Hello!
If I want to add gas tube to the existing power supply for 300v B+ regulation. Between 2x0A2 and 2x0D3, which one would be your choice for Aikido 6SN7?
Thanks!
If I want to add gas tube to the existing power supply for 300v B+ regulation. Between 2x0A2 and 2x0D3, which one would be your choice for Aikido 6SN7?
Thanks!
How much total current can the supply furnish? Usually, two OA2 in series with 100 k equalizing resistors across each tube works well. Two OD3 in series with 100 k equalizing resistors will regulate slightly more current. The series resistor value is dependent on the unregulated source voltage, the total current draw, and the "overhead" current through the regulator tubes...
OA2 needs a breakdown voltage of 165v, from my STC application report - "The initial supply voltage should exceed breakdown voltage to ensure rapid striking" In other words your supply voltage need to be higher than 300v.
You'll also need a big resistor to limit current, you find the value by adding load current to voltage regulator current,for the OA2 that's at least 5mA. That's a lot of heat inside your chassis.
Apart from them looking nice VR valves on their own do a brilliant job of regulation, there's no fold back. As part of a regulated supply though they're better.
You'll also need a big resistor to limit current, you find the value by adding load current to voltage regulator current,for the OA2 that's at least 5mA. That's a lot of heat inside your chassis.
Apart from them looking nice VR valves on their own do a brilliant job of regulation, there's no fold back. As part of a regulated supply though they're better.
0A2 and other VR (voltage regulator) tubes can be used to help control HT surge voltage...off the rectifier, the series dropping resistor and the VR tubes can limit HT surge voltage until the other tubes warm up and draw current. This works nice with solid state rectifiers or the 5Y3 direct heated types which conduct immediately on application of voltage. Helps save the filter capacitors from excess HT during warm up.
My question would not be how much current the supply can furnish but how much current is actually being drawn?
The 0A2 can only work with continuous currents between 5mA and 30mA while the 0D3 works with 5mA up to a maximum of 40mA.
My experience with VR tubes is very limited and I've never used them in series. My understanding is that series operation can be used to increase the regulated voltage but that the acceptable range of current does not increase.
Someone please correct me if I'm wrong on this.
If it stays the same, you're out of luck if you need more than 40mA.
I'm not familiar with the current drawn by the Aikido but as long as the current is within bounds, I'd opt for the 0D3 just because I prefer octals and I would think it would look better since the 6SN7s are also octals.
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Use a MOSFET source follower with the VR tubes hooked up to the gate with a gate stopper resistor. The VR tubes can be run at minimal current, and you'll have all the current you'll need for the preamp. 0D3s light up much nicer than 0A2s, if that's your thing.
My favorite visually is the OA3. Two in series here on a preamp I built.
Here is the same pre with OC3s
Here is the same pre with OC3s
FlaCharlie... one can connect VR tubes such as the OD3 in series to obtain the desired regulated voltage with 100 k equalizing resistors across each VR tube, and a suitable series dropping resistor from unregulated DC. The regulated current range remains the same regardless of the VR tubes in series. If you want to stick with tube regulator circuits but require more current, look in the UTC transformer catalog for circuits. They use a VR tube voltage reference but the pass tube is a 6L6 or 6AS7 type...
This is how I did it. I did not add the resistors as I wasn't smart enough to do so. Seems to work OK so far.
WntrMute2... that circuit you posted will work. The equalizing resistors become more "useful" as the VR tubes age. BTW I know Dr. Greg Latta at Frostburg University. He teaches physics there and really knows his material. He also enjoys classical music and recording...and plays the hammered dulcimer...
Just one of the tubes. Helps the other tube strike first, doing a so-so job of limiting overall maximum voltage prior to both being at steady state voltage.
No, assuming they are the same tube.
If different voltages, you could be particular and choose which one you want to strike first. Kind of no big deal.
If different voltages, you could be particular and choose which one you want to strike first. Kind of no big deal.
