The DAC-1 is the inital component which will give way to the Music Link series... once Philips will have had its own SC-22 export version, and added the Music Link tag along the way.
The SC-23, shown here below, is a later version, visually slightly redesigned (knobs/switches/"blue star" surrounds) and put in the vented enclosure of the DMA-1 / MA-23 power amp ; otherwise equivalent but for improved specs separating it from the two original versions.
All three versions make for a line-level preamp with super-permalloy core transformer-balanced outputs allowing phase+ / phase- amplification, one main toroidal transformer, an old ALPS RK50 2-gang pot (aka "Black Beauty"), Nichicon Muse caps, 70µ copper glass epoxy PCBs, a diecast chassis on which copper-plated separations actually hold the hardware, 24K gold-plated terminals, 8mm front aluminium slab, 4mm aluminium top and solid aluminium knobs and switches - all non-magnetic.
The circuit design was mainly inherited from the DLT-1 line transformer (upped and remade with the post-Music Link LT-1) : all input signals go through a pair of LPF to block everything digital sources may leak through analogue circuits - see the schematic below.
The SC-23, however, has a much wider frequency response - Philips/Marantz may have decided to change their LPF slope or type for more high-end transparency...
As the dwindling of the suggested pricelist suggests, from 160k¥ to 120k¥ in three steps, Marantz obviously found the DAC-1 / SC-22 / SC-23 difficult to sell...
A real EU SC-22 here ; a JP SC22 here ; nudies of an EU SC-23 here ; nudies of a JP SC-23 and two DMA-1s here.