Description
The converter is a two board stack that fits into one of the option slots in the preamp. On the first board, all incoming digital audio is upsampled to 3.125MHz/32 bits and converted to noise shaped PWM. On the other board are two mono DACs, in which a discrete 32- stage FIR DAC and a single-stage 4th order filtering I/V converter, convert the PWM into analogue with a breathtaking 130dB SNR.
This is near the theoretical limit for 24-bit files and far beyond that of even quad-speed DSD. Uniquely, distortion remains below the noise floor even for full scale signals. A quick look at current and historic trends of high-end IC’s indicates that for the foreseeable future this kind of performance will remain unavailable to manufacturers forced to rely on the same ‘chip du jour” that also powers their competitors’ products.
Even by today’s exacting standards, extraordinary care has been taken to deal with jitter. Mola Mola’s DAC uses a home-grown asynchronous upsampling algorithm whose input frequency measurement slows down rapidly until after a few seconds of lock, the frequency ratio measurement is frozen. Frequency stability is then wholly determined by the internal clock, a laboratory grade 100MHz SC-cut oscillator. This is effectively an atomic clock sans the physics package (which contributes nothing to spectral purity but quite a lot to cost).
