The full spec optional ADC for OctoPre offer three output formats; AES/EBU, S/PDIF and a simultaneous ADAT output.

The converters are 24-bit and 128x over-sampled, handling sample rates of up to 96 kHz, but can dither down to 20 or 16 bit. All frequency settings and bit rates can be altered from the front fascia, with an ADC lock LED to show when word clock is synchronised.

An external Wordclock input is also provided (BNC connector). The AES/EBU or S/PDIF format outputs can run simultaneously with the lightpipe outputs, giving up to 16 channels of digital output for all sample rates.

• Dynamic Range = 110dB
• Clock jitter = 250 picoseconds
• Clock jitter when synced to an external clock = 1 nanosecond
• THD+N AMPL = -109dBFS 'A' weighted

With converters, as with many other things in life “It’s not how big it is, but what you do with it that counts”. Whether running at 44.1, 48, 88.2, 96 or 192 kHz, or at 16, 20 or 24bit rates, the converter specifications alone are no measure of the quality of the record signal path. Rather, it is a combination of both the converter specifications and the quality of the system that supports it.

Focusrite A/D converter cards are designed to meet the absolute maximum design specifications possible for the converter chip-sets used. However the real benefit comes from using a recording system in which the ADC is included within the closed environment of a single box. The integral closed environment allows a shorter record path to digital, with no
unnecessary analogue connections out of the Focusrite box to the input of the recording equipment. (The receiving equipment will also certainly include more analogue circuitry in the form of gain/trim stages before the external ADC, only further lengthening the record path.)

A further benefit of a single, closed environment relates to the level of unwanted noise in the vicinity of the converter circuitry. Because the Focusrite unit operates as an analogue device right up to the point of the ADC, the environment within which the converter operates is extremely quiet and controlled. It does not contain extraneous clocks, nor other sources of
digital noise, which exist within many digital desks and multi I/O DSP environments. Any of
these may further contribute to the lack of clarity and accuracy.

So, innovative circuitry around the converter, the operation of the circuitry within the host unit, the shorter signal path and a quieter operational environment mean that Focusrite’s
optional A/D converters offer an immense level of performance for the price.