Russian rod pentode circuits

[Murphyv310]

Hi
As Michael says Bulgaria and Ukraine, also Russia but less these days.
They are wonderful little valves to play with and extremely versatile.
Last year I made a Band 1 TV modulator to run my 405 line TVs using these valves with great success. I've made pantry transmitters with only five external components that has the often raved about minimod had for breakfast Lunch and dinner.
Get some and enjoy yourself.... I certainly have.
Incidentally the 1j24p will make a 15 watt transmitter for CW or AM and last many hundreds of hours, I paralleled two and ran 40 watts, any more will red plate them but funnily enough they seem to survive this hard treatment very well.

[Jez]

So is there actually a 1ж24п or this a typo and 1ж24б what was meant? I see references to both, plus Mike saying to avoid the 1ж24п as "it's a monster", but elsewhere I see someone admitting it was a typo when they wrote of 1ж24п. I can't find a datasheet etc for 1ж24п and only maybe half a dozen mentions of it on google, all in Russian.

To be clear, my interests are for mains powering them, including the heaters, and size, power consumption etc is N/A.

Whilst I would have fun building superregens with them etc and may use batteries for portability there, what I really want to experiment with is whether or not the somewhat odd characteristics of the rod pentodes could be put to use for hi fi pre amplifiers, microphone amps and phono stages etc. ie may they, under the right conditions, give markedly less distortion and or lower noise than conventional valves.

[Murphyv310]

Hi
I use a 1j24b in my 1955 Pye BB record player as a preamp from my ceramic Sonotone cartridge, it has RIAA equalisation. Been in the record player for around 6 years now on veroboard mounted on the cabinet floor, filaments taken from the 6.3v heater supply suitably rectified, smoothed and regulated. HT taken from the HT of the main amp and again smoothed and dropped to 60v. Works perfectly.

[Mike Watterson]

So is there actually a 1ж24п or this a typo and 1ж24б what was meant? I see references to both, plus Mike saying to avoid the  1ж24п as "it's a monster", but elsewhere I see someone admitting it was a typo when they wrote of 1ж24п. I can't find a datasheet etc for 1ж24п and only maybe half a dozen mentions of it on google, all in Russian.

To be clear, my interests are for mains powering them, including the heaters, and size, power consumption etc is N/A.

…
what I really want to experiment with is whether or not the somewhat odd characteristics of the rod pentodes could be put to use for hi fi pre amplifiers, microphone amps and phono stages etc. ie may they, under the right conditions, give markedly less distortion and or lower noise than conventional valves.

Yes, you can use a 1.2V DC supply and multiple HT rails from 45V to 200V depending on model from the mains.
All amps need some negative feedback to be linear. The Rod pentodes have no "real" grids, being electrostatically focused beams, so very very low noise. They are inherently sharp cut-off and fairly linear, so pentode designs like for EF80 or EL84 will work. The g2 can be tied to anode for a more triode like performance, but unlike real pentodes the g3 must be tied to 0V, f- or f+ or some LT voltage. Note that Beam Tetrodes and Kinkless Tetrode are more like pentodes, and really the g3 "beam plates" is electrostatic rather traditional grid like an EF50 or EF80.

1ж24n is Cyrillic. Transliterates to 1j24p. The ж is also transliterated to sh and zh as well as j.
But a typo. Should be 1p24b, or 1П24Б
My mistake earlier. It's been a few years!
Data Radiomuseum 1p24b-v
The suffixes are variations of robustness.

Really unless you want batteries an EL8x is better choice than a 1p24b.

And for mains powered audio the EF86 for preamps. EF80 (common as muck) everywhere else. You can maybe get 500mW+ audio on an EF80, and you can use them as triodes, or maybe 2W class B push-pull.

Another good mains valve is ECH81 / ECH83 (often the same valve marked differently). It, ECC82, EF89 and some others will work at 11V to 14V HT. While the ECH81/ECH83 has a common cathode it can be used as a separate pentode (just fixed biased Hexode) and triode. Thus an ECH81 can be Pentode preamp and triode phase splitter. It also can do moderate listenable power direct.

There is almost no point to using the Rod Pentodes on mains only, apart from the monster 1p24b, but many mains valves make more sense. The 1p family was mostly used in short life proximity fuse and earlier versions in some early satellites inc actual sputnik. I have a bunch of 1p24b, but only for testing. I think pointless. I have many of most Rod Pentodes. I also think the 1j37b is only of historic interest. A PIN diode is a better variable gain (and an 1N4007 works at HF!), and plenty of better mixers.

Hence I only bought more 1j24p and 1j29b. The 1p2x other than 1p24b are just older models.
The 1j17b is very old, replaced by 1j18p, replaced by 1j24b.

Main Radio Museum thread and list of known types with links to data

See also https://www.radiomuseum.org/forum/rod_tu..._1960.html Link to translated PDF

I got a couple of 1j42a to test, but can't imagine making anything with them.

The last one to be found AFAIK is the EM10, electrometer valve. Seller is in Ukraine.
Seller also has miniaturised versions of the 6.3V indirect filament valves close to Rod Pentode appearance. Also there are EMxx series miniature Electrometer valves that are not Rod Pentodes. I have a Russian schematic of an Electrometer maybe using the 1j42a and 1j24b, not sure.

I also have the USA/UK sub-miniature vavles used in military, hearing aids and some japanese pocket radios (unless earphone only, they used like a DL91 or similar B7G for audio out). They are inferior to the rod pentodes, though there is a triode-pentode mixer. I have some NOS nuvistors which were a crazy idea. Only widespread consumer use was VHF tuner-heads in mains equipment. Too expensive. Quickly replaced by VHF Germanium and then Silicon.

[Jez]

Hmm I think we disagree on a few things! Nuvistors are virtually the holy grail of valves for a start! Absolutely superb for many of my applications. getting the sockets is an issue though. I design hi fi equipment as the day job, using valves as well as solid state BTW, so I'm familiar with the likes of the EF86. A pretty useless valve actually. Low noise compared to what? other very noisy pentodes? I've never found a use for them in audio!

I reckon 1ж24б and 1ж29б -в then plus there's a few others I've been meaning to get for a while such as some 6с17к-в and 6ж52п so I'll have to search for a store that has all and can combine the postage.

Prices seem to vary considerably and delivery time up to 3 months! all looks a little dodgy....

Добрий вечір

[Murphyv310]

Hi.
Michael...... Did you ever get a 1J42A to oscillate by space charge?

The 1J42A is a fantastic valve, If you have any I'd happily give you decent money for them, I've used them in many projects and their higher rated cousin (37), in fact my first band 1 modulator used the 1j42a then replaced with a 1j37b for higher RF output, we did differ though in the way I use the valve, perhaps not highly efficient but nonetheless does the job.
The 1j42a is one of the easiest valves to oscillate and I've even coaxed it to work up to 100Mhz, the trick is to run it on starvation mode, 1.5v HT and 0.9v filaments and it will oscillate at these frequencies. I just wish there were more around. Vilk in Ukraine has them on his list for me but due to circumstances I doubt he'll be able to help.

[Murphyv310]

Hi.
I'm sure Kalee 20 built a superhet radio using only rod pentode valves.

[Murphyv310]

I design hi fi equipment as the day job, using valves as well as solid state BTW, so I'm familiar with the likes of the EF86. A pretty useless valve actually. Low noise compared to what? other very noisy pentodes? I've never found a use for them in audio!

Hi.
Well that's a statement and a half! So what would you consider a low noise valve? The EF37A was considered a low noise valve but what is the benchmark you are using to make comparisons?

[Kalee20]

Any mixer can be implemented as plug in replacement using 2x 1j24b, one as a triode oscillator and that can direct drive g2 of the RF in/Mixer. Less LO leakage than DK91, DK96, DK92 and 1L6.

Interesting! I made a superhet using Russian rod pentodes in 2021 (rather a lot, 13 in fact!). The frequency changer uses a 1j24b as oscillator, driving g3 of two 1j24b's in antiphase, while RF is applied to both g1's together. IF is available at the anodes, this driving a centre-tapped-primary first IFT.

I found that bias on g3 was fairly critical for best results - they're at about -10V (without consulting notes) and the LO swings g3's from -20V to 0V.

For what it's worth, the other ten rod pentodes are: Two IF stages; infinite impedance detector (yes! With directly heated, grounded filament); AF amplifier; phase inverter; push-pull output stage (this using 2 x 1p24b's in ultra-linear, giving 2W).

That brings up to ten... the last three then are a further IF amplifier, driving a leaky-grid detector, with anode bypassed to ground for everything from a couple of Hz upwards... the mean DC level here is used as AVC control voltage. The last pentode is a DC amplifier and inverter (with voltage delay), and the amplified control voltage is applied to g2's of the frequency changer and g2's and g3's of the IF amplifiers, appropriately level-shifted.

LT is regulated at 1.15V; HT at 120V and there's a -80V rail which I needed for the infinite impedance detector, and also potted-down biases the output stage and the AVC line. They're all derived from a heavily-screened flyback converter running from a 12V battery.

It works well (it's playing right now)!

[Jez]

I design hi fi equipment as the day job, using valves as well as solid state BTW, so I'm familiar with the likes of the EF86. A pretty useless valve actually. Low noise compared to what? other very noisy pentodes? I've never found a use for them in audio!

Hi.
Well that's a statement and a half! So what would you consider a low noise valve? The EF37A was considered a low noise valve but what is the benchmark you are using to make comparisons?

All pentodes are useless as low level low noise valves. That is kinda the point. An ECC88 in cascode will give at least as much gain and way lower noise. A decent ECC83 is pretty low noise and no slouch mu wise. Most low level valve circuitry back in the day was pretty rubbish really so I guess they got away with the EF86 and at least the spiral filament helped with hum. They didn't appear to know that resistors generate noise for a start and you will see things like 1M in feedback or EQ networks or shunt feedback RIAA with a resistor of 22K -100K ish in series with the magnetic cartridge