Lexicon 20 - GUIDE REV 1 User manual

20/20 AD Quick Reference Guide
20/20 AD
POWER
20 BIT A/D CONVERTER
1dB SCALE
ALT
PK HOLD
ATTEN
1
THRESHUNBAL THRESHUNBAL
2 3
THRESHUNBAL THRESHUNBAL
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
MCP
1S10
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.
EXTSYNCallowsyoutosyn-
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
ATTENreducesinputlevelby
6dB. Use sparingly, and only
on balanced input signals.
ALT-ONisreserved forfuture
enhancements.
ALT-4 CHAN activates output
of a digital sinewave at the
AES ports.
ALT-ATTENwillmutetheout-
puts.Thelevel meterswillstill
work.
In4-channelmode,ALT-LINK
activatesasynchronizedshort
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
nottransformer-isolated,andre-
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
correctthis,turntheknobslightly
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.
20BIThasthesamespectrum
as HF, but with lower ampli-
tude. Use this setting when
recording to 20-bit media.
Alternate Modes
When the compressor is
OFF,thebehaviorofthelevel
metersisdeterminedbyset-
tingsof1dBSCALEandPK
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.

20/20 AD Quick Reference Guide
Using the Compressor
PUSH
DO WORD CLOCK
IN
DO
3 + 4 1 + 2 OUT
AES
SYNC
IN
V ~
PUSH
4IN3
UNBAL
BAL
PUSH PUSH
2IN1
UNBAL
BAL
PUSH
3 Oak Park • Bedford, MA 01730 USA • Tel [phone] • Fax [phone]
Dynamic Range Compression
0dB
-3dB
-6dB
-8dB
-10dB
-12dB
-14dB
-16dB
-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
34
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
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
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
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
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
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
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
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
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
GAIN
THRESHOLD
To minimize the audibility of compression artifacts, use ratios from the unshaded portion of the table.
Set THRESHOLD to 0dB. Start with RELEASE set to
100mS and adjust it for the
program material
Set compressor GAIN to 4dB.
Press PK HOLD and 1dB
SCALE.Setinputsothatpeaks
read approximately -4dB.
Overload Protection
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
Set THRESHOLD between
-18 and -36dB. Shorten the time constant for
percussive program material
and lengthen it for voice.
Set RELEASE to 100 mS.
Start with compressor GAIN
set between 4 and 6dB.
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.