  We present a novel compact dual-comb source based on a monolithic optical
crystalline MgF$_2$ multi-resonator stack. The coherent soliton combs generated
in two microresonators of the stack with the repetition rate of 12.1 GHz and
difference of 1.62 MHz provided after heterodyning a 300 MHz wide
radio-frequency comb. Analogous system can be used for dual-comb spectroscopy,
coherent LIDAR applications and massively parallel optical communications.
