There is obviously no analog monitoring with Totalmix. But the latency caused by AD and DA is inaudible. If you have an audible delay, please measure it exactly and check whether it is constant. There must be another reason for the delay, e.g. in your software.
As for "misleading", let me quote what you could have read in the manual of the UCX:
"The term Zero Latency Monitoring has been introduced by RME in 1998 for the DIGI96 series
of audio cards. It stands for the ability to pass-through the computer's input signal at the inter-
face directly to the output. Since then, the idea behind has become one of the most important
features of modern hard disk recording. In the year 2000, RME published two ground-breaking
Tech Infos on the topics Low Latency Background, which are still up-to-date: Monitoring, ZLM
and ASIO, and Buffer and Latency Jitter, both found on the RME website.
How much Zero is Zero?
From a technical view there is no zero. Even the analog pass-through is subject to phase er-
rors, equalling a delay between input and output. However, delays below certain values can
subjectively be claimed to be a zero-latency. This applies to analog routing and mixing, and in
our opinion also to RME's Zero Latency Monitoring. The term describes the digital path of the
audio data from the input of the interface to its output. The digital receiver of the Fireface UCX
can't operate un-buffered, and together with TotalMix and the output via the transmitter, it
causes a typical delay of 3 samples. At 44.1 kHz this equals about 68 µs (0.000068 s), at 192
kHz only 15 µs. The delay is valid for ADAT and SPDIF in the same way.
Oversampling
While the delays of digital interfaces can be disregarded altogether, the analog inputs and out-
puts do cause a significant delay. Modern converter chips operate with 64 or 128 times over-
sampling plus digital filtering, in order to move the error-prone analog filters away from the au-
dible frequency range as far as possible. This typically generates a delay of one millisecond. A
playback and re-record of the same signal via DA and AD (loopback) then causes an offset of
the newly recorded track of about 2 ms.
Low Latency!
The Fireface UCX uses the latest AD converters having an innovative digital filter with a delay of
only 14 samples in Single and Double Speed, and 11 samples in Quad Speed. The DA con-
verter even exceeds these astonishing values with only 7 samples delay in all modes. (...)
Note that the total roundtrip delay of the unit from A to A will be a few samples higher. TotalMix
FX causes an additional delay of typically 3 samples as it stays always within the audio path. "
Regards
Daniel Fuchs
RME
Regards
Daniel Fuchs
RME
