaide who has the full Vaccuum Tube Valley collection so if you want to reference John's article give me a buzz Saturday or after (82693539).
I also recall that there was a series of articles on the TubeCad webpages about suitabilty of various tubes in voltage regulator circuits. They may have been talking about series regulators rather than shunt (don't recall) BUT any tube suitable as a series regulator device is also suitable as a shunt regulator device. Do a search on that web site.
Cheers,
Ian
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