On the switching routine between multiple ADC's-
This isn't the easily seen and heard channel muting done by Automix. It will be very, very subtle, and should be effectively inaudible except under extreme artificially manipulated scenarios. It specifically concerns the hand-off between the outputs of the lower-level ADC and the higher-level ADC. Since all ADC switching routines are proprietary, we don't know much about what artifacts might occur, when, and to what extent. This first came up in discussions about the Zoom F3, where presumably it was audible in some sound-design effects recordings pitched down from ultrasonic to audible range. Zoom issued a firmware update I think and I've not heard more discussion about it since. I don't think it's much of a practical concern, but it is a philosophical concern, and one that still bothers me about "32-bit recorders" in general. The manufactures moved the goal post - for convenience, away from perfection. Formerly the goal was analog-to-digital conversion that was as perfectly linear as possible across the entire audio spectrum within the dynamic range limits of the preamp and ADC - sort of an analog equivalent to digital "bit-perfect". In designs using switched ADCs this is philosophically no longer the case. Some distortion during the switch between ADCs is accepted as inevitable for the system to work as designed. The goal of absolute analog fidelity (input = output) is sacrificed for the convenience of not having to set levels. That trade off is a practical one that is worth it for most users in most cases, but it still bothers me philosophically, partly because what was formerly a clear, fundamental goal has been sacrificed for convenience. These new recording systems are no longer universal but can be problematic in special cases, like recording ultrasonic sounds and pitching them down for sound design work. The goal of convenience has eclipsed the goal of perfection. We are no longer aiming to design the most perfect audio recorders possible in terms of analog input = output. Not having to set levels has become more important.
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More importantly and OT, that calls into question the "truly analog perfect" nature of any recorder capable of 32-bit float which utilizes multiple switched ADCs. As long as digital inputs to the PR-4 bypass the ADCs and switching routine, which they should, digital inputs should be capable of being recorded in a "bit-perfect" way. But when recording an analog input, the switching between ADC's which serves to extend dynamic range capability without the users having to set gain must be handled very carefully, and can not be done absolutely perfectly. It will introduce some kind of distortion during the switch in some scenarios. How its done is handled differently by each manufacturer, cloaked in patent protections, and not discussed openly. Manufacturers have taken a "trust us it works" mentality.
As loose analogy, think of this sort of like modes of amplification. A "class A mode" amplifier does no switching between output devices and thus offers lower distortion than a class A/B amplifier. Does it matter? In some cases it does. We expect class A mode in microphone amplifiers, mic preamps and in other low current devices where low distortion is needed and inefficiency isn't problematic. And its not too bad for things like low-powered headphone amps, just dump the extra heat. But when producing enough wattage to drive speaker loads class A inefficiency quickly becomes problematic and most folks readily accept a "less pure" class A/B design, or some other form of switching amplifier. The reduction in weight, heat, cost, and increase in efficiency is an easy trade for most folks, if not everyone.
Topic: Deity PR-4 Recorder (Read 163,770 times)