Zerosum Inertia - 6550-99 Tube Oscillator
Power draw:
50 mA +15
50 mA -15
1.8 AMPS +5 on power up for the 2050 thyratron.
Top switch: mode behavior.
When mode behavior switch is down,
Top knob adjust clipping amount of variable waveshape from saw to square to rectangle to near silent narrow pulse width. Full clockwise could result in inaudible 100% pulse silence.
Recommended to start with this knob in 12 o clock position.
When the mode behavior switch is up this knob functions as a pitch control for the 5823.
Left knob adjusts the pitch control of the 2050w oscillator.
Left CV in is unattenuated HZ/V input. You are encouraged to insert audio rate oscillators into here. But you can also feed HZ/V sequence/CV signals into here for interesting experiments.
There is no Exponential V/oct chip onboard. You are inserting control voltage into the 2050W tube.
Right knob is an active attenuator for the CV input below it.
Center knob adjust the output volume level.
Tubes used in the 6550-99 VCO:
The 6550-99 uses two extremely special gas-filled tubes, never seen in audio equipment before. Their unique characteristics result in the 6550-99 sounding like no other electronic-music device on the market, today or ever.
2050
The 2050 xenon-filled tetrode thyratron was introduced by RCA in 1939. (A thyratron is a gas-filled tube used for on-off switching applications, not for amplifying signals.) It was designed with low grid leakage and high sensitivity, specifically so it could be used to switch on a relay or other device when driven directly with a vacuum phototube. This high sensitivity makes it an excellent tube for voltage-controlled oscillator use.
Among the first uses of the 2050 were during the war, as a noise generator in the US Navy 60140 sonar jammer, and to fire the overmodulation lamp in the General Radio 1931 AM modulation monitor. Apart from other assorted industrial and commercial applications, 2050s are often seen controlling relays and selector solenoids in jukeboxes from the 1940-1955 era, notably to pulse the "stepper selector" in several models of jukeboxes made by Seeburg during this period. Especially the legendary 222 and DS100 series, the world's first stereophonic jukeboxes.
The 2050 enjoyed a very long commercial life, from before WWII until the 1980s, especially in military equipment. In fact, a special, very rare ruggedized "W" version with a silicone-filled melamine "cup" base was manufactured for use in airborne electronics. Many were used in the complex electronics of the B-52 bomber. Other variations of the 2050 have existed, including the lower-rated 2051, the rare 502A, and the even rarer 1657 and 1661, specially made for a single industrial customer.
5823
Few tubes are more rare or obscure than the 5823 cold-cathode trigger triode. (Unlike the hot-cathode 2050 thyratron, cold-cathode tubes did not require a heater power supply and were simpler to use, but were less sensitive to trigger signals than hot-cathode types.) Introduced by Philips in 1949, originally under the number Z900T. It was found in "industrial timers and IBM business machines" of the 1940s.
Perhaps the largest and most notorious application for the 5823 was as the "reset" device in synchronized wall clocks manufactured by IBM and Simplex Corp. from the late 1940s until the 1960s. Such clocks were often seen in public schools, hospitals and government buildings. The clock mechanisms were typical synchronous-motor designs running from 120 volts AC, except each one also contained a 5823 tube and a reset solenoid. All the clocks in the system were fed a high-voltage reset pulse every hour or day, which fired the 5823s and forcibly reset the clock hands, thus insuring all the clocks read the same time consistently. The cold-cathode 5823 didn't need heater power, so it minimized the amount of wiring that needed to be installed for all the clocks in a building. Power consumption was also minimized. The 5823 was rated for "45,000,000 firings" of lifetime at the full 25 mA current.
When connected as an audio noise source with the gate electrode positively biased, the 5823 produces a distinctive "whining" noise signal. It was not designed for this purpose, but does it extremely well because of its cold-cathode construction. Only Zerosum Inertia synthesizer products use the 5823 as a noise source. Plus, the output signal of the 2050 thyratron in the 6550-99 is fed to the 5823, causing strange interactions and instability.
