RME Audio Advanced Remote Control Guía de usuario descargar pdf (Pagina 105)

User's Guide Fireface UCX © RME

105

To use FireWire as efficiently as possible, the Fireface allows to reduce the number of trans-

ferred channels. Limit Bandwidth provides four options, limiting the transmission internally to 18,

14, 10 or 8 channels. This limitation is independent from the sample rate. As can be seen in the

following table, in 192 kHz mode there is no difference between the setting All Channels and

An+SP+ADAT 1-4, as the Fireface UCX offers only 12 channels in Quad Speed mode anyway.

Limit Bandwidth 48 kHz (18) 96 kHz (14) 192 kHz (12) FireWire

Channels

All Channels x x / 18

An+SP+ADAT 1-4 x x / 14

Analog+SPDIF x x x 10

Analog x x x 8

37.5 DS - Double Speed

When activating the Double Speed mode the Fireface UCX 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 (Sample Multiplexing) in connection with the ADAT format.

Because the ADAT interface does not allow for sampling frequencies above 48 kHz (a limitation

of the interface hardware), the Fireface UCX automatically uses Sample Multiplexing in DS

mode. One channel's data is distributed to two channels according to the following table:

Analog In 1 2 3 4 5 6 7 8

DS Signal

Port

1/2

ADAT

3/4

ADAT

5/6

ADAT

7/8

ADAT

- - -

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.

37.6 QS – Quad Speed

Due to the small number of available devices that use sample rates up to 192 kHz, but even

more due to a missing real world application (CD...), Quad Speed has had no broad success so

far. An implementation of the ADAT format as double S/MUX results in only two channels per

optical output.

In Quad Speed mode the Fireface UCX automatically uses Sample Multiplexing. One channel's

data is distributed to four channels according to the following table:

Analog In 1 2 3 4 5 6 7 8

QS Signal

Port

1/2/3/4

ADAT

5/6/7/8

ADAT

- - - - - -

As the transmission of quad rate signals is done at standard sample rate (Single Speed), the

ADAT output still delivers 44.1 kHz or 48 kHz.

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