Mmmmm, yummy, R2R discrete mulitibt dacs, the best for Redbook,DXD PCM.
Just had a quick look at the specs, it seems they’ve used far higher spec’d R2R resistors for the Formula being 0.016% where the LaScala is 0.1% Also the output impedance of the buffer is a great low 10ohms, where the LaScala is 100ohms.
So go the Formula if it’s in your price range. There probably other advancements also.
Just found this also for the Formula
" The xHD update, This update has required significant optimization of code for the main FPGA of R2R ladder DAC which has improved sound quality."
Cheers George