A while back, in my search for interesting oddball tubes, I came across the 5A6 which is a directly heated beam tube with a 9 pin mini base. I've attached the data sheet.
A search here and elsewhere came up mostly empty. There were a couple of references to it being used as a preamp tube, wired in triode, where it has a mu of 6.8. Links to a Japanese schematic were dead and not available via Wayback. If anyone has them saved, please post them.
It's apparently designed as an output tube for RF applications. I'm wondering if it can also be used as an audio output tube in beam pentode mode. If so, what load would work and what operating points would you recommend? It seems to run at low (150v) plate voltage.
Anyone know of any other directly heated 9 pin minis? This is the only one I've found.
A search here and elsewhere came up mostly empty. There were a couple of references to it being used as a preamp tube, wired in triode, where it has a mu of 6.8. Links to a Japanese schematic were dead and not available via Wayback. If anyone has them saved, please post them.
It's apparently designed as an output tube for RF applications. I'm wondering if it can also be used as an audio output tube in beam pentode mode. If so, what load would work and what operating points would you recommend? It seems to run at low (150v) plate voltage.
Anyone know of any other directly heated 9 pin minis? This is the only one I've found.
Perhaps for an headphone amp, little gain and 1,5W out (Vb=150V Ia=30mA Ra=3k3 Vg1=-9V Vg2=150V)
Mona
Mona
The DC80/1E3 is a directly heated 9 pin (Noval) triode: DC80 Radiomuseum
The 2DF4 is a directly heated 9 pin (Noval) pentode: 2DF4 Radiomuseum
The 2DF4 is a directly heated 9 pin (Noval) pentode: 2DF4 Radiomuseum
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My interest in the 5A6 is mostly because there just don't seem to be many 9 pin mini tubes that are directly heated.
The 1E3 and 2DF4 look interesting although the 1E3 seems to be quite rare and the 2DF4 seems to be quite a bit more expensive than the 5A6.
I guess I was wondering if the 3w output mentioned in the 5A6 data for RF would equate to a 3w output when used for audio. I guess not, which is probably why the only mention I'd seen of it being used was as a preamp tube wired in triode.
Since the "inverted SET" that I built recently turned out so well,
https://www.audiokarma.org/forums/index.php?threads/the-nuance-my-inverted-set-diy-project.990205/
maybe I'll try a simplified 9 pin mini version using a triode wired 5A6 on the input and a 6BQ5 for the output. I've also considered doing a 7 pin mini version using the 3A5 for the input and a 6AQ5 for the output.
I don't use headphones, so 1w or less doesn't appeal to me. The little Magnavox SE amp that I modded to use 12BH7 outputs sounds great but that's probably as low as I want to go in terms of power output.
https://www.audiokarma.org/forums/i...0-or-8600-conversion-to-12bh7-outputs.824135/
The 1E3 and 2DF4 look interesting although the 1E3 seems to be quite rare and the 2DF4 seems to be quite a bit more expensive than the 5A6.
I guess I was wondering if the 3w output mentioned in the 5A6 data for RF would equate to a 3w output when used for audio. I guess not, which is probably why the only mention I'd seen of it being used was as a preamp tube wired in triode.
Since the "inverted SET" that I built recently turned out so well,
https://www.audiokarma.org/forums/index.php?threads/the-nuance-my-inverted-set-diy-project.990205/
maybe I'll try a simplified 9 pin mini version using a triode wired 5A6 on the input and a 6BQ5 for the output. I've also considered doing a 7 pin mini version using the 3A5 for the input and a 6AQ5 for the output.
I don't use headphones, so 1w or less doesn't appeal to me. The little Magnavox SE amp that I modded to use 12BH7 outputs sounds great but that's probably as low as I want to go in terms of power output.
https://www.audiokarma.org/forums/i...0-or-8600-conversion-to-12bh7-outputs.824135/
I've tested 6 of them for my friends, but since he wanted to use them in a push-pull headphone amplifier. I only scanned the triode connected curves and 43% 190V Ultra Linear connected curves of them (his OPT has 43% UL taps, and 190V B+ seems to be OK according to the curves).
Hope these could be helpful.
Triode Connected
Plate Current in Ultra Linear 43% and 190V B+
Grid2 Current in Ultra Linear 43% and 190V B+
Hope these could be helpful.
Triode Connected
Plate Current in Ultra Linear 43% and 190V B+
Grid2 Current in Ultra Linear 43% and 190V B+
The 5A6 looks like it was designed for field use from a 6V storage battery,
The operator could adjust the filament in an environment where his battery is continuously sagging.
The US automotive fleet was still 6V in 1949. And SS was still years away for 70 MHz TX.
I once owned a couple of small MG sets, one was a PE103A as I recall. Built by Electrolux in the US.
It could be powered by either 6 or 12V. The HV was 500V, 160 mA. Enough for a fairly powerful TX.
An interesting device, the rotating armature was wound with both LV & HV windings, commutators on each end.
And had a full set of RF filters. All in a completely sealed, weather proof package,
Some people called this a 'Genomotor'. Many were in service in WW2 with the military.
I gave it away many years ago to a antique radio club.
The operator could adjust the filament in an environment where his battery is continuously sagging.
The US automotive fleet was still 6V in 1949. And SS was still years away for 70 MHz TX.
I once owned a couple of small MG sets, one was a PE103A as I recall. Built by Electrolux in the US.
It could be powered by either 6 or 12V. The HV was 500V, 160 mA. Enough for a fairly powerful TX.
An interesting device, the rotating armature was wound with both LV & HV windings, commutators on each end.
And had a full set of RF filters. All in a completely sealed, weather proof package,
Some people called this a 'Genomotor'. Many were in service in WW2 with the military.
I gave it away many years ago to a antique radio club.