B.M.C. Belt Drive Transport
Superlink & SPDIF Interfaces
For transmitting digital audio signals besides the established SPDIF-compatible interfaces (AES/EBU 110 Ohm, coaxial 75 Ohm and optical Toslink) there is the exceptional and consequent “Superlink”. Unlike SPDIF transmission the different digital audio signals are not merged to one single signal stream and decoded to separate signals again after being received by the DAC.
SPDIF surely makes sense from the commercial point of view, but Superlink is the solution without compromise, which requires 4 times of interconnection cables but skips any coding process. Left/right-clock, bit-clock, digital audio music data are transmistted from the CD-transport to the DAC while the master-clock is generated inside the DAC and sent to the CD-transport. The transmission is done with 4 x 75-Ohm BNC cables with impedance matching. Superlink results in a more intense link to the music, wider and more realistic sound-stage, more details and beautiful sound colours.
Any digital or analogue circuit has a sonic dependency on the power supply. Due to the fact that different power supplies have different influence on the music reproduction B.M.C.'s CD transport uses an advanced switching power supply, with active primary voltage filtering and separate transformers for display, motor, logic and audio circuitry on digital and analogue domain. Additionally there is complex voltage stabilisation separately in front of each functional group.
Optional Upgrade to a CD Player
By adding the digital-to-analogue converter module the belt drive CD transport can turn into a complete CD player with analogue output.
The digital signal performance is optimised by a clock synchronisation circuit right in front of the DAC-Chips. All digital signals are re-timed to the local master clock and thus the point of lowest jitter is at the DAC-Chip where the analogue music signal is made. The conversion is made by two 24-Bit / 192kHz TI/Burr-Brown PCM1792 chips with current output.
The output current is filtered and converted in to an output voltage by discrete, fully balanced I/V converters, which operate feedback free. Thanks to the special “Current Injection” circuitry a maximum of sound quality is preserved, which is stabilised with the unmatched “LEF” driver circuit keeping all sonic details.
Originally those circuits were designed to put focus on the sound quality and leave the measurement specifications second, but the present standard is on a level that leaves no need for such choice: Both are on top level and the sound is class of their own.
The combination of a belt driven CD transport (belt-drive, precision bearing, CD stabiliser with flywheel effect) and consequent digital signal interconnection, as well as an optional DAC with advantageous technology concludes in a musical performance never revealing its digital origin.