Lexicon Converter - Manual (Page 28)

Lexicon
24
Using the 20/20 AD
When recording in 4-channel mode to two DAT recorders, it may be useful to
record a "clapper" signal to both DATs to facilitate realignment during post-
production. When you press ALT-LINK, the 20/20 AD will generate 8mS of
silence, followed by an 8-cycle 1 kHz square wave burst at -12dBfs This signal
is time-aligned on all four output channels. You can align the two DAT tapes on
a disk audio production system by visually lining up the first edge of the burst,
or you can align them audibly by subtracting channel 3 from channel 1 and
adjusting the offset until the click disppears.
The 20/20 AD includes a digital sinewave generator which is accurate to 20 bits,
with a dynamic range of more than 120dB. This generator is useful in testing the
digital outputs. To use it:
1. Use the SAMPLE RATE, FORMAT and 4-CHAN buttons to select the output
mode. (These controls are locked out in sinewave generator mode.)
2. Press and hold down 1dB SCALE (ALT)and press the 4-CHAN button. 1dB
SCALE and 4-CHAN will flash to indicate that the unit will now generate digital
sinewaves. The compressor GAIN knob adjusts the frequency of the sine-
wave and the THRESHOLD knob adjusts the amplitude, as shown below.
Realigning Two DAT
Recordings
Digital Sinewave
Generator
3. To turn off the sinewave generator, press and hold down 1dB SCALE (ALT)
and press 4-CHAN. The 20/20 AD will resume normal operation.
Note that in sinewave generator mode, only the compressor GAIN and
THRESHOLD knobs have any effect. Pressing any dual-key combinations other
than ALT—4-CHAN may invoke undocumented diagnostics routines. If you
accidentally get into diagnostics mode, the best way to exit is to turn the power
off, then on again.
(GAIN)
Frequency in Hz
48 kHz Sample Rate
187.5
5062.5
6937.5
9000
11062.5
14062.5
17062.5
20062.5
3000 2062.5
1500
1125
937.5
750
562.5
375
(THRESHOLD)
Level in dBfs
-60
-14
-12
-10
-8
-6
-3
0
-16 -18
-20
-22
-24
-26
-30
-36
(GAIN)
Frequency in Hz
44.1 kHz Sample Rate
172.5
4651
6374
8269
10163.5
12920
15676
18432.5
2755 1895
1378
1033.5
861.5
689
517
344.5