Weiss ADC2 User Manual

digital audio

weiss engineering ltd.
Florastrasse 42, 8610 Uster, Switzerland

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GAMBIT

ADC2

OPERATING MANUAL

Software Version: 3.0

OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER INTRODUCTION

INTRODUCTION

Congratulations on purchasing the Weiss Gambit Series ADC2 A/D Converter !

The ADC2 is a two channel A/D converter de­signed for most demanding audio applications. It
uses state of the art A/D chips in Weiss Engineer­ing’s proven “correlation technique” configura­tion, which lowers converter imperfections and
improves the SNR ratio.

For best noise rejection, the analogue input signal
is kept balanced from the input connectors up to
the converter chips. A high quality microphone
preamp is available as a standard feature.

Additionally, there is a built-in digital two­segment compressor / limiter for optimal level­ling, employing adaptive release timing, look­ahead circuitry and sidechain-oversampling for
mastering-quality dynamics processing.

Large bar graphs, a well thought-out push button
array and uncluttered rotary knobs optimize han­dling ergonomics.

Summary of ADC2 features:

Inputs

• Two balanced LINE and two MIC inputs on
separate XLR connectors.

Synchronization

• Internal sync selectable 44.1kHz, 48kHz,

88.2kHz, 96kHz, 176.4kHz, 192kHz.

• External sync from Wordsync Input (BNC) or
from AES/EBU input.

• Wordsync output on a BNC connector.

Metering

• One input / output level bargraph per channel
with short peak hold

• One gain reduction bargraph per channel.

• Two over LEDs

• Two numerical displays for peak hold and

level settings.

• Reference for level setting can be altered

Outputs

• AES/EBU on XLR in one or two wire format

• S/PDIF on RCA

• Firewire (to be implemented).

DSP

• MIC input with switchable phantom power.

• Input sensitivity is settable in each channel

independently (or ganged) with two rotary
encoders.

• Line Input sensitivity: -16dBu to +26 dBu.

• Mic Input sensitivity: -54dBu to +6dBu.

• Separate AES/EBU input on XLR for synchro-

nization and/or audio input to the DSP, which
allows for use of the ADC2 for redithering
and limiting of digital signals.

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• POW-R dithering to 16 bits, settable to three
different algorithms according to the POW-R
standard.

• SNR enhancement.

• Level bar graph meter.

• Two segment compressor / peak limiter

• Double-precision 40bit floating-point

processing

OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION

OPERATION

ADC2 Block Diagram

Fig. 1 ADC2 Block Diagram Schematic

Input Control Panel

This section describes how to use the input con­trol panel (see Fig. 2).

Fig. 2 ADC2 Input Control Panel

Ganged

For stereo use, press the “ganged” key. This locks
together channel 1 and channel 2 gain and thresh­old controls. Additionally, if “ganged” is active,

active, the compressor / limiter links1 the
sidechains of the two channels. Typical applica­tions for “ganged” mode are

• stereo (left/right) recordings with two micro­phones

• stereo insert limiting (during mixdown or
mastering).

If “ganged” is not active, channel 1 and channel 2
settings are independent and the compressor /
limiter works unlinked. Thus the ADC2 can also
be used in a studio recording / mixing environ­ment as dual channel outboard compressor / lim­iter.

A 3.3ms delay is used by the limiter for preview.

1

“sidechain linking ” means that the same gain reduction is applied

to both channels to avoid corrupting the stereo balance.

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OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION

Digital In

Pressing the “digtial in” key activates the digital
AES/EBU XLR input, the key lights red if active.
As soon as a valid signal is present, the sampling
rate is displayed with the sampling rate keys (see
Fig. 6).

If the digital input stage does not lock to any sig­nal, none of the sampling rate keys are lit.

If the “digital in” key is not lit, the analogue inputs
are selected. To activate the microphone input
for either channel, press the appropriate “mic”
key (if “ganged” is active, pressing one “mic” key
will select microphone inputs for both channels).
Press “+48V” if phantom power is needed.

It is usually advisable to use “low-cut” when re­cording with microphones. If “low-cut” is lit, low
frequency content (traffic rumble, building trem­ors, air-condition hum and other low-frequency
air movement like doors opening or closing near
the microphone etc.) is filtered out.

Peak Hold

If “peak hold” is lit, the numeric display shows the
peak hold value (in dBFS) which is selected by the
gain key: “input gain” selects the input peak hold,
“output gain” selects the output peak hold
(“threshold” also selects output peak hold). See
Fig. 1 for positioning of input and output peak
hold in the processing chain.

If input peak hold is selected, values equal to or
above 0.0dBFS are indicated by “>=0”. The
output peak hold however can measure values
above 0.0dBFS because of the internal floating­point data format used in the digital signal proc­essor. This is very useful to set the output gain.

Input Gain

If “input gain” is lit, the rotary knobs control the
analogue input sensitivity. This is adjusted in 1dB
steps via a relais controlled attenuator. The se­lected value is shown in the numeric display.

The level bargraph is switched between input and
output in the same manner as the peak hold.
Thus, if the “input gain” key is lit, the bargraph
displays the input peak meter. If the “output gain”
key is lit, the bargraph displays the ouput peak
meter (settings can be different if “ganged” is not
lit).

Refer to Fig. 1 on p. 3 for positioning of input and
output peak meter in the processing chain.

Note: The reference for the input sensitivity
display can be chosen by the user. For that pur­pose press and hold the “ganged” key and then
switch the ADC2 on. After a few seconds release
the ganged key. Wait for a few more seconds.
Now you can select the reference with the
righthand knob. This allows to set the reference
to e.g. +4dBu. Factory setting is 0 dBu reference.
When finished press the blinking “peak hold” key.
The setting is retained in non-volatile memory.

Output Gain

If “output gain” is lit, the rotary knobs control the
digital output gain. This gain can be used for op­timal gain adjustment and to drive the peak lim­iter (see below).

The gain ranges from -∞ (off) to +18.0 dB, the
resolution is optimized for fine control around 0.0
dB while still allowing complete fade-out. A spe­cial algorithm is used for click-free gain transis­sions (no “zipper” noise).

To clear the peak hold value, double-click
the “peak hold” key!

Double-click resets both input and output peak
hold.

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OPERATING INSTRUCTIONS FOR GAMBIT ADC2 24Bit / 192kHz A/D CONVERTER OPERATION

0.0

-6.0

-12.0

+6.0

0.0

-6.0

-12.0

0.0

-6.0

-12.0

+6.0

0.0

-6.0

-12.0

0.0

-6.0

-12.0

+6.0

0.0

-6.0

-12.0

Threshold

If “threshold” is lit, the rotary knobs control the
threshold of the compressor section. The value is
shown in the numeric display. If “peak hold” is
active, the output peak value is displayed.

The ADC2 has a two-segment dynamics com­pressor. The threshold can only be adjusted for
the compressor section, which has a fixed ratio of
2:1.

The limiter has a fixed ratio of ∞:1 with a fixed
threshold of 0.0 dBFS.

Because the signal before the output gain
never exceeds 0.0dBFS, the limiter is inac­tive if the output gain is ££££ 0.0dB.

If the threshold is set to 0.0 and the output gain is
below 0.0 the dynamics section is inactive. This
setup is shown in the input vs. output graph in
Fig. 3.

Fig. 3 Compressor with 0.0dB Threshold

To activate the limiter, set the output gain to a
positive value. The boost will drive the signal into
the limiter. The gain reduction applied by the
limiter is visible on the yellow bargraphs.

Fig. 4 Compressor with -3.0dB Threshold

Fig. 5 Compressor with -6.0dB Threshold

The overall gain reduction applied by the com­pressor / limiter is shown in the yellow bargraph.

Note that the compressor uses auto gain make­up: depending on the threshold, a gain is added
after the compressor to ensure that 0.0 dBFS
input results in 0.0 dBFS output (graphically
speaking, auto gain make-up “fixes” the transfer
curve at the (0.0, 0.0) point).

To soften the transmission from linear to limiter
segment, the compressor can be activated by
adjusting the threshold parameter. Fig. 4 shows a
setting with a threshold of –3 dBFS, Fig. 5 shows
–6 dBFS. The range of possible threshold values is
listed on p. 13.

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