Description:
The Forssell Technologies MADC-2 is an extremely high quality bare-bones, two channel Analog to
Digital Converter (ADC) housed in a 1U rack mount enclosure. A four channel MADC-4 option is
also available. The MADC-2 is designed for the most demanding applications, where capturing
musical performances with accuracy and honesty is required. Output sample rates from 44.1k to
192k Fs are selected with a single front panel switch and with LED indicators showing the selected
sample rate. Digital “clipping” is indicated with a single front panel LED that latches on until the
“reset” switch is pressed. The MADC-2 analog circuitry features an all Class A discrete JFET with no
IC opamps used in the signal path. The analog inputs use high quality XLR connectors. The digital
outputs provided are AES3 (XLR), SPDIF (RCA), and Word Clock output (BNC) are provided. An
additional Word Clock output is available as an option. The MADC-2 digital output word length is
fixed at 24 bits.
The MADC uses an asynchronous decimation filter to provide various standard output sample rates
from 44.1K to 192k. The actual low jitter sampling clock that controls the AD converter chip timing
is permanently set to sample at 192K regardless of output sampling rate selection. This process is
also called Asynchronous Sample Rate Conversion (ASRC) and is performed by a 32 bit sample rate
converter. The output from the ASRC circuitry is 24 bit at the selected output sample rate.
Please note that there are no provisions for word length reduction, level metering with this
converter.
MADC-4 option:
The MADC-4 four channel Analog to Digital converter is housed in the same 1U channel as the
MADC-2, but has two complete MADC converter boards installed with an additional set of input and
output connectors on the rear panel. The second MADC board is uses the output clock from the first
MADC board to insure phase matching of all four channels.
The MADC-4 can be supplied with a single output sample rate selection control, or with two. With a
single sample rate control, the setting on the single front panel control section will control both stereo
ADCs. With two control sections, each ADC’s output sample rate is controlled by its controller
settings. Either way, both ADCs are phase locked.
Word Clock Output:
The MADC-2 and MADC-4 have a single low jitter word clock output available on a rear panel
mounted BNC connector. This output is designed to operate into a 75 ohm terminated coaxial cable.
The output voltage is TTL compatible. The WC output follows the output sample rate, as selected
by the front panel controls. Additional WC outputs are provided on the MADC board, but the user
would have to install their own connectors and wire them to the MADC board.
Output Sample Rate selection:
The output sample rate of the MADC is selected by the single front panel mounted “Select” switch.
The LEDs to the right of this switch indicate the output sample rate currently selected. The MADC
does
not
remember this setting when power is removed. If your sample rate is other than 44.1k
you
must reset the output sample rate to the desired sample rate each time the unit is powered up.
