I'm building a SET KT88
Anybody can point me to a HV regulator for B+ using zener diode ?
How does it compare a regular CRCLC to a cap + voltage regulator + cap?
Thanks,
Alex
Anybody can point me to a HV regulator for B+ using zener diode ?
How does it compare a regular CRCLC to a cap + voltage regulator + cap?
Thanks,
Alex
High-voltage zenner diodes have too small dissipation power to handle such power requirements. You need to build full-blown regulated power supply if you want stabilized B+ voltage. T-Reg from Elektor 3/2009 is just fit perfectly your purpose.
Do you know how to build lower voltage regulator with zener element at the base/gate of pass transistor ? Well, replace zener for a string of higher voltage ones, makes sure you don't exceed their maximum dissipation and add a capacitor in parallel so that you get "soft start" effect of capacitance multiplier until your regulator hits zener breakdown voltage.
This works OK.
An externally hosted image should be here but it was not working when we last tested it.
You can build a better reg, but this one is simple and decent.
IRF820 perhaps?
Thank you for the schematic. Is it really necessary to add regulator module for vacuum tubes? For this amp I'm building B+ will be ~400V 175mA?
High voltage zeners have horrible tempdrift. The voltage will rise by several volts as temp goes up. I've found a simple voltage divider with just two resistors, buffered my a MOSFET, makes a better voltage regulator than zeners. Simpler as well.
If the voltage divider feeds into a large capacitor you also get the benefits of a slowly rising voltage, which give the circuit a nice comfy slow start up.
Or use a regulator tube, such as 0B2 or the likes. Reg-tubes might be noisy in high gain preamps, so may need a little filtering and buffering. U dont want to place a cap in parallel to a reg tube since it'll likely oscillate.
If the voltage divider feeds into a large capacitor you also get the benefits of a slowly rising voltage, which give the circuit a nice comfy slow start up.
Or use a regulator tube, such as 0B2 or the likes. Reg-tubes might be noisy in high gain preamps, so may need a little filtering and buffering. U dont want to place a cap in parallel to a reg tube since it'll likely oscillate.
Hmmm. I reread your original post, and realize u want regulation for the whole amp, and not just the pre-section. That case a voltage divider will drop too much voltage. Unless u've got lots to spare.
175mA is a lot, and a triode in SE has no benefits of a PP cancellation of power supply ripple.
If it were me, I'd use CLC and then experiment to a cap value that shunts some ripple to the cathode of the output tube. That trick works great. That cap should be the value of the cathode bypass cap, divided by the triode's mu.
SET amps usually have a little ripple noise, and usually it's low enough that most of us can live with it.
175mA is a lot, and a triode in SE has no benefits of a PP cancellation of power supply ripple.
If it were me, I'd use CLC and then experiment to a cap value that shunts some ripple to the cathode of the output tube. That trick works great. That cap should be the value of the cathode bypass cap, divided by the triode's mu.
SET amps usually have a little ripple noise, and usually it's low enough that most of us can live with it.
I didn't know zener diodes are so drifty...
I have designed in PSU II a CRCRC. B+ is 400V with 0.6mV P-P ripple. But I have 2 big caps and I wanted to get rid of them. I don't want to use choke for filtration. I guess I'll go back on my design. Thanks you SemperFi for the explanation.
Alex
It will be a big regulator dissipating plenty of power !
If you can read french see here:
Rgulateur Alimentation Haute Tension
But pentodes are largely insensitive to plate voltage, you just need to stabize screen voltage.
Yves.
I have 82uF / 250R / 820uF / 250R / 820uF
"Regulateur a haute tension" is interesting.
Thanks,
Alex
A couple of volts is what, 1% at worst, over the course of better part of an hour ?
Line voltage can deviate +/- 10% from nominal value (in some countries the interval is tighter though) in a matter of seconds and would still be perfectly within allowed margins.
Audio Research used a bunch of zeners in series to drive the grid of a 6550 in their D76 amplifier -- the schematic is here http://www.arcdb.ws/D76/ARC_D76_schematic.jpg -- the zeners like to be mounted above the circuit board so air can circulate.
Supertex makes a neat little regulator in TO-92 which you can configure to drive the base of a pass transistor. It's the LR8N3 and available from Mouser.
Supertex makes a neat little regulator in TO-92 which you can configure to drive the base of a pass transistor. It's the LR8N3 and available from Mouser.
It is available from Elektor and AudioXPress web site, search with "T-Reg" keyword. If you did not find it, please e-mail me. BTW, Elektor sells PCB boards for T-Reg.
True.
I still dont like them😉 Something we just dont like and other things we really like, even though either solution works. Makes it fun dont it?
If you want a silent supply, it can be done pretty easily with a MOSFET buffering a voltage divider. You only need to drop 10volts or so to make sure the reference voltage is below ripple.
The voltage divider can be made many ways, even with the help of zeners or some other combo of passive and active devices.
Sorry rambling on, and I have no circuit to show for...
I've got a SET amp I'd like to silence a bit more, and am concidering some of many options. If I only had time...
The voltage divider can be made many ways, even with the help of zeners or some other combo of passive and active devices.
Sorry rambling on, and I have no circuit to show for...
I've got a SET amp I'd like to silence a bit more, and am concidering some of many options. If I only had time...
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