Introduction

My Minidisc deck until recently, a Sony JE-520, along with other similar Sony decks has a digital pass-through option where by pressing record with no disc in the machine digital input is sent directly to the digital output. The implication is that this digital output is unaltered as it passes through.

Observation

I previously used a hi-fi DAC which supported HDCD which encodes extra information on the CD. Checking whether this information is preserved served as a simple but effective way of testing for accurate transfer; if the HDCD light comes on for HDCD recordings then the information transfer is good, if not something is up.

I noticed with the Minidisc deck in pass-through mode ("- DA" on the display) the HDCD information was not preserved. However, if you insert a disc and put the deck into record or record-pause mode the information is preserved.

I suspected that with the disc in the deck the bit-stream was being passed unaltered. However, more recently I was using the deck as an optical repeater whilst conducting some sound card tests. I found that even with the disc in the drive the bit-stream did not exactly match the original.