Alesis Hammerfall DSP System manual Settings dialog DDS

Input Status

Displays the state of the current input signal:

•Channel format (64 or 56 channels)

•Frame format (48K or 96K)

•Sample rate (measured)

•Active input (optical or coaxial)

Clock Mode

The unit can be configured to use its internal clock source (Master), or the clock source pre- defined via Pref. Sync Ref (AutoSync).

Pref. Sync Ref.

Used to pre-select the desired clock source. If the selected source isn't available, the unit will change to the next available one. The current clock source and sample rate is displayed in the AutoSync Ref display.

The automatic clock selection checks and changes between the clock sources Word Clock and MADI.

System Clock

Shows the current clock state of the HDSP system. The system is either Master (using its own clock) or Slave (see AutoSync Ref).

11.2 Settings dialog - DDS

Usually soundcards and audio interfaces generate their internal clock (master mode) by a quartz. Therefore the internal clock can be set to 44.1 kHz or 48 kHz, but not to a value in be- tween. SteadyClock, RME's sensational Low Jitter Clock System, is based on a Direct Digital Synthesizer (DDS). This superior circuitry can generate nearly any frequency with highest pre- cision.

DDS has been implemented into the HDSP MADI with regard to the needs of professional video applications, as well as to maximum flexibility. The dialog DDS includes both a list of typical video frequencies (so called pull up/pull down at 0.1% and 4%) and two faders, which allow to freely change the basic sample rate in steps of 1 Hz (!).

Application examples

DDS allows for a simultaneous change of speed and tune during record and playback. From alignment to other sources up to creative effects – everything is possible..

DDS allows to intentionally de-tune the complete DAW. This way, the DAW can match instru- ments which have a wrong or unchangeable tuning.

DDS allows to define a specific sample rate. This feature can be is useful in case the system randomly changes the sample rate – for unknown reasons. It also prevents a change from Dou- ble Speed (96 kHz) to Single Speed (48 kHz), which would cause configuration and routing problems by the changed amount of MADI channels.

The DDS dialog requires the HDSP MADI to be in clock mode Master! The frequency set- ting will only be applied to this one specific card!

Changing the sample rate in bigger steps during record/playback often results in a loss of audio, or brings up warning messages of the audio software. Therefore the desired sample rate should be set at least coarsely before starting the software.

User's Guide HDSP MADI © RME 15