Audio Power DSP System Multiface Manual De Usuario

 

 

User's Guide HDSP System Multiface II

 © RME

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Note: Cubase and Nuendo display the latency values signalled from the driver separately for 
record and playback. While with our former cards these values equalled exactly the buffer size 
(for example 3 ms at 128 samples), the Multiface displays an additional millisecond – the time 
needed for the AD/DA-conversion. 
 
Core Audios Safety Offset 
Under OS X, every audio interface has to use a so called satety offset, otherwise Core Audio 
won't operate click-free. The Multiface uses a safety offset of 32 samples. This offset is sig-
nalled to the system, and the software can calculate and display the total latency of buffer size 
plus AD/DA offset plus safety offset for the current sample rate. 
 
 

 
When activating the Double Speed mode the Multiface operates at double sample rate. The 
internal clock 44.1 kHz turns to 88.2 kHz, 48 kHz to 96 kHz. The internal resolution is still 24 bit. 
 
Sample rates above 48 kHz were not always taken for granted, and are still not widely used 
because of the CD format (44.1 kHz) dominating everything. Before 1998 there were no re-
ceiver/transmitter circuits available that could receive or transmit more than 48 kHz. Therefore a 
work-around was used: instead of two channels, one AES line only carries one channel, whose 
odd and even samples are being distributed to the former left and right channels. By this, you 
get the double amount of data, i. e. also double sample rate. Of course in order to transmit a 
stereo signal two AES/EBU ports are necessary then. 
 
This transmission mode is called Double Wire in the professional studio world, and is also 
known as S/MUX (abbreviation for Sample Multiplexing) in connection with the ADAT format. 
The AES3 specification uses the uncommon term Single channel double sampling frequency 
mode. 
 
Not before February 1998, Crystal shipped the first 'single wire' receiver/transmitters that could 
also work with double sample rate. It was then possible to transmit two channels of 96 kHz data 
via one AES/EBU port. 
 
But  Double Wire is still far from being dead. On one hand, there are still many devices which 
can't handle more than 48 kHz, e. g. digital tape recorders. But also other common interfaces 
like ADAT or TDIF are still using this technique. 
 
Because the ADAT interface does not allow for sampling frequencies above 48 kHz (a limitation 
of the interface hardware), the Multiface automatically uses the Sample Multiplexing method in 
DS mode. One channel's data is distributed to two channels according to the following table: 
 

1 

1a 

1 

1b 

2 

2a 

2 

2b 

3 

3a 

3 

3b 

4 

4a 

4 

4b 

 
As the transmission of double rate signals is done at standard sample rate (Single Speed), the 
ADAT outputs still deliver 44.1 kHz or 48 kHz.