Thick, glowing tubes and gas-filled bottles aren’t just for show here – they are the instrument. Every note you play travels through a fully tube-based audio path inspired by early 20th‑century radio circuits, while a modern ARM-core processor keeps the whole machine rock-solid and responsive. The result is a rare mix of old-world tone and present-day precision: duophonic lines that stay in tune, slam in the lows, and bloom with harmonics as you push the gain.
Apparatus by Eternal Engine is a desktop, duophonic analog synthesizer whose entire signal path runs on vacuum and gas-filled radio tubes, from the two independent quartz-stabilized thyratron oscillators through a second-order voltage-controlled lowpass filter capable of self-oscillation and overdrive, into a tube opto-compressor-style VCA and triode asymmetric overdrive. A velocity-sensitive ADSR, clock-syncable morphing LFO with sample & hold, and flexible portamento/legato modes invite expressive playing in both mono and duophonic modes. Hook up via CV/Gate for pitch, filter, and VCA control, process external audio through the tube path, and monitor levels on the analog VU meter, while the galvanically isolated PC connection and MIDI responses to pitch bend, mod wheel, and velocity keep it at home in a modern studio. Hand-assembled in limited quantities, it delivers classic tube character with the control and stability demanded by contemporary electronic musicians.
