24/96 digitalization - can it be audible
Reply #7 – 2011-06-19 16:17:53
Thanks everyone for you comments. And sorry for my slow response, I have to discuss the details with the other test organizer, and being on different continents and in different time zones, we need time for this.are you sure that the Tascam had exact unity gain? The difference was <0.2 dB.it would be nice to see RMAA results of it. Wouldn't it require using measurement equipment that has better specs than the Tascam ?Levels set so clipping might have happened (like when the stylus hit the record)? The preamplifier was muted before lowering the stylus and unmuted afterwards. It's a slow, ~2s mute/unmute. Placing the stylus and muting/unmuting was done by a person unaware whether the current trial was A or D.Sometimes with equipment like that "monitor mode" is meant for monitoring, not an output used for production, and is not up to the full specs. We used the regular Analog Out RCA outputs. As far as we know, the procedure is identical to normal "production" recording except that there is no recording.What sort of time delay is there in the A/D/A process? Could there be some crosstalk or bleed through that would give a subtle pre-echo of the original analog? We'll look into the possibility of measuring this delay. On the other hand, Tascam specs say that crosstalk is <-97 dB At this point we have to admit that we have found a potential confound, although it might be irrelevant. We ensured that the levels were below clipping by observing Tascam's clipping indicators during pre-test runs. Everything seemed fine. But we also recorded the test music using the same configuration and settings, and there was tiny amount of slight clipping in the recorded file, namely 21/98 samples in L/R channels, for a total of >17 million samples in each channel. We are not sure if this can be audible/significant, but it is a methodological flaw, and we'll try to find a way of avoiding it, should we re-do the test, or do similar tests.