+ In the days of analog tape recording, the routing of monitor signals was + performed with relays and other analog audio switching devices. Digital + recorders have the same feature, but may impart some + latency + (delay) between the time you make a noise and the time that you hear it + come back from the recorder. +
++ The latency of any conversion from analog to digital and back to + analog is about 1.5–2 ms. Some musicians claim that even the + basic A/D/A conversion + time is objectionable. However even acoustic instruments such as the piano + can have approximately 3 ms of latency, due to the time the sound + takes to travel from the instrument to the musician's ears. Latency below + 5 ms should be suitable for a professional recording setup. Because + 2 ms are already used in the A/D/A process, you must use extremely low + buffer sizes in your workstation I/O + setup to keep the overall latency below 5ms. Not all + computer audio systems + are able to work reliably at such low buffer sizes. +
+
+ For this reason it is sometimes best to route the monitor signal
+ through an external mixing console while recording, an approach taken by
+ most if not all professional recording studios. Many computer I/O devices
+ have a hardware mixer built in which can route the monitor signal "around"
+ the computer, avoiding the systemlatency.
+ In either case, the monitoring hardware may be digital or analog. And in
+ the digital case you will still have the A-D-A conversion latency of
+ 1–2 ms.
+