Lexicon M20-20 Quick Reference Guide
20/20 AD Quick Reference Guide
THRESHUNBAL THRESHUNBAL
OVL
0
3
6
12
18
24
30
36
42
60
1
2 3
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
ATTEN reduces input level by
6dB. Use sparingly, and only
on balanced input signals.
THRESHUNBAL THRESHUNBAL
1dB SCALE
ALT
PK HOLD
ATTEN
MUTE
OVL
0
3
6
12
18
24
30
36
M
+
42
C
•
60
P
–
4
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.
Note: Non-linearity of the potentiometer 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 UNBAL light goes out.
~
4 CHAN
EMPH
DISPLAY
RMT
LINK
ON
VID
EXT SYNC allows you to synchronize to an internally derived sample clock, or to an
external AES or Word Clock
signal in the range of 4151kHz.
Note: The Word Clock input is
not transformer-isolated, and requires a ground connection between the 20/20 AD and the signal source.
DIGITAL COMP/LIMITER
6
4
8
10
2
12
0
M
P
C
GAIN
100
mS
-14
-18
-10
-22
-6
-26
THRESHOLD RELEASE
0
+•–
0-36
DITHER
WIDE
20BIT
HF
PL DN
SAMPLE RATE
48
AES
WC
PRES
44.1
SPDIF
AES
LOCK
EXT SYNC
FORMAT
1S10
∞
AES / WC:
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 amplitude. Use this setting when
recording to 20-bit media.
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.
POWER
20/20 AD
20 BIT A/D CONVERTER
Level Meters
When the compressor is
OFF, the behavior of the level
meters is determined by settings of 1 dB SCALE and PK
HOLD.
Switches ON Meters 1 & 2 Meters 3 & 4
4-Channel
Mode
2-Channel
Mode
none
1 dB SCALE
DISPLAY
none
1 dB SCALE
DISPLAY
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.
Normal
1 dB Scale
Gain Reduction
Normal
Normal
Normal
Alternate Modes
ALT-ATTEN will mute the out-
To activate
the alternate modes...
press and hold ...then press one of these.
1dB SCALE
ALT
MUTE
ATTEN
4 CHAN
~
Repeat to exit the alternate mode.
puts. The level meters will still
work.
DISPLAY
RMT
LINK
ON
VID
When the compressor is ON, pressing DISPLAY will cause gain
reduction (in dB) to be displayed on the right two meters (2channel mode) or on all four meters (4-channel mode).
OVL
0
3
6
Normal
1 dB Scale
Gain Reduction
(Blank)
1 dB Scale
Gain Reduction
12
18
24
30
36
42
60
ALT-4 CHAN activates output
of a digital sinewave at the
AES ports.
ALT-DISPLAY activates remote
DITHER
EXT SYNC
mode/front panel lockout. When
activated, the 1dB SCALE and
DISPLAY LEDs flash and front
panel controls are locked into
their current settings.
ALT-ON is reserved for future enhancements.
- red -
- red -
- yellow -
- yellow -
- green -
- green -
- green -
- green -
- green -
- green -
- green -
NORMAL
OVL
0
-3
-6
-12
-18
-24
-30
-36
-42
-60
1dB SCALE
OVL
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
GAIN
REDUCTION
1
2
3
4
5
6
7
8
9
10
11
In 4-channel mode, ALT-LINK
activates a synchronized short
tone burst.
ALT-DITHER activates psychoacoustically optimized
noise shaping. (Disables 4channel mode, compression
and mute functions.)
ALT-EXT SYNC enables the
digital audio input.
© 1994
070-09091 Rev 2
20/20 AD Quick Reference Guide
3 + 4 1 + 2
DO
V ~
Using the Compressor
0dB
-3dB
-6dB
-8dB
-10dB
-12dB
-14dB
-16dB
THRESHOLD
-18dB
-20dB
-22dB
-24dB
-26dB
-30dB
-36dB
1
1.50:1
1.20:1
1.14:1
1.11:1
1.09:1
1.07:1
1.06:1
1.06:1
1.05:1
1.05:1
1.04:1
1.04:1
1.03:1
1.02:1
2
3.00:1
1.50:1
1.33:1
1.25:1
1.20:1
1.16:1
1.14:1
1.12:1
1.11:1
1.10:1
1.09:1
1.08:1
1.07:1
1.06:1
DO
34
4.00:1
2.00:1
1.66:1
1.42:1
1.33:1
1.27:1
1.23:1
1.20:1
1.17:1
1.16:1
1.14:1
1.13:1
1.11:1
1.09:1
4.00:1
3.00:1
2.00:1
1.66:1
1.50:1
1.40:1
1.33:1
1.28:1
1.25:1
1.22:1
1.20:1
1.18:1
1.15:1
1.12:1
5
4.00:1
4.00:1
2.66:1
2.00:1
1.71:1
1.55:1
1.45:1
1.38:1
1.33:1
1.29:1
1.26:1
1.23:1
1.20:1
1.16:1
PUSH
SYNC
GAIN
6
4.00:1
4.00:1
4.00:1
2.50:1
2.00:1
1.75:1
1.60:1
1.50:1
1.42:1
1.37:1
1.33:1
1.30:1
1.25:1
1.20:1
AES
IN
WORD CLOCK
IN
OUT
7
4.00:1
4.00:1
4.00:1
3.33:1
2.40:1
2.00:1
1.77:1
1.63:1
1.53:1
1.46:1
1.41:1
1.36:1
1.30:1
1.24:1
PUSH
8
4.00:1
4.00:1
4.00:1
4.00:1
3.00:1
2.33:1
2.00:1
1.80:1
1.66:1
1.57:1
1.50:1
1.44:1
1.36:1
1.28:1
4IN3
UNBAL
BAL
9
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
2.81:1
2.28:1
2.00:1
1.81:1
1.69:1
1.60:1
1.52:1
1.42:1
1.33:1
PUSH PUSH
10
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
3.50:1
2.66:1
2.25:1
2.00:1
1.83:1
1.71:1
1.62:1
1.50:1
1.38:1
2IN1
11
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
3.20:1
2.57:1
2.22:1
2.00:1
1.84:1
1.73:1
1.57:1
1.44:1
UNBAL
BAL
PUSH
12
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
4.00:1
3.00:1
2.50:1
2.20:1
2.00:1
1.85:1
1.66:1
1.50:1
To minimize the audibility of compression artifacts, use ratios from the unshaded portion of the table.
Dynamic Range Compression
Start with compressor GAIN
set between 4 and 6dB.
Set THRESHOLD between
-18 and -36dB.
Set RELEASE to 100 mS.
Shorten the time constant for
percussive program material
and lengthen it for voice.
Overload Protection
Press PK HOLD and 1dB
SCALE. Set input so that peaks
read approximately -4dB.
Set compressor GAIN to 4dB.
Set THRESHOLD to 0dB.
Start with RELEASE set to
100mS and adjust it for the
program material
Recognizing Machine States
Flashing Machine State Comment
1dB SCALE and ATTEN Outputs muted. To unmute, press and hold 1dB SCALE and press ATTEN.
1dB SCALE and 4-CHAN Sinewave generator mode To exit, press and hold 1dB SCALE and press 4-CHAN.
1dB SCALE and EMPH Diagnostics mode To exit, turn 20/20 AD POWER off, then on again.
1dB SCALE and DISPLAY Front panel lockout To exit, press and hold 1dB SCALE and press DISPLAY.
WC or AES External sync source selected Connect the appropriate sync source or use EXT SYNC to
but not present select Internal Sync (neither WC nor AES lighted).
48 and 44.1 AES sync source not present AES sync source must be within 41-51 kHz range.
or out of range
Continuously Lit
WIDE, HF and 20BIT Psychoacoustically optimized 4-CHAN, DISPLAY, LINK, compressor ON and ALT-MUTE
noise shaping activated are disabled. To exit, press DITHER.
WC, AES, PRES and LOCK Digital audio input enabled Analog input disabled. To exit, press and hold 1dB SCALE
and press EXT SYNC.
3 Oak Park • Bedford, MA 01730 USA • Tel 781-280-0300 • Fax 781-280-0499
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