I’ve now gotten confirmation that issues working at 44.1kHz are present on the original Ensoniq SCSI boards. At this point it seems that certain manufacturers, or possibly batches of IC’s are the source of the problem.

The SCSI board provides circuitry to isolate the signals to and from the DAC and ADC to eliminate noise and jitter. One of these signals is the 256Fs clock (256x sample rate) which is over 11 Mhz. Because of the design of the circuit, IC’s that are slightly out of spec won’t work properly. This isn’t the whole source of the problem, though. Some ASR-10’s exacerbate this situation, which I believe may be related to the revisions of the custom chips on the main board. So a SCSI board with an out-of-spec IC may work fine in one machine and have problems in another.

I have suggested a possible fix to a user who has this issue, if the fix is successful I’ll post it.