Tube VCA 1Ж24Б









This design is inspired by Ken Stone's Tube VCA and based on 60s-70s soviet tube 1Ж24Б. (I've contacted with Ken and got his blessing. Hi specified to write 'inspired by' since it's modified unofficial release. Thanks Ken for help and sharing!)
I considered the mods described at e-m forum. Thanks to PrimateSynthesis for that great work .

The device has feedback loop which is normaled to IN2 jack, so IN2 pot controls feedback amount when nothing feed into IN2 jack and feedback switch is on. When jack feed into IN2, IN2/FEEDB pot controls IN2 level. Distortion/clean switch controls two modes with more or less distortion which amount can be trimmed with trimpots through holes at panel. Drive/IN1 pot controls IN1 level. GAIN pot controls gain offset. CV pot controls gain CV level.


Power consumption: V+ 12mA, V- 25mA.


PCB - 2mm thickness, gold platted, black mask. $25


Two panels - 10HP front & back. Anodized alu, black print. $25


Tube 1Ж24Б. $5 (I don't sell tubes without boards)


SMD parts + soldering. $10 (Who order SMD soldering please note if 15V version in payment comments, I make 12V by default)


Shipping per set: $5 - only board, $8 - board+panels.


TOTAL for complete set with shipping: $73


Paypal: info(at)


Assembled module $260 + $10 shipping.


Thread at MuffWiggler forum







Demo from ddoyen@Muff :














PCB top.

PCB bottom.


Front panel.

Back panel.








Parts not included in Mouser shopping carts:


4 potentiometers
4 knobs

Where to buy?


1. Thonk:


2. Erthenvar:


3. Smallbear:


4. Tayda:




I included into Mouser shopping cart 8 Kobiconn jacks. But they need to solder a leg for ground connection.
Better choise is Inline jacks:


1. Thonk:


2. Erthenvar:



Some interesting facts about soviet subminiature rod tube 1Ж24Б.



Rod radio tubes, where the control electron flow is not using grids, blocks the electron flow, as in conventional tubes, and rods using electrostatic lenses that change the intensity and focus the electron beam - this is a brilliant Soviet development.


They were developed in the USSR by V. N. Avdeev (1915-1972) in 1950 and meant the most significant change in design classic from the invention of electronic amplifying triodes in 1907.


They were created for battery powered military and space equipment. The mass distribution obtained in the early 60s. They have great reliability, shock and vibration, stability parameters, durability, comparable to the transistor, and the "lamp" radiation resistance makes them ideal amplifying device to operate in conditions of radiation and cosmic rays.


Very similar tube 1П24Б was on a radio transmitter on the first soviet sputnik in 1957. These tubes were into a radios on other manned and unmanned space vehicles, including the Vostok.
Sputnik transmitted "beep-beep"'s in two channels, 20 and 40 MHz, switching between two on-board transmitters having 1П24Б in output stages. All the initial animal and human test flights in Space used the Rod Pentodes.


As far as is known they were never used in Domestic Radio, but in Military and Aerospace including "man pack" radio sets. Production is believed to have ended as late as 1991 with one estimate of 200 Million made.


All soviet army radios used these tubes too.


Sputnik-1 Vostok-1 Vostok-1 spaceship
Vostok-1 controlpanel
Army radios





Assembling is pretty easy. Everyone can do it in a couple of hours.


Solder through-hole parts from low to high. First 10R resistors and diodes.

Then IC sockets.


Then caps, power socket and trimpots. From low to high.

A 'pillow' for tube. I made of foam from IC's packaging.

Isolate tubes legs with shrink tube. Blow hot air.


Install tube. Dot on tube => 1 pad on PCB.

Now clean bottom side. Look how clean it is obtained.

Mount spacers.


3. Mounting hardware.


Erthenvar jacks are too high in comparison to Kobicon. Cut these legs with pliers. We need to achieve 10mm between board and panel.

Kobiconn jacks need ground leg soldering. I use cutted resistor legs.

These spikes on pots need to be cuted.

Now insert all hardware but don't solder.

I use thin washers with Kobiconn jacks to achieve 10mm.

Now place a panel. Don't overtighten a nuts, just by hand.

Check everything is exactly precise.

Now solder. Be accurate, hard to clean now if to make dirty.

Now tight a nuts, not strong just a bit. Pots have a washers, so screwdriver doesn't scratch a panel.

Ready. Very nice and precise.

Insert IC's.

Now device is ready for backpanel mounting and power-up.


The device is ready!





1. Zero CV level.

Feed some signal into IN1. 1 kHz sine vawe from an oscillator will be fine. Set IN1 knob to max, set GAIN knob to 0.

Adjust 100K_CV trimpot on a board to hear nothing at out.

2. Distortion amount (trimpots on frontpanel).

Trim them on ear as you prefer.




(c) 2012 L-1 Synhesizer. E-mail: