20/20 AD Quick Reference Guide
20/20 AD
POWER
20 BIT A/D CONVERTER
1dB SCALE
ALT
PK HOLD
ATTEN
1
THRESH
UNBAL
THRESH
UNBAL
2
3
THRESH
UNBAL
THRESH
UNBAL
4
4 CHAN
~
EMPH
OVL
0
3
6
12
18
24
30
36
42
60
OVL
0
3
6
12
18
24
30
36
42
60
DISPLAY
RMT
LINK
ON
6
GAIN
8
10
12
4
2
0
-14
-10
0
-36
-18
-22
-26
100
mS
THRESHOLD
RELEASE
DITHER
FORMAT
AES / WC:
SAMPLE RATE
EXT SYNC
DIGITAL COMP/LIMITER
-6
M
C
P
1S
10
0
+
• –
MUTE
∞
VID
+
•
–
M
C
P
WIDE
HF
48
AES
WC
PRES
20BIT
PL DN
44.1
SPDIF
AES
LOCK
© 1993
ALT-DITHER activates psy-
choacoustically optimized
noise shaping. (Disables 4-
channel mode, compression
and mute functions.)
Getting Started
Input Connections
Balanced
Unbalanced
pin
Screen
Screen and
1
(Shield)
Return
pin
Positive
Positive
2
Polarity
Polarity
pin
Return
Open or
3
Return
Make sure the rear panel
BALANCE switches are set
to match the type of input.
(IN = unbalanced; OUT =
balanced) The red UNBAL
light will indicate an error if
there is a mismatch.
EXT SYNC allows you to syn-
chronize to an internally de-
rived sample clock, or to an
external AES or Word Clock
signal in the range of 41-
51kHz.
070-09091 Rev 1
ATTEN reduces input level by
6dB. Use sparingly, and only
on balanced input signals.
ALT-ON is reserved for future
enhancements.
ALT-4 CHAN activates output
of a digital sinewave at the
AES ports.
ALT-ATTEN will mute the out-
puts. The level meters will still
work.
In 4-channel mode, ALT-LINK
activates a synchronized short
tone burst.
ALT-DISPLAY activates re-
mote mode/front panel lock-
out. When activated, the 1dB
SCALE and DISPLAY LEDs
flash and front panel controls
are locked into their current
settings.
1dB SCALE
ALT
4 CHAN
~
DISPLAY
RMT
LINK
press and hold
...then press one of these.
To activate
the alternate modes...
ATTEN
MUTE
ON
VID
Repeat to exit the alternate mode.
DITHER
Note: The Word Clock input is
not transformer-isolated, and re-
quires a ground connection be-
tween the 20/20 AD and the sig-
nal source.
Note: Non-linearity of the poten-
tiometer can cause the signal to
become unbalanced when the
level knob is set to 11:30. To
correct this, turn the knob slightly
in either direction until the UN-
BAL light goes out.
Dither types vary in spectral
distribution of noise:
WIDE produces white noise
HF produces noise whose
amplitude is lower than WIDE
at low frequencies, but higher
at high frequencies.
20 BIT has the same spectrum
as HF, but with lower ampli-
tude. Use this setting when
recording to 20-bit media.
Alternate Modes
When the compressor is
OFF, the behavior of the level
meters is determined by set-
tings of 1 dB SCALE and PK
HOLD.
Press 1dB SCALE to select
1dB scale on level meters.
Press PK HOLD to cause the
level meters to hold at the
highest level received.
none
1 dB SCALE
DISPLAY
Normal
1 dB Scale
Gain Reduction
Normal
1 dB Scale
Gain Reduction
none
1 dB SCALE
DISPLAY
Normal
Normal
Normal
(Blank)
1 dB Scale
Gain Reduction
Switches ON
Meters 1 & 2
Meters 3 & 4
4-Channel
Mode
2-Channel
Mode
1dB SCALE
GAIN
REDUCTION
NORMAL
OVL
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
1
2
3
4
5
6
7
8
9
10
11
OVL
0
-3
-6
-12
-18
-24
-30
-36
-42
-60
- red -
- red -
- yellow -
- yellow -
- green -
- green -
- green -
- green -
- green -
- green -
- green -
OVL
0
3
6
12
18
24
30
36
42
60
When the compressor is ON, pressing DISPLAY will cause gain
reduction (in dB) to be displayed on the right two meters (2-
channel mode) or on all four meters (4-channel mode).
Level Meters
Before switching between Internal and External modes, be
sure to reduce monitor volume, as some D/A converters do
not mute when they lose lock.
