Sphynx User Manual
© 2000 Merging Technologies
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1 - Analog I/O Level
This parameter chooses between Calibrated analog I/O level (+24 dBu for 0dBFS) or Custom analog I/O level.
The Custom I/O level allows the analog I/O levels to be set, using the top trimmers, to match any studio needs.
This selection is global to all analog I/O modules. It is not possible to configure each module separately.
By default, the Sphynx unit is set to Custom I/O level. All analog module trim-pots are set at the factory to the
following values:
Input Level = + 18 dBu for 0 dBFS (+4 dBu with +14 dB of headroom).
Output Level = + 18 dBu for 0 dBFS (+4 dBu with +14 dB of headroom).
Using the Trim Pots
The Sphynx top cover has drilled holes, which allow the analog level trimmer pots to be adjusted without the need to
remove the top cover. Any small standard tip screwdriver can be used to adjust the desired trimmer pot. The layout
pictured below is also silk-screened on the Sphynx top cover. The number below corresponds to the associated
module, marked IN for input module and OUT for output module.
2 - Analog Input Dither
When enabled, this provides real-time noise shaped dithering on all
S96\IM
analog input modules, by adding a
psychoacoustic noise-shaping filter, which subjectively truncates the A/D converter outputs to 16, 18 or 20 bits,
while 24-bit sound quality is preserved.
To remove the distortion associated with the truncation to a word length lower than 24 bits, a noise shaped dither
adds some noise energy to the incoming analog signal. To minimize the audibility of this added noise to the human
ear, a noise shaping filter is used to minimize the noise level where the human ear is most sensitive (500 to 4000 Hz),
and augment it in where the human ear is less sensitive. One side effect of such a process is however to significantly
increase the peak noise level as measured by most digital audio peak meters (as those used in Pyramix).
A peak noise of about -60 dBFS is therefore normal for a 16 bit dithered signal.
This option should only be used when the destination digital format is limited to 16, 18 or 20 bit word length.
3 - AES-EBU Input SRC
This enables or disables the Sample Rate Conversion available on the AES-EBU input modules.
This selection is applied to all the AES-EBU input modules. It is not possible to configure each module separately.
Note that, for obvious reasons, it is not possible to lock to an AES-EBU input module when the SRC is selected.
In the latter case, only locking to an AES REF sync input is supported.
Using the Sample Rate Conversion
The Sample Rate Converter is very easy to use, as you just have to set the parameter 3, and all AES input modules
will be configured in the SRC mode.
Once in this mode, all incoming AES-EBU signals connected at the input modules will be converted to the Sphynx
sample rate.
Example:
The Sphynx working sample rate is set at 48 KHz
Any AES-EBU input signal of 32 KHz, 44.1 KHz or 48 KHz can be used and will be converted to 48 KHz.
Current SRC limitations are:
•
The upsampling has a limitation of a sample rate input/output ratio of 1:5. This allows any sample rate five times
lower that the current Sphynx sample rate to be converted.
•
The downsampling has a limitation of a sample rate input/output ratio of 1:0.85. This allows 48 KHz material to
be downsampled to 44.1KHz.
•
Does not currently support ‘x2’ SR mode.
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