RK4 Filter / VCO
Post Modular
£430
The RK4 is the minimized version of our R-54 Supermodule, boiled down to a single 8hp module with a single vacuum tube. It uses a triode-pentode in a unique Wien-bridge circuit, to provide clean sine-wave oscillation. Using a Vactrol, the pitch of the RK4 is sweepable from less than 20 Hz to more than 2 kHz, continuously, via front-panel control or a CV input. By adjusting the waveshape/resonance control, the sinewave signal produced by the RK4 can be trimmed to less than 10% THD (depending on operating pitch) with NONE of the problems inherent in solid-state oscillators and sine waveshapers.
Post Modular's own words, read from their page.
Buy from POST MODULAR LIMITEDPOST MODULAR LIMITED is a UK retailer, not the maker. Price seen 2026-09-26. Not an affiliate link, we earn nothing from it.






