Hi Jaap, yes, you could certainly try it, though whether you need it very much will depend on the type of output valve.
But with all closed-loop systems, please take care to see that frequency compensation is correctly applied.
I imagine that you are using a high-performance, wide-bandwidth transformer - it will be needed!
Place the compensation cap in parallel with the output resistor. Take care that ferrite-beads are present on all the susceptible nodes (anode, PNP base & collector), and that they are lower-frequency types - losses in the 500kHz-10MHz range are needed for these.
screen the feedback wire, and keep all of the circuit small.
But with all closed-loop systems, please take care to see that frequency compensation is correctly applied.
I imagine that you are using a high-performance, wide-bandwidth transformer - it will be needed!
Place the compensation cap in parallel with the output resistor. Take care that ferrite-beads are present on all the susceptible nodes (anode, PNP base & collector), and that they are lower-frequency types - losses in the 500kHz-10MHz range are needed for these.
screen the feedback wire, and keep all of the circuit small.
Reviving an all thread after doing further experiments with this great driver:
6?5? Shunt Cascode Driver | Bartola Valves
Hope you find this useful
Cheers
Ale
6?5? Shunt Cascode Driver | Bartola Valves
Hope you find this useful
Cheers
Ale
So this is what is arousing your curiosity.......?
Driving a 300b is one of the basic challenges in SE amp theory and practice, and has been for many years!
Driving a 300b is one of the basic challenges in SE amp theory and practice, and has been for many years!
Indeed. Well, I've been experimenting with different drivers as you know. Not needed for a 4P1L stage, but if you look at 300B, 814, 813, GM-70 and other transmitting valves, is key to get it right.
Hello,
Is there any conclusion to this thread? Or are you all just ******* in the wind?
RC in VT, USA
Is there any conclusion to this thread? Or are you all just ******* in the wind?
RC in VT, USA
This is a long inactive thread, I think you can draw all of the conclusions needed from the fact that the last post was > 4 years ago.
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Well........ I still have the parts set aside, a 2A3 which was to be driven by a 12AX7. It’s got to be built, can’t just leave a new JJ 2A3 and Sowter OPT sit forever. I have a dozen 3A5’s so the experiments are only waiting for me. Ah, now I see the problem :-D
After ten years absense while doing other fun activities not involving electronics, I stumbled upon this thread and had to give it a go. This concept seems to work OK in the simmed world with parallelled 3A5 as driver, Had to spend half an evening brushing up LTSpice commandos.
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Hi Andy,
Just a small try to see if I still had some knowledge left. Went through the neglected electronic workshop, to sort out things as we a have bought a new house and found this stereo 6B4G PP chassis with wired cathode circuits and a handfull of 3A5´s, but without drivers. Next sim will be a PP version.
Just a small try to see if I still had some knowledge left. Went through the neglected electronic workshop, to sort out things as we a have bought a new house and found this stereo 6B4G PP chassis with wired cathode circuits and a handfull of 3A5´s, but without drivers. Next sim will be a PP version.
Welcome back revintage 🙂
In #168 schematic what happens if the 3a5 filament goes kaput!!?
Does the 2a3 remain in a safe zone ?
Can I build it IOW
In #168 schematic what happens if the 3a5 filament goes kaput!!?
Does the 2a3 remain in a safe zone ?
Can I build it IOW
Thanks pl802!
Hadn´t given safety a thought😛.
Can absolutely be built, but I would go for 6B4G with its lower heater current. Probaly needs some tweaking.
Senstivity is on the low side with just over 2V for 2W out.
Anyway, I pulled the 3A5 and got 105mA, 101V, 10,3W over the output tube, so it should cope. Also shorted the driver anode to ground and got 36mA, 350V, 12,5W.
https://shop.ehx.com/catalog/tubes-specs/6b4g-sovtek.pdf
https://soderquist.se/3A52A3choke.asc
Hadn´t given safety a thought😛.
Can absolutely be built, but I would go for 6B4G with its lower heater current. Probaly needs some tweaking.
Senstivity is on the low side with just over 2V for 2W out.
Anyway, I pulled the 3A5 and got 105mA, 101V, 10,3W over the output tube, so it should cope. Also shorted the driver anode to ground and got 36mA, 350V, 12,5W.
https://shop.ehx.com/catalog/tubes-specs/6b4g-sovtek.pdf
https://soderquist.se/3A52A3choke.asc
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Another idea for a 3A5-2A3 SE using a small mains toroid as OPT. This is a mod of my SETOR that has been playing for many years with 6L6 instead of the NMOS and 6C45 as driver.
I have uploaded it to my website. Have tried downloading and then opened it, no problem. I use the newest version XVII. As I said earlier, mail me!
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