| Analog Input The
inputs of both channels are independently
amplified from unity to over 1000 times by trim
pots accessible from the top of the card. Using
sigma-delta modulation, 64 times over-sampling
and a 3-stage digital FIR filter, the DBY3
achieves an 80 dB signal-to-noise ratio. The
anti-aliasing filters automatically track the
sampling rate so that no components have to be
changed with the oscillator. There is no external
triggering capability due to the nature of
sigma-delta converters. A high impedance (1M ohm)
is AC coupled but can be converted to DC coupled
with a jumper wire across each input capacitor.
If the input device requires a +5v bias, such as
a telephone handset, a space is provided for a
resistor on each channel to supply +5v from a
regulated source. This will reduce the input
impedance of the board.
Analog Output
The dual channel D/A converters have 8X
digital interpolation filters which track the
sampling rate set by the on-board oscillator.
They are followed by 64X oversampling sigma-delta
modulators and ultra-linear low-pass filters
which can drive +/-2v into a 600 ohm load.
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