Pacific Recorders & Engineering Corporation LSM-10 User manual
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0.
PACIFIC
RECORDERS
&
ENGINEERING
CORPORATION
-
---------+------------
I
THE
LSM-1O
LINE
SELECTOR
MODULE
FEATURES:
■
10
SELECTABLE STEREO
INPUTS
■
MAIN AND AUXILIARY
OUTPUTS
PLUS
3
RECORDING OUTPUTS
■
STEREO GAIN RANGE CONTROLS
■
SELECTABLE
INPUT/
OUTPUT METERING
■
SELECTABLE MONITORING OFMAIN OUTPUTAND 3 TAPE
RETURNS
■
INDEPENDENT MONITOR WITH LEVEL CONTROL
■
RECORD/PLAY-
BACK FEEDBACK LOCKOUT
T
he
LSM-10
Li
ne
Selector M
odule
allows production,
newsroom
and
recording personnel
to
selectanyof10
li
ne
-
l
eve
l signal sour
ces
(i
ncluding
thr
ee
t
ape
machines)
fo
r
mon
it
oring,
mete
ri
ng
and
recording. This ster
eo
unit
is
base
d
upon
a program amplifier
preceded
by
a source-
selector
swit<::h
, to which montoring
and
metering circuitry
has
been
added.
Th
e program
amp
l
ifier
output
is
routedto
a se
ri
esofconnectors
on
t
he
r
ear
of
theuni
t:
a
ma
in output,
an
auxiliary
ou
tput
and
a
se
t of
ou
tpu
ts
to
three
ta
pe
recorders. T
he
sour
ce
-selectorswitch
is
con
fi
guredso th
at
whena t
ape
machine is selected
as
the source,the output
line to t
hat
tape
reco
r
der
is
int
errupted,
pr
eventing
the
possibility
of
f
eed
b
ack
. The program
amp
li
fie
r
has
a
front-
panel
ga
in
-t
rim
contro
l.
T
he
mon
it
oring ampli
fi
er,
wi
th h
eadphone
-driving
capa
-
b
ility,
allows mon
it
or
ing
of
the
output of
any
of
t
he
t
hree
t
ape
machines
oroft
he
program
amplifier, all
indepe
n-
den
t
of
the sour
ce
-selector switch. T
he
monitoring
ampli
fi
er
gain
is adjust
able
wi
th a front-
panel
level
con
t-
ro
l.
It
s
outpu
t
appears
at
the
front-
pane
l
head
-
phone
jackwhich
is
normalled-throu
gh
to a rear-
pane
l
connec
-
tor,
fo
r possible
app
li
cation to
an
ex
t
ernal
power
amp
lifi
er.
T
he
VU
m
ete
rs
are
driven
by
buffer
amp
lifi
ers
and
qre
fr
ont-
panel
switch
ab
le to a
ll
ow level
measurement
/
of
eitherthe selectedsource or the program amplifier output.
LS-4
·
an:d
LS-10
LINE
SWITCHERS
LS-4
LS-10
Also
available
are
two
passive
switching systems. The LS-4
is
a
set
of
four 4-input by ]-outputstereo switches. T
he
inputs
are
all isolated; a total
of
sixteen inputs
can
be
accommodated. The
LS
-
10
is
a pair
of
JO
-input by ]-output stereo switches.
Th
e inputs are connected
in
parallel on the LS-10.
LSM-10 Functional Block Diagrmn
MET
ER
INPUT
OUTPUT
INPUT1
$2
$7
'----
~
AUX.
OU
T.
SB
A
TAPEINPUT1
o--
-
--+-O
-----------
-------
-
-------~
S8B TAPEOUT 1
TAP
EIN
PUT2
o-------+--o
S9A S9B
- -
--
- - - - -
--<>+--+0----
--
- -
----0
TAPE OUT 2
S10A
TAP
EI
NPUT3
o-----+--+-o
S1
0B
- - - -
----
-+--o+-.C>--------
--'--
---o
TAPEO
U
T3
INTERLOC
KS
IMO
NI
TO
R I
OUTPUT NOTES:
1.
Left
C
hann
el
on
ly
is
show
~
TAPE1
2.~Cont
r
ol
TAPE2 3.
Po
wer
supply
not
shown
TA
PE
3
'------o
MONITOR OUT.
4.
Wilen
a
Tape
Input
is
cho
S8f\
t
l'e
corres
pon-
ding
T
ape
Out
put
lin
e
is
opened
• -- ---'-
______
L_S_
M-
_ l_0_TE_ C_
HNI
_ C_AL
__
SP
_E_C_
IFI
_ C_A_
TI
_O_N_S_·
_______
----/
Nominal Input
Signal
Levels
:
Ga
in Adjustment &
Range
:
Source
Impedance
:
·'input
Impedance
:
Common-mode
Rejection:
Output Level:
+ 4
to
+ 8
dBu;
see
notes
- 2 to + 24
dB
600
ohms or les
s,
ba
l
anced
or
unbalanced
Program amplifier: 50K ohms line-to-
line,
balanced,
instrumentationinput
amplifiers
Monitor Amplifier:
as
above
Metering Amplifier: 60K ohms
Program Amplifier: better
than
50
dB
,
20
Hz
to 20
kHz
(60
dB
typical)
Monitor Amplifier: better
tha
n
40
dB,
20
Hz
to 20
kHz
(55
dB
typical)
Program
Amplifier:
+ 8 dBu nominal;
clip point
is
+ 29 dBm into 600 ohm
load
Monitor
Amplifier:
+ 8 dBu nominal;
clip point
is
+
21
d~hm
load /
Output Source
Impedance
:
Output
Load
Impedance
:
Frequency
Response
:
Signal to
Noise
Ratio:
Harmonic Distortion:
Intermodulation Distortion:
Crosstalk:
Power Requirements:
Size: 19" wide, 3.5"
hi
gh, 10''
deep
Weight: 10
pounds
; 20
pounds
domestic
shipping
~1
003,
Pacific Recorders & Engineering Corporation
I. These specifications
are
subject to
change
without prior notice.
Program Amplifier: Less
than
100
ohms,
balanced,
floating, transformer-
coupled
Monitor Amplifier: Less
than
40
ohms
unbalanced
600 ohms or
greater
+0, -0.6
dB,
20
Hz
to 20
kHz
Better
than
90
dB with + 8 dBu test
tone, 20
Hz
to
30
kHz
bandwid
th
Program Amplifier: better than 0.01%
at + 29 dBm into 600 ohm load,
1
kHz
; better than 0.03% at + 29 dBm
into 600 ohm load, 50
Hz
to
20
kHz
;
Monitor
Amplifier:
less than 0.01%
at +
21
dBm into 600 ohm load,
20
1-lz
to 20
kHz
Less than 0.005%, + 8
to
+ 29 dBm
in
to 600 ohm load,
SMPTE
(60/7000
Hz)
Better
than
85
dB,
20
Hz
to 20 kHz
120 VAC,
50/60
Hz
,
10
watts
2.
0 dBu corresponds to
an
amplitude
of
0.775 V
RMS
regardless
of
impedance.
It
is
the
same
as
0 dBm
if
the
i
mpedance
of
the circuit
under
discussion
is
600ohms
.
It
may
be
consklered
0 dBm (enabling convenient
measurement
with meters
calibrated
for
a
600
ohm circu
it)
if
the
circuit
impedance
is
simply
disregarded.
3. The program amplifier
and
me
tering amplifiers in the LSM-IO
have
ad
justable gain,
enabling
operations on either
+4
dBu
or
+ 8 dBu systems.
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Ta
b
1e
o f Co
at
e
nt
a
1.
Introduction
2.
Specifications
3.
Warranty
4.
Installation
4. 1 Unpacking
4.2
location
4.3
Input
Connections
4.4
Output
Connections
4.5
Power
Connections
4.6
Meter
Zero
5.
Operation
5
.1
Introd
u
ction
5.2
Non
-Tape
Inputs
5.3 Tape
Inputs
5.4
Monitoring
5.5
Metering
6.
Technical
Description
6.1 Program
Amplifier
6.2
Monitoring
Amplifier
6.3
Metering
Amplifier
6.4
Po
w
er
Supply
7. Drawings
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1.
lllTK.OD0CT1Ofil
The
LSM-10
Line
Selector
Module
allows
production,
newsroom
and
recording
personnel
to
select
any
of
10
line-l
evel
signal
sources
(including
three
t
ape
machines)
for
m:>nitor-
ing,
metering
and r
ecording
.
This
stereo
unit
i s
based
upon a
program
amplifier
preceded
by a
source-selector
switch,
to
which
mnitoring
and
metering
circuitry
has
been
added
. The
program
amplifier
output
is
rout
ed
to
a
series
of
connectors
on
th
e
rear
of
the
unit:
a
main
output,
an
auxiliary
output
and a
set
of
outputs
to
three
tape
re-
corders.
The
source-selector
switch
is
configured
so
that
when a
tape
machine
is
selected
as
the
source
,
the
output
l
ine
to
that
tape
recorder
is
interrupted,
preventing
the
possibility
of
feedback.
The
program
amplifier
has
a
front-panel
gain
-
trim
control
.
The
mnitoring
amplifier,
with
headphone-driving
capabil-
ity,
allows
oonitoring
of
the
output
of
any
of
the
three
tape
machines
or
of
the
program
amplifier,
all
independent
of
the
source
-
selector
switch.
The
mo
nitoring
amplifier
level
is
adjustable
with
a
front-panel
level
control.
Its
output
appears
at
the
front-panel
head-phone
jack
which
is
normalled-through
to
a
rear-panel
connector,
for
possible
application
to
an
externa
l power
amplifier.
The
VU
meters
are
driven
by b
uffer
amplif
i ers and
are
front
-p
anel
switchable
to
allow
level
measurement
of
ei
th
er
the
selected
source
or
the
program
amplif
i
er
output.
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2.
SPBCIFICATIOBS
Nominal
Input
Signal
Level
+4
to
+8 dBu;
see
notes
Gain
Adjustment
Range
-2
to
+
24
dB
Source
Impedance 600
ohms
or
less,
balanced
or
unbalanced
Input
Imp
edance
Program
amplifier:
50K
ohms
line-to
-
line,
balanced,
instr
u
tnentatioo
i
nput
amplifiers
Monitor
amplifier:
as
above
Common-mode
Rejection
Output
Level
Output
Source
Impedance
Metering
amplifier:
60K
ohms
Program
amplifier
:
better
than
50 dB, 20
Hz
to
20
kHz
( 60
dB
typical);
Monitor
amplifier:
better
than
40 dB, 20
Hz
t o
20
kHz
(55
dB
typical)
Program
amplifier:
+8 dBu
nominal;
clip
point
is
+29
dBm
into
600
ohm
load;
Monitor
amplifier:
+8 dBu
nominal;
clip
point
is
+21
dBm
into
600
ohm
load
Program
amplifie
r :
less
than
100 ohms,
balanced,
floating.
transformer-coupled
Monitor
amplifier:
less
than
40 ohms,
unbalanced
Output
Load Impedance 600 ohms
or
greater
Frequency
Response
+o,
-0.6
dB, 20
Hz
to
20
kHz
Signal
to Noise
Ratio
Better
than
90
dB
with
+8 dBu
test
tone,
20
Hz
to
30
kHz
bandwidth
Harmonic
Distortion
Program
amplifier:
better
than
0.005%
at
+29
dBm
into
600
ohm
load,
1 kHz; b
etter
than
0.
05%
at
+29
dBm
into
600
ohm
load,
50
Hz
to
20 kHz;
Monitor
ampli
fier:
less
than
0.006%
at
+21
dBm
into
600
ohm
load,
20
Hz
to 20 kHz
Intermodulation
Distortion
less
than
O. 005%, +8
to
+29
dBm
into
600
ohm
load
,
~PTE
(60/7000
Hz)
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Power
Requirements
Size
Weight
Notes:
120
VAC,
50/60
Hz,
10
watt
s
19"
wide,
1.75"
high,
10"
deep
10
pounds;
20 pounds
domestic
shipping
1.
These
specifications
are
subject
to
change
with
out
prior
notice
.
2.
0 dBu
corresponds
to
an
amplitude
of
0
.775
V
RMS
regardless
of
impedance.
It
is
th
e same
as
O
dBm
if
the
impedance
of
the
circuit
under
discussion
is
600
ohms.
It
may
be
considered
O
dBm
(enabling
convenient
measurement
with
meters
ca
librated
for
a
600
ohm
circuit)
if
the
circuit
impedance
is
simply
disregarded.
3.
The
program
amplifier
and
metering
amplifiers
in
the
LSM-10
have
adjustable
gain,
enabling
operation
on
either
+4
dBu
or
+8
dBu
systems.
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3.
WAi.R.ANTY
A)
Except
as
expressly
excluded
hereinafter,
Pacific
Recorders
and
Engineering
Corporation
("Seller")
warrants
equipment
of
its
own
manufacture
against
faulty
workmanship
or
the
use
of
defective
materials
for
a
period
of
one
(1)
year
from
date
of
shipment
to
Buyer.
The
liability
of
Seller
under
this
warranty
is
limited
to
replacing,
repairing
or
issuing
credit
(at
Seller's
discretion)
for
any
equipment,
providing
that
(I)
Seller
is
promptly
notified
in
writing
within
five
(5)
days
upon
discovery
of
such
defects
by
Buyer,
(II)
Seller
's
examination
of
such
equipment
shall
disclose
to
its
satisfaction
that
such
defe
cts
existed
at
the
ti
me
shipment
was made by
Seller,
and
(III)
Buyer
returns
the
defective
equip-
ment
to
Seller
' s
place
of
business,
packaging
and
tra
nspo
rtag
e
prepaid,
with
r
eturn
packaging
and
transportage
guaranteed.
B) Equipment
furnished
by
Seller
but
manufactured
by
another
shall
be
warranted
only
t o
the
extent
provided
by
the
other
manufacturer.
C) The
warranty
period
on
equipment
or
parts
repaired
or
replaced
under
warranty
shall
expire
upon
the
expiration
of
the
period
of
the
original
w
arranty.
D)
This
warranty
is
void
for
equipment
which
has
been
subject
to
abuse,
improper
installation,
improper
application,
improper
or
omitted
maintenance,
alteration
,
accident,
negligence
in
use,
stora
ge
,
transportation
or
handling,
operation
not
in
ac
co
rdance
with
Seller's
operation
and
service
instructi
ons,
or
operation
outside
the
environmental
conditions
specified
by
Seller.
E)
This
warranty
1s
the
only
warranty
made
by
Seller,
and
is
in
lieu
of
all
other
warranties,
including
merchantability
and
fitness
for
a
particular
pu
rp
ose
,
whether
expressed
or
implied,
except
as
to
title
and
to
the
expressed
specifications
contained
in
this
manual.
Seller's
sole
liability
for
any
equipmen
t
failure
or
any
breach
of
this
warranty
is
as
set
forth
in
subparagraph
(A)
above;
and
seller
shall
not
be
liable
or
re
sponsib
le
for
any
business
loss
or
interruption,
or
any
other
consequential
damages
of
any
nature
wh
atsoever,
resulting
from
a
ny
equipment
failure
or
breach
of
this
warranty.
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4 . UJSt'ALLATION
4.1
Unpacking
The LSM-10
should
be
carefully
unpacked
and
inspected
for
any
shipping
damage.
Keep
all
packing
material
in
case
a
claim
is
t o be made
against
th
e
carrier
for
damages.
Should
the
inspection
reveal
any
damage,
immediately
file
a
claim
with
the
carrier
.
Remove
the
top
cover
and
check
tha
t
the
various
plug-in
components
are
seated
and
that
no
comp
onen
ts
have
bee
n
shocked
out
of
place
in
ship
-
ping.
The
top
cover
should
then
be
re-installed
.
If
it
is
considered
likely
tht
the
VU
meters
will
be
re-calibrated,
then
the
cover
can
be
left
off
temporarily.
There
are
no
other
adjustments
which
might
be
made.
4.
2
location
The
LSM-1
0
occupies
two
rack
-
units
of
height
(3.5")
and
should
be
installed
in
a
rack
or
between
rails
which
have
been
grounded,
if
that
option
exists.
The
unit
should
be
located
at
the
operator's
position
in
the
recordin
g
or
pr
oduction
facility.
The
VU
meters
should
be
clearly
visible
and
the
source-selector
switch
should
be
co
nveniently
close.
4.3
Input
Connections
The
input
signals
applied
to
the
LSM-10
should
be
applied
from
a
sou
rce
of
600
ohms
or
less.
The
level
should
be
about
+8 dBu,
although
some-
what
low
er l
evels
are
useable.
The
circuitry
presented
to
the
source
will
be
a
set
of
instrumentation
amplifiers~
the
program
amplifier
presents
a
line-to-line
load
of
SOK
ohms;
the
monitor
amplifier,
when
it
is
monitoring
the
input,
presents
an
additional
load
of
SOK
ohms, and
the
metering
amplifier
, when
switched
to
measure
the
input,
presents
an
additional
load
of
60K ohms. These
figures
can
all
be
considered
bridgin
g
(no-load)
to
a
source
of
600
ohms
or
less.
All
co
nnection
s
to
and
from
the
unit
should
be
mad
e
with
two-conductor
shielded
cable
.
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All
of
the
inp
ut
connectors
have
the
following
format:
Pin:
Name:
1
left
Shield
2
left
(Low)
0l~J"
0
3
left
( High)
000
4
Right
Shield
5
Right
(Low)
View
of
Molex~
connec
tor
as
6
Right
(High)
seen
from o
utside
of
equipment
4.4
Output
Connections
The o
utput
signal
from
the
program
amplifier
in
the
LSM-10
will
normally
be
at
+8 dBu. The
internal
impedance
seen
looking
back
into
the
program
amplifier
is
about
100 ohms;
the
load
should
be
600 ohms
or
higher.
The
program
amplifier
output
is
transformer-coupled
and
floating
.
The
output
signal
from
the
m:>nitor
amplifier
is
continuously
adjustable
in
level
up
to
a
maximum
of
+21
dBm
into
a 600
ohm
load.
The
internal
impedance
seen
looking
back
into
the
avnitor
amplifier
is
about
40 ohms;
the
load
should
be
600
ohms
or
higher
. The
monitor
amplifier
output
is
unbalanced
and
appears
at
the
front
-
panel
headphone
jack
. Should
this
jack
be
unused,
then
that
output
signal
is
normalled
thr
ough
to
the
monitor
output
connector
on
the
rear
of
the
unit,
for
application
to
an
external
power
amplifier
and l o
udspeaker(s
) .
Both
of
the
XLR
-
type
output
connectors
have
the
following
format :
Pin:
Name:
l
Shield
2
Low
3 High
All
of
the
Molex
-
output
connec
tors
have
the
following
fo
rmat:
Pin:
Name:
1
left
Shield
2
left
(Low)
3
Left
(High)
4
Right
Shield
5
Right
(Low)
6
Right
(High)
www.SteamPoweredRadio.Com
4.5
Power
Connections
Th
e
un
it
requires
approximately
10
watts
of
power
at
120
VAC,
50
or
60
Hz, from a power
connector
w
hich
has
an
integral
ground
lea
d.
The
"third
pin"
on
the
power
connector
s h
ould
be
left
intact.
For
safety
re
asons,
this
pin
is
connecte
d
to
the
chassis
of
the
LSM-10
directly.
D:>
not
sever
this
pin,
do
not
sever
t
he
gr
een
wire
in
the
power
cord
at
either
end
and do
not
use
an
adap
tor
to
enable
the
three
-
prong
connector
to
plug
into
an
olde
r
-style
two-prong
o
utl
et
.
4.6
Meter
Zero
Prior
to
actually
applying
power,
check
th
e
VU
meter
me
chanical
zero
adjustments.
If
necessary,
zero
the
meters
with
the
aid
of
a
small
sc
rewdriver
.
www.SteamPoweredRadio.Com
5.
0PllliTI0B
5.1
Introduction
The
LSM-10
was d
esigned
to
enable
the
selection
,
ioonitoring
and
measure-
ment
of
a
set
of
signal
sources
in
an
envi
ronment
such
as
a newsroom
or
production
or
recording
facility
.
One
of
these
signal
sources
is
chosen
and
i s
rout
ed
t o a
program
ampl
ifier
.
The
output
of
that
program
amplifier
is
routed
to
a
pair
of
output
connectors
as
well
as
to
the
inputs
of
as
many
as
three
tape
re
c
orders
.
The
monitoring
system
cau
select
either
the
output
of
the
program
amplifier
or
the
playback
outp
ut
of
one
of
three
t
ape
ma
c
hines.
The
m
onitoring
switch
operates
independently
of
the
source
-
selector
switch.
The
monitoring
amplifier
is
designed
to
drive
headphones
or
an
external
power
amp
lifi
er.
The
meterin
g
system
can
measure
either
the
ac
tual
level
of
the
selected
signal
or
th
e
level
of
the
program
amplifier
output
.
(The
pro
gram
amplifi
er
has
a
front-panel
gain
-
trim
adjustment
whi
ch
allows
as
much
as
25
dB
of
ga
in
t o
be
added
to
the
input
signa
l.
)
5. 2 Non-Tape
lo
puts
The
LSM-1
0 accommo
dates
a
total
of
ten
inputs;
three
of
these
are
s
et
aside
specifically
(but
not
exclusively)
for
tape
-r
eco
rd
er
application
and
are
handled
internally
in
a
manner
sl
i
ghtly
different
from
the
remainin
g
(non-tape)
inputs.
The
non-tape
inputs,
which
might
be,
for
example,
from
a
net
work
feed,
a
two-way
rad
io
re
ceiver,
or
some
other
remote
source,
are
se
lected
by
the
INPUT
swi
tch.*
Whichever
so
ur
ce
is
selected
drives
the
pr
ogram
ampli-
fier.
Sho
uld
the
signal
be
lower
than
normal
lin
e
level,
its
amplitude
can
be
increased
by
usin
g
the
f
ront-panel
GAIN
control
. The
selected
signal
will
appear
simultaneously
at
the
main
and
the
auxiliary
output
co
nn
ectors
and
at
each
of
the
tape
output
connectors.
The l e
vel
of
the
chosen
input
signa
l
can
be
measured
by
operating
the
METER
switch
to
INPUT;
the
leve
l
of
the
signal
after
going
th
rough
the
pr
ogram
amplifier
can
be
measured
by
operating
the
METER
switch
to
OUTPUT.
* -
In
this
manual,
front-panel
con
trol
s
are
indicated
in
CAPITAL
S
www.SteamPoweredRadio.Com
The
non-tape
signals
are
best
mnitored
by
operating
the
MONITOR
switch
t o
OUTPUT.
5. 3 Tape
Inputs
Three
of
the ten
input
sources
are
reserved
primarily
for
the
us
e
of
tape
recorders.
These
may
be
reel-to-reel,
cassette
or
cartridge
types.
The
tape
sources
are
handled
in
a manner
similar
to
the
other
sources
with
th
ese
exceptions:
1.
When
a
specific
tape
machine
is
selected
as
the
source,
the
output
drive
from
the
program
amplifier
to
that
tape
machine's
recording
input
is
interrupted.
This
is
done
to
prevent
feedback.
2. The
monitor
system
can
be
switched
to
m:>nitor a
tape
machine's
output
directly,
prior
to
the
input
source-selecto
r
switch.
This
allows
the
operator
to
compare
tape
input
with
tape
output.
Which
tape
input
is
selected
is
determined
by
the
INPUT
switch.
The
selected
source
drives
th
e program
amplifier.
Should
its
level
be
low,
it
can
be
increased
by
operating
the
GAIN
control.
The
selected
signal
will
appear
simultaneously
at
the
main
output
connector
and
at
th
e
auxiliary
output
connector.
In
addition,
it
will
appear
at
the
inputs
to th
e
other
two
tape
machines,
us
efu
l
for
dubbing.
The
tape
signa
ls
can
be
DX>nitored by
operating
the
M
ONITOR
switch
to
OUTPUT
or
they
can
be
mnitored
by
operating
that
switch
to
the
appro-
priate
TAPE
(1,
2
or
3)
position.
The
TAPE
positions
can
be
us
ed
to
monitor
a
specific
tape
machine
at
any
time,
even
though
it
is
not
selected
as
the
signal
source,
because
the
mnitoring
connections
are
ahead
of
the
source-selector
switch.
The
level
of
the
chosen
tape
signal
can
be
measured
by
operating
the
METER
switch
to
INPtIT;
the
level
of
the
signal
after
going
through
the
program
amplifier
can
be
measured
by
operating
the
METER
switch
to
OUTPUT
.
www.SteamPoweredRadio.Com
5.
4
Monitor
1ng
The
monitoring
S)'Stem
in
the
LSM-
10
is
intended
to
drive
eithe
r a
pair-
of
headphones,
600
ohms
or
greater,
or
an
exter
n
al
power ampli f i
er.
The
volume
of
the
monitor
signal
is
continuously
a
djustable
using
the
LEVEL
control
up
t o a maximum l
evel
of
+21
dBm
into
a
600
ohm
load.
Head
-
phones
may
be
pl
ugged
into
the
front
-
panel
MONITOR
HEADPHONE
connector
on
the
LSM-10.
When
they
are
not
pl
ugged
in
t o
this
connector,
t
he
monitor
signa
l
is
routed
to
t
he
r
ea
r-p
an
el
m
on
it
or
out
put
connector
.
The
monito
r
ing
system
will
most commonly be
used
to
monitor
the
output
of
the
LSM-10, by
operating
t
he
MONITOR
switch
to
OUTPUT.
However, a
tape
may
be
played
and
monitored
by
operating
the
MONITOR
switch
to
the
approp
r
iate
TAPE
position.
In
this
manner,
a
tape
can
be
cued
up
or
confirmed
as
being
the
proper
tape
prior
t o
using
it
as
a
program
source.
5.5
Metering
The
metering
system
in
the
LSM-10
includes
b
uffer
amplifiers
so
that
the
meter
rectifiers
do
not
add
distortion
to
the
audio
signals
. The
meters
can
be
switched
by
using
t he
METER
switch
to
read
either
the
chosen
input
signal
leve
l
or
the
outpu
t
of
t
he
program
amplifier
.
6 . T
EC
HNI
CAL
DESCRIPTION
In
the
following
discussions,
it
may
be
helpful
to
refer
to
the
Block
Diagram
(Figure
1)
and
the
schematic
drawings
of
the
Program
Amplifier
(Fi.gure
2),
the
Monitor
Amplifier
(Figure
3)
,
and
the
Metering
Amplifier
and Power
Supply
(Figure
4)
. The
input
source
switching
is
shown
in
Figure
5
and
the
monitor
and
meter
switching
are
shown
in
Figure
6.
6.1
Program
Amplifier
The
program
amplifier
is
of
a
dual
configu
r
ation
fo
r
stereo.
Only
the
l
eft
channel
will
be
discussed,
and
the
component
designations
given
are
for
that
channel.
The
designations
of
components
for
the
right
channel
are
the
same
except
that
they
are
numbered
start
ing
at
101 r
ather
than
at
1•
www.SteamPoweredRadio.Com
The
source
as
selected
by
the
INPUT
selector
switch
is
applied
to
the
input
differential
amplifier
using
both
halves
of
Ul
. Rl
and
RS,
with
C2
and
C3,
provide
RF
bypassing.
Cl
and
C4
remove
any
DC
component
which
may
be.
present
on
the
input
line.
R3
and
R4
provide
signal
attenuation
balanced
to
ground.
The
input
amplifier
bas
its
gain
set
by
feedback
resistors
R7
and
RlS
operating
in
conjunction
with
the
series
string
of
RS,
R9
(the
gain
-
trim
pot)
and
RlO.
The
output
of
this
first
stage
is
applied
to
a
subtractor
using
ampli-
fier
U2. Gain and common-mode
rejection
are
determined
by
the
ratios
of
resistor
pairs
Rll
/ Rl2
and
Rl4
/ R20.
Ql
and
Q2
provide
current
amplification
for
U2
. The
remaining
components
around
this
stage
are
for
biasin
g,
temperature
stabilization
and
transient
protection.
The
output
of
this
stage
is
applied
to
the
primary
of
output
trans
former
Tl.
This
quad-filar
transformer
has
three
of
its
windings
connected
in
series-aiding
t o
provide
a
voltage
stepup.
The
transform
er
is
wired
to
both
the
main
and
the
auxiliary
output
connectors.
6.2
Monitor
Amplifier
The
monitor
amplifier
is
a
dual
type
for
ste
reo
. Only
the
left
channel
will
be
discussed.
The si
gnal
to
be
monitored,
as
selected
by
the
MONITOR
selector
s
witch
,
is
applied
to
an
input
differential
amplifier
using
both
halves
of
U3.
R21
and
R25,
with
Cl9
and
C20,
provide
RF
bypassin
g.
Cl8
and
C2
1 remove
any
DC
component
from
the
applied
signal.
This
stage
has
its
gain
set
by
feedback
resistors
R27
and
R33,
with
the
series
st
rin
g
of
R28
and
R29.
The
output
of
this
first
stage
is
applied
to
a
subtractor
us
in
g U4.
Gain
and
common-mode
rejection
are
determined
by
R30 /
R31
and
R34
/
R35. The
output
of
U4
is
applied
to
the
monitor
volume
control.
The
signal
set
by
the
volume
control
is
applied
to
the
output
amplifi
er
using
US
and
associated
components.
As
with
the
program
amplifier,
Q3
and
Q4
provide
current
amplification
and
the
remaining
components
provide
bia
sing,
stabilization
and
transi
ent
prote
c
tion.
The
output
of
thi
s
stage
is
applied
via
C42
to
the
headphone
ja
ck
.
This
jack
is
normalled-through
to
the
rear
-
panel
monitor
output
connector.
6. 3
Metering
Amplifier
The m
eter
ing
amplifier
is
a
dual
circuit
for
stereo.
Only
the
l
eft
c
hannel
will
be
discussed
.
www.SteamPoweredRadio.Com
R47
and R48,
with
C43
and C44,
provide
RF
bypassing.
Any
residual
DC
signals
are
removed
by
C45
and
C46,
with
RSO
and R51. The
amplifier
has
its
gain
set
by
feedback
resistors
R52
and R55,
operating
with
the
R54
and
R53
(
the
meter
calibration
control)
. The
amplifier
output
is
coupled
to
the
VU
meter
by
C52
and C53.
The
amplifier
has
a
very
low
output
impedance;
the
source
as
seen
by
the
VU
meter
is
resistor
R53.
Diodes
DSl
and
DS2
provide
overload
protection
to
the
meter
.
6.4
Power
Supply
Th
e
LSM-10
can
be
operated
from
either
120
or
from 240
VAC,
at
either
50
or
60
Hz
.
Operation
from 120
VAC
is
accomplished
by
connecting
the
power
transformer
primaries
in
parallel,
while
operation
from 240
VAC
is
accomplished
by
connecting
the
primaries
in
series.
Refer
to
Fi
gure 4
for
the
connections
.
The
transformer
output
is
rectified
by
full
-wave
re
ct
ifier
BRl
and
is
used
to
charge
primary
filter
capacitors
C54
and
C58
. The
voltages
on
these
capacitors
are
regulated
to
+15
volts
by
U7
and
to
-15
volts
by
US.
The
remaining
components
around
th
ese
regulators
are
for
overload
and
failure
protection
and
transient
response
improvement.
www.SteamPoweredRadio.Com
INPUT
INPUT1
INPUT2
o------o
I
I
I
I
INPUT?
o------o
TAPEINPUT1
TAPE
INPUT2
S1
S2
S7
SBA
S9A
S10A
METER
INPUT
OUTPUT
MAIN OUTPUT
AUX.OUT.
-----------~-~~~-------------~
S88
TAPEOLIIT1
S98
----------~-~~~-------------~
TAPE
OUT
2
S108
TAPE
INPUT3
o--
- - - - - - - -
~.,__-,(').,lll-tl-0------------------o
TAPE
OUT
3
INTERLOCKS
OUTPUT
TAPE1
TAPE2
TAPE3
I
MONITOR
I
LEVEL
MONITOR
HEADPHONE
p
-----~
MONITO
I
OUT
.
NOTES:
1.
Left
Channel
only
is
shown
.
2. I
PANEL
I
Control
3.
Power
supply
not
shown
4.
When
a
Tape
Input
is
chosen,
the
correspon-
ding
Tape
Output
Line
is
opened
FIG 1
LSM-1
O FUNCTIONAL
BLOCK
DIAGRAM
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