We Have some Reference! Managed to pull ~4.5Mhz on VICHY VC99. The signal was fed directly to VC99(not terminated), while in audible range it was also powering 64Ω headphones (32Ω+32Ω connected in series)
TODO: adding amplifier and digital pots for AREF and amplified signal attenuation, phase shifting. This will be remotely controllable & programmable DDS.