metasonix rk7: thyratron vco price : $750.00

the rk7 is an 8hp eurorack version of our legendary tm-3/s-1000/r-55 vco circuit. the entire circuit is based on two tubes: a 5696 thyratron and a 5702 subminiature pentode, both of which are military surplus tubes used in avionics. the 5696s are still available but getting scarce, and they require a higher plate voltage than our other euro modules. like the r-55, the rk7 has a pentode clipping stage which provides voltage control over the gain and clipping level. 5702 subminiature pentodes have always been rare and little used outside military equipment.

the rk7 is profoundly weird and erratic. don't expect it to be perfect - it's far from that. we've been making products with them for 20 years and still can't figure out the whole situation. apart from the early trautonium in the 1930s, no one ever used thyratrons as music vcos before.

the pitch and vca cv inputs accept -10v to +10v with minimum 50k ohm input impedances. the pitch cv input is limited to +/-10v range and is hz/volt only. the usable pitch control cv is roughly 0-4 volts, depending on the setting of the span trimpot, while the vco itself only produces slightly more than 2 octaves from cv control. the vca cv input uses bipolar cvs (such as lfos) or audio signals, and cannot be damaged by over-voltage.