RME Audio Hammerfall HDSP 9652, User Manual

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User's Guide HDSP System HDSP 9652
© RME
26.5 Recording a Subgroup (Loopback)
TotalMix supports a routing of the subgroup outputs (=hardware outputs, bottom row) to the
recording software. Unfortunately this feature is
not available with the HDSP 9652 , as the
FPGA of the card has no resources left for a hardware implementation. Therefore this chapter
describes the loopback mode when used with an external cable loop.
A loopback is used to record the playback signal. This way, complete submixes can be re-
corded, the playback of a software can be recorded by another software, and several input sig-
nals can be mixed into one record channel. Please note these important issues:
The connection of digital output and input generates a clock loop, and with this a malfunc-
tion, in case the card has not been switched into clock mode Master, or an external clock
signal of highest priority is used.
The latter is the case when the card is in
AutoSync mode, and is synchronized by an external
clock signal from the input selected in Pref Sync Ref . For example set up a loopback cabling
with SPDIF or ADAT3, but clock the HDSP 9652 via input ADAT1.
Connecting digital output and input can cause a digital feedback, which is more severe
than any analog one. Caution!
This is a problem for both TotalMix (monitoring an input signal to the same output channel) and
the DAW software (which usually activates monitoring in the same way).
Recording a Software's playback
In real world application, recording a software's output with another software will show the fol-
lowing problem: The record software tries to open the same playback channel as the playback
software (already active), or the playback one has already opened the input channel which
should be used by the record software.
This problem can easily be solved. First make sure that all rules for proper multi-client operation
are met (not using the same record/playback channels in both programs). Then route the play-
back signal via TotalMix to a hardware output in the range of the record software, and send it to
the record software via the loopback cable.
Mixing several input signals into one record channel
In some cases it is useful to record several sources in only one track. For example when using
two microphones when recording instruments and loudspeakers, TotalMix loopback saves an
external mixing desk. Simply route/mix the input signals all to the same output (third row), then
send this output to a record channel via the loopback cable. This way any number of input
channels from different sources can be recorded into one single track.
Note: The data recorded using the loopback cable is delayed by about 3 samples. This value is
extremely low, because the HDSP 9652 provides digital interfacing only. And therefore the addi-
tional delay can simply be ignored.