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.
Thanks Tom for making the SP-3 SCSI board. I was able to install without any issues. The analog jack board on the ASR-10 had to be isolated from the mounting tabs and screws, but once that was set all went fine. I’ve been using it for about a month now with no problems.
Tom, I also bought the SP-3 SCSI board but I’m having problems with any instrument using 44.1kHz effects. Changing the effects to 30kHz is a workaround. What are the latest developments with this issue?
Hi Ralph, your board is already on its way, but for everyone else: There are two IC’s on the board that need to be replaced, as they are marginal for the 44.1kHz sampling rate. FWIW this also affects the original Ensoniq SP-3 SCSI boards.
Hey Tom, just wanted to say the re-tooled SCSI board did the trick. It’s been working perfectly ever since I got it back. Wouldn’t want an ASR-10 without the SCSI2SD capability. Thanks again.