Lexicon PCM 42 User manual

pem 42
digital delay processor
Owner's Manual

TABLE OF CONTENTS
SECTION ONE — INTRODUCTION
1.0 Description
1.1 Precautions
SECTION TWO — CONTROLS & INDICATORS
2.0 Introduction
2.1 Front Panel
2.2 Rear Panel
SECTION THREE — INSTALLATION
3.0 Mounting
3.1 Power Requirements
3.2 Audio Signal Connections
3.3. Audio Control Jacks
3.4 Operating Levels
3.5 Non-Audio Remote Control! Functions
3.6 Clock Output
3.7. Voltage Changeover
SECTION FOUR — APPLICATIONS
4.0 Interconnecting the PCM 42
41 General Application Notes and Set-ups
4.1.0 Introduction
4.1.1 Echo
4.1.2 Double Tracking
4.1.3 Flanging
4.1.4 Resonant Effects
4.1.5 Vibrato
4.1.6 Pitch Twisting
4.1.7 Stereo Image Placement
4.2 Special Applications of Long Delay
4.2.0 Introduction
CO
4.2.1 Layering and the Infinite Repeat
Mode
4.2.2 Looping Techniques for Live
4.3 Programming and Using the Metronome/
Clock Output
4.3.1 Setting the Clock Rate
4.3.2 Interfacing the Clock with Rhythm
Machines
44 Interfacing to Other Units
45 Delay Lines in Distributed Sound
Reinforcement Systems
SECTION FIVE — BLOCK DIAGRAM
SECTION SIX — SPECIFICATIONS
6.0 Test Conditions
6.1 General Performance
6.2 Interface Information
6.3 Controls and Indicators
6.4 Power and Dimensions
SECTION SEVEN — IN CASE OF DIFFICULTY
7.1 General
7.2 Unit Will Not Power Up
7.3 Unit Powers Up, Gives Improper Display
7.4 Unit Powers Up, But Will Not Pass Audio
7.5 Returning Units For Repair
7.6 Replacement Parts
7.7 Limited Waranty

1.0 DESCRIPTION
The PCM 42 is a high-performance digital delay
line/ processor that features up to 2.4 seconds of high
quality audio delay, expandable to 4.8 seconds with
optional memory. Delay times are indicated by a highly
accurate numeric display, which provides rapid tracking
of ALL changes in delay time. The PCM 42 includes ver-
satile audio patching and remote control facilities, and a
unique synchronizing clock feature that allows highly
musical usage of the very long delays of which it is
capable. Long repeat loops and layering effects which
were formerly confined to the studio may now be used
easily and reliably on stage.
The 42 provides superior audio performance through
Lexicon’s proprietary method of analog-to-digital
encoding. An increased sampling rate gives wider band-
width without aliasing effects. In addition, a new “‘soft-
knee” limiting circuit eliminates the unpleasant distortion
that most digital circuits generate when overloaded.
The PCM 42’s excellent sonic quality, unique features,
light weight, flexibility and ease of use make it the
perfect choice either on stage or in the studio.
1.1 PRECAUTIONS
Although the PCM 42 is a very well-behaved device,
precautions consistent with good practice for any piece
of audio gear should be observed as a matter of course.
SECTION ONE
INTRODUCTION
Before turning the PCM 42 on or off, it is advisable to
lower the volume on your power amplifier or monitoring
system to avoid undesirable transients.
Never connect power sources or audio power
amplifiers directly into ANY of the PCM 42’s phone
jacks. The PCM 42’s inputs are designed for line level
signals. If a guitar amplifier is used as a signal input,
then a suitable attenuator pad must be used to lower
the level of the feed to the PCM 42.
To prevent fire or shock, never operate the PCM 42 in
the rain or in exposed wet locations.
Please read Section Three UNSTALLATION) of this
manual before operating the PCM 42.
WARNING
ALL SERVICING OF THE PCM 42 SHOULD BE
PERFORMED BY QUALIFIED SERVICE PER-
SONNEL. THERE ARE HAZARDOUS
VOLTAGES LOCATED UNDER BOTH THE
TOP AND BOTTOM COVERS OF THE UNIT.
TO AVOID ELECTRICAL SHOCK, REMOVE
THE POWER CORD BEFORE REMOVING
COVERS. SERVICING PROCEDURES CON-
SISTENT WITH GOOD SAFETY PRACTICE
SHOULD BE USED AT ALL TIMES.

SECTION TWO
CONTROLS & INDICATORS
2.0 INTRODUCTION
ly describes the PCI
ee A a AA
aicators. More cet
d applications is conta
2.1 FRONT PANEL
E
F
GH
J
M
P
VW
Figure
2.1 —
PCM
42
Front
Panel
When
the
button
is
out,
the
unit
is
set
for
the short
Re nEROROOM lore range (O0-1200 ms standard, 0-2400 ms with memory op-
The HEADROOM display monitors the audio level tion) and 16 kHz bandwidth. Pushing the button selects
after the INPUT LEVEL and FEEDBACK controls. The the long range (0-2400 ms standard, 0-4800 ms with
display has 5 LEDs which indicate peak levels relative to memory option) with 6 kHz bandwidth, illuminating the
converter overload. The input stage operates normally 6 kHz LED (Fig. 2.1, Q). The numeric delay display
up to 3 dB below the absolute limit, where a 5:1 com- always indicates the actual delay time.
pression ratio comes into play. At 0 dB, the input stage
limits, and further increases in input level will produce C. INPUT LEVEL
no additional input to the digitizer. Even extreme input
levels produce only a soft distortion, rather than clip-
ping. The Headroom Display follows the compressor/
limiter, indicating the audio level actually seen by the
analog-to-digital converter; thus it becomes non-linear
with respect to the input signal when the O-dB LED is lit.
The INPUT LEVEL control adjusts the input gain for
proper matching of the PCM 42’s sensitivity to the input
signal. Set this control so the HEADROOM display
occasionally indicates 0 dB on program peaks, with
average levels at about -12 dB (in the green zone).
NOTE: A rear panel switch provides an additional
BE PEEE TENGE 20 dB of gain for low level inputs, such as the output of
The DELAY X2 switch determines whether the PCM an instrument pickup. For details, see Section 2.2,
42 is in the short (X1) or the long (X2) time delay range. paragraph “|”.

D. FEEDBACK
cloc k\ wise feeds the
Be WECUY FILTER
Engaging the HI CUT
ne OONG low-pass f Nee i
back path. This is useft
aiat ing room am bien CE
ness of highl ly reson
Engag
reverses
fed bac
back signal ats phase c Bich acter
and is typically used for resonant fenuingss sounds:
G. DLY INV
Engaging the DLY INV (Delay Invert) button reverses
the polarity of the delayed sound which ts fed to the
OQUTPUT MIX control (Fig. 2.7, 1).
H. BYPASS LED
In Bypass mode, the Delay signal is cut out of the mix
at the MAIN OUTPUT, and all input to the delay line is
cut off. This LED is illuminated when the BYPASS is ac-
tivated by the optional footswitch or an external logic
signal.
|. OUTPUT MIX
The OUTPUT MIX control establishes the ratio of
direct to delayed sound in the PCM 42 MAIN OUTPUT.
Full counterclockwise position (toward INPUT) provides
100% direct sound from the input preamplifier. Full
clockwise position provides 100% delayed sound. The
control is detented in center position, where the blend
of signals is equal. This point is calibrated for maximum
notch depth during flanging.
J. © RPT
The INFINITE RPT pushbutton causes the PCM 42 to
capture the sound in the delay memory at the first clock
pulse after the button is pressed and repeat that seg-
ment continuously until the button is pressed again
The repeat mode uses the entire delay memory — the
length of the captured segment is independent of the
delay tap selected with the UP and DOWN pushbut-
tons, but changes with the settings of the MANUAL
VCO-SWEEP control and the DELAY X2 pushbutton.
ise ae the infinite repeat mode is enabled not at
nt the button is pressed, but at the first clock
cree (as Ow He the flashing CLK LED at the right of
he di / that time. To See rapid entry into this
rate To a sma
delay time lene section K, below!
il fraction of the total
TI ill not power up in repeat mode. If the
INFINITE RPT button is “IN” at time of power up, the
‘ll not enter the : Ae eat mode until the pushbutton
is released ane press
selected throu
to the rear pane
ee Repeat mode can also be
ry-contact switch attached
REP EAT jack (Fig. 2.2, D}.
K. SET-MODE
The SET-MODE slide sv vitch determines the function
of the display and the U P ag d DOWN pushbuttons. In
normal operation, this switc “ s set to DLY (left) and the
display shows the delay time in milliseconds, while the
pushbuttons increment and decrement the delay tap
selection.
With the SET-MODE switch in the CLK (right) posi-
tion, the UP and DOWN pushbuttons change the rate
of the flashing CLK LED and of the pulses appearing at
the CLOCK output. In this mode, the display indicates
the period of the clock as a fraction of the maximum
delay time (as determined by the DELAY X2 and the
MANUAL VCO-SWEEP settings). The numerator of the
fraction is on the left, the denominator on the right. The
DOWN button cycles the numerator through odd in-
tegers 1, 3, 5, 7, and 9. The UP pushbutton causes the
denominator of the fraction to cycle through binary
values 1, 2, 4, 16, 32, and 64.
L. DOWN BUTTON — DELAY/CLOCK
The DOWN pushbutton decrements the delay tap
value or the denominator of the CLOCK output ratio, as
described in paragraph ‘‘K’’ above. With the SET-
MODE switch in DLY, a short press and release of the
button will decrease the delay time by one increment. If
the button is held in, the selection will decrease approx-
imately once per second. To move rapidly to a new set-
ting, the UP button may be pressed while continuing to
hold DOWN. When UP is released, the increment rate
reverts to once per second.
M. UP BUTTON — DELAY/CLOCK
The UP pushbutton increments the delay tap value or
the numerator of the clock ratio as described above in
paragraphs “’K"’ and “L’’. As with DOWN, the rate of
increase of the delay time may be accelerated by press-
ing DOWN while holding UP. Thus, the direction of
change is determined by which button is pressed first,
while the rapid mode is enabled by the opposite button.

N. DELAY DISPLAY
When the SET-MODE switch is in the DELAY posi-
tion, the DELAY DISPLAY gives a precise 4-digit
display of the actual Gelars ime in milliseconds. With the
SET-MODE switch at CLOCK, it shows display of the
clo ae eee {see seca K above). The delay time
disp is accurate and updates itself very quickly,
stewines it to track all sweep functions as fast as the eye
can follow.
O. CLK LED
The CLK LED flashes in synchrony with the CLOCK
UTPUT on the rear panel. The rate at which the la amp
he is determined by the fraction programmed v os
SET-MODE, DOWN and UP, coupled with the settin
of the VCO-SWEEP controls.
To determine the exact period of the CLOCK, step
the delay tap value upward with UP until the display
ceases to increment, indicating maximum delay time.
(Use the fast-forward function described in paragraphs
K and L.) Note the delay time, and then switch SET-
MODE to CLOCK and read the display as a fraction,
with the numerator on the left and the denominator on
the right. The clock period is equal to the delay time
times the clock fraction. Note that if DEPTH is not set to
QO, or an external modulation is present, the clock rate
will not be stable.
P. co LED
The INFINITY LED is illuminated whenever the repeat
mode is selected by the INFINITE RPT pushbutton or
the corresponding footswitch jack.
Q. 6 kHz LED
The 6 kHz LED lights when the long delay mode is
selected by DELAY X2, indicating a reduction in band-
width to 6 kHz and a doubling of the available range of
delay.
R. MANUAL VCO-SWEEP
The MANUAL VCO-SWEEP control provides con-
tinuous, smooth control of delay times over a range of 3
to 1 by modifying the sampling rate. This control func-
tions as a,manual modulation for flange, chorus and
pitch twisting effects, and for access to very long delay
times.
S. DEPTH
The DEPTH control adjusts the amount of internal
modulation of the VCO, affecting the depth of sweep
r or flange, chorus and pitch-twisting. When DEPTH is
set at “O"', the internal sweep Is inactive. As the DEPTH
control
.
advanced
clockwise
toward
‘'10",
the
range
of the sweep increases to a maximum clock ratio of 3:1.
The DEPTH control interacts with the MANUAL
¥CO-SWEEP control (Fig. 2.1-R). The MANUAL con-
trol has its maximum effect with the DEPTH at 0", and
no effect with the DEPTH control at 10".
T. WAVEFORM
The WAVEFORM control selects the
modulation:
type of VCO
1. Full counterclockwise rotation selects sinusoidal
modulation: the delay time smoothly increases
and decreases at a speed governed by the RATE
setting.
2. Setting the control at the center detent selects
envelope-follower modulation: the delay time
changes in response to the level of the input
signal.
3. Full clockwise rotation selects square-wave
modulation: the delay time jumps instantaneously
up and down according to the setting of the RATE
control.
4. Intermediate positions of the control blend either
sinusoidal or square-wave modulation with
envelope-follower modulation.
U. RATE
The RATE control adjusts the low-frequency
oscillator (LFO) that controls the frequency of the sine-
or square-wave modulation. With the WAVEFORM
control in the center (envelope-follower) position, the
RATE control will have no effect.
V. RATE LED
The RATE LED flashes on and off to indicate the rate
of the LFO and to allow playing in synchronization with
the delay sweep.
W. POWER SWITCH
This latching pushbutton turns the AC power on and
off. On power-up, the delay time is automatically set to
O ms, the infinite-repeat function is turned OFF, and the
clock ratio is set to a value of 1/2. All other switch and
control settings remain as they had previously been set.

2.2 REAR PANEL
Figure 2.2 — PCM 42 REAR PANEL
A. POWER CONNECTOR
The POWER connector accepts standard IEC power
cords. Before plugging in the AC cord and applying
power, check the adjacent d plate to ensure that the
set operating voltage matches that of the AC mains.
B. VCO REMOTE JACK
The VCO input jack allows remote operation of the
MANUAL VCO-SWEEP control by means of a foot con-
troller (optional), or an externa! control voltage (range O
to +10 Volts; O Volts = maximum delay, + 10 Volts
= minimum, linear over a range of 3:1). The VCO jack
accepts a standard 1/4” phone plug for control
voltages, or a stereo tip/ring/sleeve plug when used
with the optional foot controller (Lexicon A-CP-41 Foot
Pedal). When the plug is inserted, the MANUAL VCO-
SWEEP is bypassed and has no effect.
C. BYPASS SWITCH JACK
The BYPASS function provides a means of quickly
switching the delay signal out of the MAIN OUTPUT
mix, while at the same time killing the feed to the delay
circuitry itself. The BYPASS jack accepts a 1/4” phone
plug and the BYPASS is activated when the tip of the
plug is shorted to the sleeve, or when a TTL logic ‘0" is
present at the tip.
D. co REPEAT SWITCH JACK
The INFINITE REPEAT function is activated by a
momentary switch closure or the falling edge of a TTL
compatible clock pulse. The unit remains in repeat
mode until another closure or pulse arrives OR the front
panel INFINITE REPEAT pushbutton (Fig. 2.1, J) is
released from a depressed position. The BYPASS func-
tion and the INFINITE REPEAT mode may be controlled
with a single Lexicon A-FS-41 Dual Footswitch
Assembly, or any combination of one latching
(BYPASS) and one momentary-contact (INFINITE
REPEAT) switch.
E. CLOCK OUTPUT JACK
The CLOCK OUTPUT jack provides a TTL-compat-
ible square wave output suitable for clocking many
automatic rhythmic devices and sequential controllers.
The rate of the clock is a fraction of memory Capacity at
the current sampling rate, programmable from the front
panel. This allows synchronization of external devices
to the delay period. (See Sections 3.6 and 4.3.2.)
F. DELAY OUTPUT JACK
The DELAY OUTPUT is an unbalanced tip/sleeve
jack carrying the output of the delay line at line level,
unmixed with any of the direct signal. (See Sections 3.2
and 4.4.)
G. DIRECT OUTPUT JACK
The DIRECT OUTPUT is an unbalanced tip,’sleeve
jack which carries only the input signal after preampli-
fication. This signal is at system line level.
H. INPUT JACK
The INPUT jack is a balanced, differential input which
accepts a 1/4” tip/ring/sleeve phone plug; unbalanced
sources can be accommodated by simply substituting a
tip/sleeve phone plug. A high input impedance allows
the PCM 42 to interface with either low or high im-
pedance sources.
|. GAIN SWITCH
The GAIN Switch matches the PCM 42's ‘nput sen-
sitivity to the signal source. Engaging the switch in-
creases sensitivity by 20 dB for sources such as electric
pickups, high-output microphones, and some electronic
instruments.
J. FEEDBACK CONTROL JACK
The FEEDBACK CONTROL jack provides two distinct
functions. When used with a tip/ring/sleeve plug and a

n onan 41) or any potentiometer, the
o the ee remotely. it can
uxillary input which is combined
without gain conte (nominal line
ions 3.3 and 4.2.2
A ss main |
= =
ae)
eS
See Secti
NOTE: THIS FUNCTION IS INDEPENDENT OF THE
F ai NT PANEL FEEDBACK CONTROL. RUNAWAY
DBACK CAN RESULT IF BOTH CONTROLS ARE
RAISED AT THE SAME TIME.
K. MIX CONTROL JACK
Like the FEEDBACK CONTROL, the MIX CONTROL
jack { ai 35 dual functions. With a potentiometer o
foot pedal, the user can raise and lower the volume
the delayed signal in the MAIN OUTPUT mix. ae
delay effects can be faded in and out at will. This jack
can also be used to inject an external signal into the out-
put mix. (See Sections 3.3 and 4.2.2.)
L. MAIN OUTPUT
The MAIN OUTPUT is an unbalanced tip/sleeve jack
whose signal level is determined by the adjacent con-
trol. It carries the blend of di rect and processed signal
which is set with the front panel OUTPUT MIX control
(Fig. 2.1, I).
f
M. OUTPUT LEVEL
The OUTPUT LEVEL control adjusts the MAIN OUT-
PUT level from its maximum of +179 dBV (9 V rms)
down to full attenuation. This control should be ad-
justed to provide the maximum level to the monitor
system, amplifier or console without clipping its input
stage.

ADEQU
TOM AND , whether or not it 's
k-mounted, This is of particular importance if the
s mounted above power ampli er heat
gener: 2Ng gear.
Since the PCM 42 processes low-level audio signals,
if iS advisable to locate it away from strong elec-
tromagnetic fields, such as those generated by power
transformers, motors, fluorescent ballasts, etc.
3.1 POWER REQUIREMENTS
The PCM 42 is set at the factory to operate at either
100, 115, or 230 volts (50 - 60 Hz). The factory-set
voltage is indicated on the rear panel next to the power
receptacle. The maximum power required is 20 watts.
Units set for 100 or 115 volts are fused at 1/4 ampere,
230-volt units at 1/8 ampere.
THE OPERATING VOLTAGE SHOULD NOT BE
CHANGED EXCEPT BY A QUALIFIED SERVICE
TECHNICIAN.
The PCM 42's power cord has a standard three-pin
IEC connector to simplify adaptation to power sources
in various countries, and to provide chassis-to-mains
grounding according to accepted safety standards.
SECTION THREE
INSTALLATION
3.2 AUDIO SIGNAL CONNECTIONS
r stereo (or
>} Plugs for Input
ad this Ssupsection fo
or foot pedal cor é
e proper cable for each
ensure that YOU are
function.
IGE UTD ruSsed WA
g (Tip = signal high, | Ring = signal iow,
Sleeve = shield ground).
it can aiso be used with unbalanced input sources
when fed by a T/S phone plug (Tip. = signal high,
Sleeve = sana ow! shi ield). This creates a traditional
single-ended inpu
NOTE: if a T/R/S plug is used with a
source, be sure to short the ring and sl
together.
single-ended
eeve terminals
OUTPUTS
The MAIN, DIRECT and DELAY audio outputs (Fig.
2.2, L, G and F) are unbalanced (single-ended), and are
intended for use with a T/S phone plug. Load im-
pedances of 5 kilohms or higher can be driven to full
levels; loads as low as 600 ohms may be driven without
loss of signal quality, although the output level will be
reduced slightly. lf the PCM 42 is used to drive
microphone level inputs from the DIRECT or DELAY
outputs, it will be necessary to insert a 20- or 30-dB pad
at the input to the driven device. The MAIN OUTPUT
has its own level control.

3.3 AUDIO CONTROL JACKS
The PCM 42 has two audio control jacks which are
wired in T/R/S configuration. In both of these, the
sleeve iS a common ground, and a single-ended, buf-
fered delay output appears on the ring. The tips of the
jacks are connected to different input patch points in
the PCM 42.
FEEDBACK CONTROL JACK (Fig. 2.2, J)
The tip terminal of this eo is connected to a patch
point that is mixed with the main INPUT. The input ac-
cepts single-ended, lin Bega ee from a source of any
impedance. Connecting a Lexicon A-CP-41 foot pedal
to this jack places the foot pedal’s internal poten-
tiometer between the ring and the tip, mixing the delay
output with the main input and thus allowing remote
control of feedback or regeneration.
Since the delay-only output on the ring is bu
two-way T/S phone plug may be inserted in thi
mix any other line-level signal with the mai i
without compromising the delayed signal. A T/RY
plug with connections to the ring and sleeve only will
permit the use of either audio control jack as a separate
delay-only output.
="
et
¢
Pe
a
mA&ow
NOTE: The feedback loop enabled by this control
jack iS separate from, and operates in parallel with, the
front panel FEEDBACK control and its associated HI-
CUT and FB INV switches. If the two controls are used
simultaneously, runaway feedback (howling) can occur.
When using the FEEDBACK CONTROL jack with the
foot pedal, turn the front panel FEEDBACK control to 0.
MIX CONTROL JACK (Fig. 2.2, K)
Inserting a phone plug into this jack interrupts the
connection of the delay signal to the OUTPUT MIX con-
trol on the front panel. A foot pedal plugged into this
jack allows the performer to fade the delay effects as
desired from zero up to the setting of the OUTPUT MIX
control. This jack may also be used to insert other signal
processors, ane as equalizers, into the path of the
delayed signal. The input accepts single-ended, line-
level audio from a source of any impedance.
3.4 OPERATING LEVELS
INPUT LEVELS
The PCM 42 can handie a wide variety of input
sources including microphones, electric instruments,
mixer outputs and so on. The high-impedance delay line
input will operate equally well with low- or high-
impedance sources. It is important, however, to set the
10
input sensitivity So that the unit can acco
full dynamic range of the source
i aye e; ~
signa ai/noise ratio and
mmodate the
with
£
To match the PCM 42's sensiti the
source, ae must first set
rear panel. Push the button in (selecting 20 a of extra
ae cee when using sour ue with peak levels ranging
from -23 dBV to 0 dBV (0.07 V to 1.0 V rms). This in-
cludes electric pickups, high output mireropuene coe
level mixer outputs, and some electronic instr pices
instrument preamplifier outputs.
ivity to
input
the 20 dB GAIN switch on the
O
I noul
Ihe button should be out
sources with peak levels rangir
70V to 9.0 Vrms}. This
output Ss, some
puts and some
(unity gain} when using
ng from -3 dBV to +19
includes high level mixer
e electronic instrument/preamplifier out-
direct box outputs.
With the appropriate switch position engaged, adjust
the front panel INPUT LEVEL control for peak
HEADROOM displays of 0 dB, with average levels
around -12 dB.
vel is unknown, Start at the 0 dB
out), and adjust the INPUT
i to otk g the HEADROOM display within
desi red paniaes f the gain is insufficient to achieve
peaks of -6 dB with Ae INPUT LEVEL at maximum, turn
dov he INPUT LEVEL and engage the +20 dB
positio
re signal ley
: iE itimm fA:
SATIN Eee? 1 (Dutton
WARNING
NEVER CONNECT THE PCM 42 INPUT
DIRECTLY TO POWER SOURCES, IM-
PROPERLY ISOLATED AC/DC DEVICES, OR
POWER AMPLIFIERS. DISREGARDING
THESE PRECAUTIONS CAN LEAD TO ELEC-
TRICAL SHOCK, AND MAY DO SEVERE
DAMAGE TO THE PCM 42.
MAIN OUTPUT LEVEL
The PCM 42 MAIN OUTPUT is designed to drive
loads of 5 kilohm or higher impedance at a level of 9 V
rms (+18 dBV). It is possible to drive impedances as
low as 600 ohms, although maximum output level is
reduced to about 5 V rms (+ 14 dBV).
NOTE: Do not use-the INPUT LEVEL control to set
output level.
Once the proper input level is established, the rear
panel OUTPUT LEVEL control can be used to adjust the
MAIN OUTPUT level for a wide range of devices. In
general, best signal-to-noise performance results at set-
tings of mid-scale or higher.

WARNING
THE PCM 42 OUTPUTS ARE PROTECTED
AGAINST SHORT CIRCUITS, BUT SHOULD
NEVER BE CONNECTED TO SIGNAL
SOURCES.
AUXILIARY INPUT AND OUTPUT LEVELS
The DIRECT an
a % A * erin Soeaan path ae +R BAAS
1d DELAY outputs, as weil as the delay
3.5 NON-AUDIO REMOTE CONTROL
FUNCTIONS
BYPASS LAT CHE }
SWEEP
. ;, ‘ ROM
eg eons 'e Sure
tw Seas
ue tputs on the rin
gs of th
a acks h
x)
als
7 € e thei r ae le euiel
eae “Rede
are nominal ally 3.5 Vrms (+11 dBV) for
full input level.
The audio patch points connected to the tips of the
audio control jacks are impedance, line level (+ 11
dBV maximum), single-ended
vat’ ~
Inpu ts,
FEEOBACK MEX
eo : ae
es fo ae eee 8
2 oo 6
Lee
Figure 3.1 — FOOT PEDAL DIAGRAM
Three rear panel phone jacks permit remote control of
the BYPASS, INFINITE REPEAT, and VCO functions.
The Lexicon A-FS-41 Dual Footswitch Assembly may
be used to contro! the first two functions, and a Lexicon
A-CP-41 Foot Pedal for VCO control: or any of a
number of common foot switches or controls may be
substituted. You can also construct your own controller
according to the information provided below.
BYPASS SWITCH JACK (Fig. 2.2, C)
In BYPASS mode, two things happen: the delayed
audio is cut out of the MAIN OUTPUT MIX, and the in-
put to the delay line is interrupted. The BYPASS jack
accepts a standard 1/4” tip/sleeve (mono) phone plug,
and is activated either by a switch closure which
grounds the tip to the sleeve, or by a low-going (logic
“OOP TEL aera Opening the connection (or inputting a
logic ‘1’')'will turn off the BYPASS mode; we recom-
mend a latching footswitch for this function
INFINITE REPEAT SWITCH JACK (Fig. 2.2, D)
The REPEAT function allows permanent retention of
any sound stored in the delay memory. The REPEAT
jack accepts a standard 1/4” tip/sieeve phone plug; the
feature is activated either by a momentary switch
closure which grounds the tip to the sleeve, or by a low-
1
going TTL pulse. This mode ts cancelled by any subse-
quent momentary switch closure or pulse. Unlike
BYPASS, INFINITE REPEAT mode may also be con-
trolled from the front panel.
VCO REMOTE JACK (Fig. 2.2, B)
The VCO jack allows remote operation of the delay
sweep. It serves the same purpose as the front panel
MANUAL VCO- SWEEP control. idee a standard 1/4”
T/R/S phone plug is inserted in this jack, the front
panel MANUAL VCO-SWEEP ee is switched out
and the remote control is substituted. This function can
be controlled either by a potentiometer or by an external
voltage source with a range of 0 to +10 volts.
lf a potentiometer is used, it should have a linear
(rather than log or audio) taper. Values of 10k to 500k
ohms will work; 50k is preferred. The CCW end of the
potentiometer should be connected to the sleeve ter-
minal of the VCO jack, the CW end to the ring terminal,
and the wiper to the tip terminal. The remote control
will then function exactly as the MANUAL VCO-
SWEEP control does (i.e. CCW = X.5, CW = X2).
Voltage programming of the VCO function requires a
source with a range of 0 to + 10 volts, which could be a

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12

SECTION FOUR
APPLICATIONS
4.0 INTERCONNECTING THE PCM 42
amples shown below are representative of typical per
former, Studio and sound reinforcement setups. Front
Within a given sound system, there are a number of panel control settings to achieve specific effects are
possible patch configurations for using the 42. The ex-
given in Section 4.4.
SOURCE
FERGIE oe oe .
CRE SNS aun os : :
: : co Ca ges:
O oO : oe
ads eRe ‘
Sake Roos PS comer FSi
REA. Seserue a oe
O O db ss
Figure 4.1 — BASIC MONO SETUP
The setup shown in Fig. 4.1 is the most basic form of
connection for a performer. If other effects/processing
devices are used, the 42 delay line should be the last
item in the chain before the amplifier. See Section 4.5
for special types of interconnect to external devices.
PREAMP OUT
Figure 4.2 — BASIC SETUP WITH AMPLIFIER EFFECTS LOOP
Many modern instrument amplifiers provide preampili-
fier send and return jacks. If such a facility is available
on your amp, it is recommended that the PCM 42 be
connected into that loop. This puts the amplifier’s tone
controls and distortion effects ahead of the delay line,
generally giving a cleaner, more pleasing effect.
13

SOURCE
Figure 4.3 —~ BASIC STEREO SETUP
only in stereo, e€.g. mono-to-stereo conversion and
localization of sound image. We highly recommend the
use of the stereo setup in Fig. 4.3, or a more general
setup using a mixing console (See Fig. 4.4).
Many of the very striking effects achievable with
audio delay require a stereo field for maximum impact.
These include ambient enhancements, double tracking,
ben ey t
slap echo and others. A few applications are possible
SOURCE 1
SOURC
ae
/?
MAIN
&
>
|
CEES MONITOR
AMP
OUTPUTS
— Si | sp
L@
i
—
EFFECTS RETURN
SOURCE N
Figure 4.4 — BASIC RECORDING OR SOUND REINFORCEMENT SETUP
review the definition of each effect. |f you are com-
pletely-familiar with the common usages of time delay,
the illustrations and their captions will be all you need.
Readers who would like to learn more about time delay
applications than is presented here may send for a copy
4.1 GENERAL APPLICATION NOTES AND of Lexicon Application Note AN-3.
SET-UPS
For sound reinforcement and studio applications, the
PCM 42 is usually connected to an effects send and
return on the console.
In trying out these settings, consider the fact that for
4.1.0 Introduction any given setup the audible effect may be completely
different for different program sources. For example,
some tunneling effects may be dramatic with vocals and
in the course of showing you how to create specific
scarcely noticeable with guitar. For this reason, the
delay processing effects with your PCM 42, we will
14

patch diagrams are intended enly as suggested starting
points. By a means experiment and derive your own
favorite effect
In the following front pane! drawings, darkened but-
tons are engaged foiessed in}. Control settings are
marked on the knobs ex cae where the setting does not
alter the basic effect (e.g., wherever VCO DEPTH is at
“O" the WAVEFORM sit RATE settings are
4.1.1 Echo
irrelevant). Input level is not shown as this must be set
up for the specific source in use. For setups that use
sweeping delay times, the numbers indicated in the
display window are to be set up with the DEPTH control
set at ‘0’; then DEPTH should be raised to the level i:
dicated for that effect. Generally speaking, the Belay
times shown need not be precisely emulated to achieve
the desired effect, and the longer the delay time in-
volved, the less critical the setting.
DEPTH WENEF ORM RATE
lexicon
oe digitat
pati delay
PPOCESSOr
‘ "Le
VCO. SWEEP
Figure 4.5-a — SLAP ECHO
This set-up adds rhythmic interest by doubling the attacks, and tonal interest by doubling the sustains. Sending the
output through a fuzztone circurt will produce a more dramatic distortion.
This mode simulates an acoustic echo, in which
sound bouncing off a hard surface is heard as a distinct
repetition of the original. The level of delayed sound
relative to direct sound gives the ear information about
the hardness and size of the reflecting surface. Natural
echoes have losses in the upper frequencies due to air
absorption: it may be desirable to use the DLY X2 push-
CELAT KZ
LEVEL FEEOBACK FUTER
button with its 6 KHZ rolloff when simulating a distant
echo even when the delay time is within the limit im-
posed by full-bandwidth operation. An external equal-
izer may also be inserted between the delay and the out-
put mix using the MIX CONTROL jack (See Section 4.4,
“Interfacing to Other Units’'). Delay times of 75 to 100
ms create what is commonly known as ‘‘slap echo”
DEPTH WAVEFORM.
Figure 4.5-b — AMBIENT ECHO
These settings simulate echoes from a medium-sized hard room. The reverb time will be a function of the FEEDBACK
setting. The proper amount of VCO modulation varies with the material, and can be quite high with a pure vocal track.
Ambient echo effects simulate sound reflections from
room surfaces. In true reverberation there are many ran-
dom reflections, a gradual decay of overail level, anda
gradual narrowing of bandwidth. While the PCM 42
only simulates reverberation with its ambient echo ef-
fects, there are situations where the results are
reasonably convincing and quite desirable.
lf the reflected sound continues to bounce back and
forth between surfaces, it provides a long decaying
+5
“tail’’. To produce this effect, use 30 to 150 ms of delay,
in conjunction with some recirculation. Experiment with
the H! CUT filter and the FB INV function to simulate
the absorption characteristics of different reflecting sur-
faces. To further enhance diffusion of the echoes, try
very small amounts of VCO modulation at slow rates.
With musical programs that have few sharp attacks, the
ambient echo cdn closely resemble true reverberation.

CLETRALE DAE
FEEDEACK
PHTER BELMSE
—
@
HPL
SELAODE
00K
o
&
digital
delay
PIOCeSSOF
% Leith
DELAY VCO-SWEEP
Figure 4.5-c — MULTI-ECHO
More obvious echoes and less ambient effect than with the settings of Fig. 4.5-b. For more repeats, increase the
FEEDBACK: for more prominent echoes, advance OUTPUT MIX.
INPUT
VCCE SWEEP
Figure 4.5-d — LONG ECHO
For layering effects, the delayed outputs should be made equal to the direct sound by centering the OUTPUT MIX. In-
creasing the FEEDBACK will increase the number of layers. These settings only begin to show the layering of which
the PCM 42 is capable; see Section 4.2 for further information.
Longer delay times provide a more distinct repetition
of the source. The PCM 42 has 2400 milliseconds of
delay time available in standard configuration, and up to
4800 milliseconds with the memory aption. This cor-
responds to a reflecting surface a half a mile away!
4.1.2 Double Tracking
ORLAY X2 LEVEL FEEDBACK, PUTER
OE tener OE
fo B wL_ 253:
Figure 4.5-e — DOUBLE TRACKING
Doubling is most effective in stereo; feed one channel from the DIRECT output, the other from the MAIN output, and
turn the OUTPUT MIX all the way to DELAY. (See Fig. 4.3.)
Doubling, also called automatic double tracking or
chorusing, combines original and delayed sound in
order to make a single performer sound like two or
more. Doubling was originally done with a multitrack
tape recorder by having a performer overdub a perfor-
mance on two or more tracks; when the takes are com-
bined, normal pitch and timing variations between the
“identical” performances provide enhancement and
thickening. The PCM 42 can of course provide doubling
during a live performance — something not practical
with tape recorded effects.
Doubling provides the most convincing effect in
stereo mode: use the DIRECT and MAIN outputs to
feed different tape tracks, console inputs or
amplifier/speaker systems, as in Fig. 4.3. If the effect is
Recirculating the delayed signal with the FEEDBACK
control provides multiple repeats, suggesting an echo-
canyon effect. Large amounts of feedback give an ar-
tificial ‘infinite layering’ effect at long delays. (See
Section 4.2.)
MANUAL DEPTH WAWEFORM RATE
4 xicon
ene digital
delay
processor
16
‘
& 1 wi kity a OF
4 xe
VCO. SWEEP
done in mono, the amount of delayed sound should not
exceed the amount of direct sound in the output mix:
set the OUTPUT MIX control between “INPUT” and
“= Delay times in the range of 10 to 60 ms are useful.
A small amount of VCO modulation should be used: set
WAVEFORM to “SINE or mix ENVELOPE
FOLLOWER and SINE, then bring DEPTH up very
slowly until there is a noticeable vibrato in the output.
Back off again until the vibrato subsides to a subtle
enhancement, then adjust RATE for the desired effect.
Short doubling times, coupled with some feedback
and somewhat exaggerated sweep provide the ‘rotary
speaker’ effect, which is more exaggerated than simple
doubling.

4.1.3 Flanging
CEL AY BD LEVEt FEEDBACS. FUSER
WAVE CM
xicon
cdigitad
POwEth
: delay
& @ PROCESSOF
2
VCO. SWEEP
Figure 4.5-f — FLANGING
The delay should be set initially with the DEPTH control fully counterclockwise. This effect will be most pronounced
on sound with rich harmonic content — those with reedy timbres or cornplex chords. Possible variations include
changing FB INV, FEEDBACK, and all VCO-SWEEP controls.
Th 7
This effect is known as a
5 produced by
The classic sweeping
ecording the same proc
ah
a
gram ape recorders and
mixing their output while jews m alternately. In be further al tere ed by recir-
effect, a short delay time (1 - 20 ms) is mixed with the back to the input. ere
direct signal and the delay time is varied continuously. or fee ack. cause exag-
nges. Phase inversion of the feed-
This causes cancellations of narrow frequency bands, eg]
called nulls, to sweep across the various components of back signal gives a characteristic ‘“hollow’’ sound.
the program input. Different harmonics are boosted or
cut in relation to each ather, causing the tone of the in- Use of the envelope follower me odula tion Source on
put to change in a characteristic Way: the PCM 42 produces an interesting “talking flange’;
sweep fs produced for each ae of the ee
A variation occurs if the polarity of the delayed signal Envelope and sine wave Sweep can be combined for a
is inverted with respect to the input signal. This causes complex sweep. Square wave modulation may be used
the nulls to fall only at the odd multiples of the fun- to create an unusual effect.
4.1.4 Resonant Effects
ORLAY <2 LEVEE FEEDBACK FRTER PHASE OUTPUT Mak SET. MODE DELAY res DEPTH. WAVER CRA Rm EE
= t
ERY steer OTK
VCO-SWEEP
Figure 4.5-g — RESONANCE
A pipe-y single-note resonance whose frequency may be varied in steps (with the delay time pushbuttons) or con-
tinuously (with the MANUAL VCO-SWEEP control).
SET-MODE OePTH basen best RATE
6 w a a ER
Figure 4.5-h — TALKING RESONANCE
A resonance that varies with signal level. Be sure to adjust the input LEVEL control for full modulation; moderate
overload will be taken care of by the PCM 42’s soft clipping circuits. (Severe clipping will still produce some unwanted
side effects.)
OELAY 82 LEVER FEEDBACK. PUTER
eo. Sree
Singing in the shower is one way to obtain a natural, are affected by the delay time, the amount of feedback
moderate resonant effect. Using the PCM 42 at short used, and the status of the HI-CUT and FB INV
delay times with large amounts of feedback causes pushbuttons. Turning FEEDBACK all the way up and
buildup of fundamental notes and harmonics whose the setting OUTPUT MIX on DELAY, with a delay time
period is equal to the set delay time. The effect is to add of about 12 ms, will create the “Cylon” voice of TV
a ringing, metallic quality to the sound, especially with fame.
percussive inputs. The pitch and tone of the resonance

4.1.5 Vibrato
PATER
FEEDBACK
alice.
ciepttal
delay
processor
veo. weer
Figure 4.5-i — VIBRATO
The DEPTH and RATE of the vibrato are controlled with the corresponding VCO-SWEEP controls. Setting the VCO
WAVEFORM clockwise produces an interesting ‘‘trill’” effect.
mye r
Vibrato ts the effect produced by small, regular varia- mY JT MIX all the way clockwise. Inflections can also be
tions in pitch. The PCM 42 can create a automatic vibrato ontroiled manually by the MANUAL VCO-SWEEP
for any instrument or sound. The DEPTH knob controls control, or by an external foot controller connected to
e oe of the vibrato, the RATE the VCO jack.
Use short delays with no feed ack
controls the speed.
, af nd turn the OUT-
4.1.6 Pitch Twisting
ORLAY X27 REVEL FREOB ACK. FREER Set — RAADELIAL CErrH WAAR ER Cott BATE
= : a
lexicon
Cry ax Ey
Te ck digital
L { og : POWER pe
o@ OF bite ) IYOCESS OF
E
Figure 4.5-; — PITCH TWISTING
Radically altered swept pitches completely transform any instrument into something totally alien. For less extreme ef-
fects, turn down the DEPTH control.
When an audio delay line is modulated, as by the
VCO-SWEEP section of the PCM 42, a transient shift in
pitch occurs that is proportional to the rate of change in
rapid sine wave can produce some very unusual
sounds, indeed.
delay time. The effect is analogous to the acoustic ef-
fect known as Doppler shift. The use of larger amounts
of sweep at longer delay times produces exaggerated
bends in pitch which can be used for very odd special
effects. With the settings shown in the figure, the shift
follows the waveform of the modulation. The amount of
shift for a given setting of DEPTH increases with the
amount of delay selected by pushbuttons. The use of
waveforms such as envelope follower, square wave or
4.1.7 Stereo image Placement
DELAY £2 LEVEL FEEDBACK FREER
&
00660
ZOOS Ow mT
g
The VCO control jack on the rear pane! may be used
to inject any synthesizer waveform into the unit, pro-
vided the range of the waveform is 0 to +10 volts.
Many unique effects can be produced using common
synthesizer functions such as sample-and-hold, se-
quencer, pitch follower, envelope generator, or audio
oscillator. Pitch Twisting may also be controlled
manually by the MANUAL VCO SWEEP knob or by the
use of a foot pedal plugged into the VCO jack.
haat RATE
ei lexicon
POWER Pi gd
processor
vase SWEEP
Figure 4.5-k — STEREO IMAGE PLACEMENT
Delaying the right output causes the sound source to shift to the left. Adjust the delay between about 6 and 30 ms to
achieve the desired degree of shift.

The prevalent technique for placing the image of a
source within a stereo sound field is to pan the signal
from left to right, relying on the amplitude difference
between the channels to create the perceived image
position. But certain advantages can be realized by
using delay in conjunction with, or even in place of,
conventional panning. Imaging by means of level differ-
ences alone works well only for listeners located mid-
way between the two loudspeakers; at off-axis loca-
tions, the image shifts toward the loudspeaker from
which the sound arrives first, a psychoacoustic
phenomenon known as the Haas effect.
The Haas effect arises from the brain’s ability to iden-
tify similarities between sounds arriving at the ears at
different times. Any sound sufficiently similar to one
which arrived at the ears within the previous 30 milli-
seconds will be perceived as a reflection of the original,
and the brain will localize the source as coming from the
direction of the first arrival. The greater the delay be-
tween the two arrivals, the more the source’s apparent
location shifts toward the first one.
The Haas effect can be transformed from a problem
into an asset by using it in a controlled way to shift the
apparent position of a sound source in the stereo field.
With the PCM 42 connected in the Basic Stereo Setup
as shown in Fig. 4.3, simply adjust the delay to achieve
the desired degree of apparent offset of the sound
source. Delaying the sound in the right channel will
cause the source to shift to the left, and vice versa.
Delay times of 5-30 ms are most useful; above 30 ms,
the delayed sound begins to be perceived as a separate
echo, destroying the effect. (For additional information
4.2.1 Layering and the Infinite Repeat Mode
DELAY XZ LEWER FEEOGACK FUER
SET MODE
OL me CLK
ot = OF cox
O rgd
“y %
on this subject, consult Lexicon Application Notes AN-2
and AN-3.)}
4.2 SPECIAL APPLICATIONS OF LONG
DELAY
4.2.0 Introduction
The class of musical applications for long delay
{greater than one second) is somewhat distinct from the
applications discussed above. These are closely akin to
results obtained with tape loops, but the special quali-
ties of digital delay and the unique features of the PCM
42 allow much greater freedom than is attainable with
tape, even without the PCM 42's obvious advantages
over a couple of high-quality open-reel recorders in
compactness, ruggedness and cost. Many techniques
previously confined to home or studio can now be used
in live performance.
In general terms, the use of very long delays in music
produces a type of ‘canon’ or polyphonic effect by
superimposing the audio image of previously performed
phrases over current material. With no feedback, only
one previous phrase will be audible, but if feedback is
added, each delay period will repeat more than once
before it dies away. With large amounts of feedback,
the performance will pile up, one phrase over another,
until input to the delay line ceases or the unit is placed
into the infinite repeat mode. At full feedback and max-
imum delay time (with the optional memory extension)
the decay time of the PCM 42 exceeds 3 minutes!
PARAL GEPTH WAVEFORM
RY
DELAY
Figure 4.5-| — CANON
This option begins to make use of the multilayering potential of the PCM 42. The delay time should be set at the max-
imum available; for machines with the memory option, the MANUAL VCO-SWEEP control will be at about 10:30
o'clock.
Using this overlay technique, it is possible to create
compositions and rhythmic beds in real time that can be
trapped via infinite repeat, or continuously evolved by
adding new notes as older ones are tading out. When
the repeat function is used, the resulting backgrounds
may be soloed over without entering the notes into the
delay loop.
19
itis important to be aware of the nature of the Infinite
Repeat function in the PCM 42 in order to make full
usage of the looping technique. WHEN THE INFINITE
REPEAT MODE iS ACTIVATED, THE FULL MEMORY
IS ALWAYS UTILIZED. The length of the segment cap-
tured in memory is independent of the delay tap
selected by the UP and DOWN pushbuttons. It is af-

bee ONLY by the setting of the VCO-SWEEP controls
d the DLY X? pushbutton.
OF GH ¢
down aunt ei eeu se}
in Ths section.
nae: icatio
bey
ae
working with long loops, the delay ta
synchronized to the period of the infinite re
2. 10 ene total length of the availabie memory.
ng procedure will achieve this:
DELAY TO THE MAXIMU!
Press the UP pushbu
) while ae ing DOWN _In about 5s
lay will “top out” at the m maximum delay Hime for
the present amare rate. Now release the two bu
(DOWN first, then UP; otherwise the setting will back
up one or two steps from maximum). The segment
length is now exactly equal to the delay time as
displayed on the front panel.
i 9 oS
DIME
ae
in
gown
+h 4 ~
the disp
2.) ADJUST THE MANUAL VCO-SWEEP CONTROL
TO AN EVEN VALUE OF DELAY. If your PCM 42 has
no memory option, a value of 800 will occur near the
center of the control’s travel: with the memory option,
the value will be 1600.
4.2.2 Looping Techniques for Live Performance
CHELAY X2 LEVEL FEEDGACK PUTER
60 BE
SEE MODE
aie
CG
TO
400.
(8
800
aires:
200
(400
with
memory
wi th
PisveOry
option):
for
fou
option},
and
so
os
On.
4.) ADJUST THE MANUAL V
POR THE DESIRED avis
and the length of the
chronized, you may ¢
the MANUAL
echoes will
rate is
CO-SWEEP CONTROL
Now that the delay time
NITE REPEAT loop are syn-
ae both together by adjusting
VCO-SWEEP control. The decaying
remain in synchronization as the sampling
varied.
A very useful technique with the infinite repeat is to
get a basic line or part trapped into the memory, then
turn feedback up full clockwise. When the infinite
repeat is released, the looped segment does not die
away immediately, but continues to repeat Gue to the
high degree of regeneration used. (Be sure you have set
the segment length as described above.) While in this
state, new notes, rhythms, or lines may be added over
the old. Then if the unit is placed once more into repeat
mode, both the old and new parts will be heard. This
technique would not be feasible except for the superior
qualities of Lexicon’s special encoding circuitry, which
contribute very little audio degradation to a recirculated
signal.
OEPTH WAVER CRM
sy ee —
eveos
cue
Ue hie
wos
EHEBOLOTeLe)
Figure 4.5-m — LONG DELAY LOOP
This is a more extended form of the setup in Fig. 4.5-1, with many layers. Sound can be captured in INFINITE REPEAT
mode; when this mode is turned off, new layers can be added to the sound and the composite put back in INFINITE
REPEAT. For instructions on how to synchronize the beginning of the measure to the beginning of the repeat cycle,
see below.
Once the procedure described in Section 4.2.1 has
been carried out, the delay times will be synchronized
with the length of the INFINITE REPEAT loop. There re-
main two potential barriers to the maximally effective
20
use of this facility: how to synchronize the beginning of
a measure with the start time of the loop, and how to
establish tempo within a repeated loop that is too long
to count reliably