McMartin MX-5 User manual
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MC
Martin.
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MCMarti
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MX-5
I MIXER/
PREAMPLIFIER
I 1NSTRUCTION
MANUAL
I Index
page
I.
TECHNICAL
SPECIFICATION
S 1
I
11.
GENERAL
DESCRIPTION
1
Ill.
INSTALLATION
2
I
IV.
CIRCUIT
DESCRIPTION
2
V.
MAINTENANCE
3
I
VI.
PARTS
LIST
4
WARRANTY 5
l
VII
.
SCHEMATIC
DIAGRAM
6
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MCMartin.
I.
TECHNICAL
SPECIFICATIONS
INPUTS
Microphone .
....
.
Program
.......
.
INPUT
IMPEDANCES
Mic Channels
....
.....
Four
(4)
T
otal:
Channel
/11
switchable
to
operate
as
1
kHz
tone generator. Channels
113
and
114
convertible
to
RI
AA
equalized
magnetic phono
ser-
vice,
by
Internal
plug
reversal
..••.
..
. . .
..
.
....
........
One
..
50-1
50
ohms balanced; may be
modified
to
25K-ohms
unbal-
anced
by
in
ternal
strapping.
Channels
/13
and
114
swi
t
chable
to
47K-ohms
for
magnetic phono
se
r
vice
by
Internal
plug
reversal
Program Chann
el..
.
.600
ohms, balanced (ma
tching
)
10K-ohms. balanced
(b
ridging
);
or
25K-ohms, unbalanced,
(bridging)
INPUT
LEVELS
Mic Channell
....
.
....
~O
dBV
balanced: -28
dBV
overload
point
:
-55
dBV
.
unbalanced. Channels 3
&
4
in
magnetic phono mode:
2
ml
llivolts@
1 kHz
Program Channel. . ..
600 ohms matching
or
100 mlI-
ll
volts,
25K-ohms, unbalanced
FREQUEN
CY
RESPONSE
M
ic
Channels
....
.
±1.0,dB,
50-20,000
Hz.±
2.0
dB,
20-20,000
Hz;
or
-10
dB
roll-off
@SO
Hz by Internal plug reversal.
Ch
a
nnels
113
&
11
4
in
magnetic
phono mode:
within
2.0
dB
of
RIAA
cu
rve
Program Channel. . .
••
.....
±0.
5
dB,
50-20,000
Hz
;
± 1
.0
dB,
20-20,000
Hz
NOISE
2/ 77
Mic Channels.
...
.
..
65
dB
(wide
band) and
72
dB
1
wIth
15 kHz low pass
filter)
belo
w
+8
dBm output,
with
3.0
mV Input
signal.
Equiva-
lent
Input
N
oise:
-122
dBm.
Channels
113
&
11
4
in
magnetic
phono mode: -55
dB
Program
Channel. . .
..
.
80
dB
(
wide
band) and
85
dB
(W
/15
kHz
LP
filter)
belo
w
+18
dBm
output
OUTPUT
IMPEDANCE
S
&
LEVELS
..
.
.....
.
TOTAL
HARMONIC
&
INTERMODULATION
DISTORTION
.
.....
.
FRONT
PANEL
CONTROLS
..
.....
.
FRONT
PANEL
SWITCHES
.........
.
REAR
PANEL
A)
600 ohms balanced:
+4
or+8
dBm, nominal: + 18 dBm maxi-
mum
into
600-<ihm
load
8)
SK-0hms, unbalanced
t,3.0
volts,
rms
C)
50/150
balanced: -45 dBm
0)
Headphone Jack:
600
ohms,
unbalanced
(isola
ted)
t
+12
dBm
.....
0.5"ii
or
less.
20-20,000
Hz
@+8
dBm output
level
:
1.0%
or
less.
20-20,000
Hz
@
+18d8m
out
put
level
...
. Mic
111/tone generator
level,
M
ic
112
level,
M
ic
113
&
/14/equallzed phono
levels,
Program
leve
l.
and
Ma
ster
gain
...•
+ 4
or+8
dBm metering end
po
wer
on/off
SWITCHES
.......
.
..
. .
......
M
ic
/11/Tone Generator
REAR
PANEL
TERMINATIONS
....
. .
..
Channel
111
to
/14
Inputs, C1
F
POWER
connectors;
Mic
Level
Output,
C
1M
connector; Balanced
pro-
gram Input andbalanced 600-ohm
output, screw term
in
als
; unbal-
anced program
Input
and SK
-Ohm
unbalanced output,
RCA
phono
Jack:
36-volt
de external power,
two-pin
Cinch
Jones
socket
REQUIREMENT
S.
...
.
.105-
125 Vac,
50/60
Hz,
3
watt
s.
DIMENSIONS
......•
SHIPPING
WEIGHT
..•.
..
..•.
-
FINISH
......
.
•.
.
•.
(Fuse:
1/8
ampere,
slo
w-blow
):
or
36
Vdc,
70
mA
....•...
12
-3/
4"
(32.4 cm) wide
2-3/4"
(7
.0
cm) height
7-3/4"
(19.7 cm) deep
...•...........•
...
..
6 pounds
...
McMartin
blue
and
sliver
gray
II.
GENERAL
DESCRIPTION
The McMartin
MX-5
mhter/preampllller
is
an extremely
versa
ti
le
unit
designed f
or
Individual
level control and
signal
processing or
five
sepa
rat
e input sources.
with
amplification
of these premixed sour
ces
to
line
level
output.
The
five
input
sources
ar
e
mixed
by front panel con
trol
s;
four
at
microphone
sign
al
level,
either
with 50-150 ohm
balanced
characteristics,
or
by
In
ternal
plug
reversal,
WI
th
25K-0hm unbalanced
configuration:
and the
fifth
at
program
level.
Two
of
the microphone-level channels ere con
vertible
to
RIAA-equalized
magnetic phono
service,
by reversal
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M CM
artin.
of
Internal
plugs.
The
fi
r
st
microphone channel may be
converted, by a rear panel
slide
switch,
to operate
as
a '1-kHz
sine-wave
to
ne
generat
or
lor
system
test
level
pre'i!djustment purposes.
The
four
microphone channel response
character
i
stics,
by
in
ternal pl
ug
reversal, may be
either
'
fl
at'
or
attenua-
ted
10
dB
at
50
Hertz.
Rear
chassis
XL
-
type
female connectors serve
as
the
Input
termination
f
or
each
of
the
four
micr
ophone-
level
channels.
The
program
input
channel
will
accept
either
a 25K-ohm
unbalanced source through a rear-panel RCA phono
jack,
or
alternatively
th
rough rear-chassis
scre
w terminals,
a 600-ohm
matching
input.
A
fr
ont
panel master
gain
control
permits overa
II
level
adjustment
of
the premixed
input
signals.
Balanced, 600-ohm output,
with
+18
dBm
level
capa-
bility,
appears on rear panel screw terminals.
Alterna
-
tively,
a separate SK-ohm unbalanced output
at
3.0
volts
rms
level,
is brought
out
to
a rear panel
RCA
phono
jack.
Output
level
Is
visually
monitored by an
illuminated
VU
meter,
calibrated
to
display
'zero
vu·
when
either
a
+8
dBm
or
+4
dBm
leve
l, by front panel
switch
select
ion,
appears
at
the balanced ou
tput
terminals.
In
addition,
a microphone level
outp
ut
is
terminated in
an
XL-type
male connector.
I
sola
ted headphone output,
at
+1
8 dBm
level
, appears
on a
sta
nda
rd¼"
r
ear
panel phone
jack.
AC
power
Is
controlled
by a front-panel
slide
switch.
The MX-5
may
be powered
fr
om an
external
36
-
volt
de
source
th
rough a rear-panel
de
pow
er
jack.
Finished
in McM
artin
blue
and
si
l
ver
gray, the MX
-5
is
designed
for
desk-top
or
shelf-mount operation.
Il
l.
INSTAL
LA
TION
After
unpacking the
unit
,
inspect
thoroughly
for
either
external
or
Internal damage. If
any
is
detected, immedi-
ately
n
otify
the
shipp
ing
carrier
and
advise
McMartin
of
said
action.
During
the
abOve
internal
inspection
where the top
cove
r
has been removed, changes
In
channel Impedances
or
·fun
ction
(as channel
113
or
/14
magnetic phono
service)
should
be
made by proper jumper pl
ug
orientation
(See
Dwg.
110005
19
).
I
nputs
to
the
four
microphone/mlcrophone-phono channels
are
terminated In
3-p
ln,
XL
-type female connect
ors.
A
balanced-line
600-0hm program Input may
be
attached
to
a screw-type rear-<:hassis terminal
strip,
using shielded
tw
o-<:onductor
cable,
with
the
shield
attached
to
the
'ground'
te
rm
inal.
Alternatively
if
an unbalanced,
hig
h-
impedance program source
Is
used,
this
connection is
made through an
RCA
phono
jack
located on the r
ear
panel,
with
the
associated
jumper
in
the
UNBA
L
posi
-
t
ion.
Ba
lanced, 600-ohm output appears on rear-panel screw
terminals. Interconnection
to
ex
tern
al
equipment should
be made
with
shielded
two-conductor
cable
with
the
shield
attached
to
the GND terminal
of
the output screw
terminals.
MX-5
output, at a nominal -40 dBm
level,
appe
ar
s on a
rear-<:has
sis
3-pin male,
XL
type connector. Unbalanced
high
-impedance
output
is
terminated on a rear-<:hassls,
RCA
phono
jack.
The
output may
be
monitored through a
reari)!lnel
head-
phone Jack.
This
provides
a+18
dBm level
at
600
ohms.
Although
headphones of 600-ohm
or
higher
impedance
are
recommended, usable
level
Is
availab
le for head-
phones
of
lower impedance.
The
four
low-
level
microphone input cnannels w
it
I
accept
balanced, 150-ohm microphones,
or
alternatively,
by
jumper-
plug
reversal (See Dwg.
110005
19) unbalanced
high
-impedance microphones. Channel 3 and 4 w
lll
also
accept
magnetic phono
inputs.
For
t
his
opera
tion.
th
e
ap
pr
opriate
MIC/PHONO
and
LO/H
I
Jumpe
r plugs should
be reversed.
High-impedance
or
magnet
ic
phono Inp
ut
connections
are made
to
pins
Ill
a
nd
113
(111
Is
ground) of the input
XL-<:onnectors.
An
internal
TONE
GEN
ERATO
R,
associated
with
the
MIC
Ill
Input is energized by opera
tion
of
the rear panel
TONE/MIC
sw
itc
h.
Th
e level
of
the tone is adj
usted
by
the
MIC
Il
l
mixer
control
for
se
tt
ing
system
levels.
IV. CIRCUIT DESCRIPTION
Mi
crophone input
signals
are
amplified
to
mixing
bus
level
by use of dual
amplifiers
loc
ated
in
IC-
1 and IC-2.
One
half
of
each
IC
Is
used
per
Input
channel, and
since
the operation
for
each
of
the microphone Inputs
Is
essentially
Ide
ntical,
except
f
or
input
/out
put
pin
desig-
nations
for
the
IC's,
the operation
of
MI
C 2
input
only
w
ill
be
desc
ribed.
Th
e balanced
input
s
ignal
is
fed
to
pins
2 and 3 of the
XL
Input connector, through T
·2
to
the input termina
l,
pin
8
of
IC-1B.
(C-7 provides
RF
fil
tering).
Not
e that
f
or
high
impedance
mic
rophone Inputs (pi
ns
1 & 3
of
input
connector),
T-2
ls
bypassed by reversi
ng
the'
HI
/
LO
jumper
plug.
The input
signal
path·
Is
then
directly
to
pin
8
of
IC-1B.
The frequency response
of
I
C-1
B may
be changed from
FLAT
to a -
10
dB
roll-off
curve by pla-
ci
ng
the
FLAT
/BASS
CUT
Jumper
plug
in
the
position
which
selects
the C-
11
, rather than the C-10,
capacitor.
These
capacitor
s,
in
conj
unction
with
A-a,
R-e
and R-10,
compr
ise
the proper feedback network
for
establ
is
hing
th
e frequency response
of
IC
-1B. Tne
output
of
IC
-1B,
pin
5,
is
fed to
MIC
2
mixer
control R-12, the ro
tor
of
whi
ch through
mixing
bu
s load r
esistor
R-13 feeds the
bus
input
to
the balance
of
the
circuitry.
The operation
of
MIC
-1
for
TONE GENERATOR opera-
tion
and MI
C--3
and MI
C-4
for
magnetic phono operation
are
slightly
di
ff
ere
nt
than the MIC-2 operation Just des-
cribed.
When
to
ne generation
is
desired, SW
-3
Is
placed In the
TO
NE
position.
Th
is
applies
oper
ating
voltage
to
the
tone
generator
circui
try
associa
ted w
ith
0-1
and
0-2.
pr
oduc
ing
a
sine
wave o
utput
signal
of
nominally 1000
Hertz.
Operation
of
SW
-3 in the TONE
position
also
switches
the
input
to
MIC-1
mixer
control,
R~.
fr
om
the output of
IC-1A
to
the output
of
the tone generator.
The magnetic phono
equalization
(w
ithi
n 2
dB
of
the
AIAA
curve) f
or
PHONO ope
rati
on
of
mixers
113
and
114
is
performed by
placing
the MI
C/P
HONO jumper plug
in
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MC
Mart
in.
the PHONO
position.
For
channel
113
(channel
1/4
is
ident
ical),
when the jumper pl
ug
is
in
the PHONO
posi-
tion
a feedba
ck
network
co
nsistin
g
of
R-16, R-17, R-18
and R-19 and
C-
14, C-15, C-16 and C-18
Is
inserted
between the
IC-2A
input
and
output
producing the
desired
RIAA
response
curve.
Note:
when channels
113
and/or
114
are operated
in
PHONO mode, the
associated
FLAT/
BASS
CUT
jumperplugs should
al
ways be
in
FLAT
posi
-
tion.
Balanced 600-ohm program input sources
at
a nominal
·10
dBm
level
may be fed
to
channel
/15,
thr
ough
connec-
tion to TB-1
A.
Th
is
input
is
transformer-isolated by
T-5
with
the Jumper
plug
in
the
BAL
position.
Bridging
bal-
anced Inputs
may
be
used by removing R-26 and R-38.
Unbalanced inputs are fed
into
a rear-panel RCA phono
jack.
T-5
is
bypassed
for
such inputs by
positioning
the
Jumper
plug
In the UN
BAL
po
si
t
ion
.
Balan
ce
d,
or
unbalanced program Inputs, feeds the PGM
mixer
control,
R-39.
The
mixer
bus (combination
of
mixer
channel
/11
through
#5
outputs)
is
fed
to
the R-50 MAS
TE
R
gain
control.
The
rotor
of
R-50 feeds the
inputs
of
IC-3.
One
section,
IC
-3
A,
of
this
dual
audio
in
t
eg
rated
circuit
drives
the
headphone
output
jack.
The rem
aini
ng
hal
f,
IC-3B,
ln
conjunc
tion
with
0-3,
provides a
high-level
unbalanced
low-impedance ou
tput
sig
nal
wh
ich
is
transformed
to
a
balanced, 600-ohm
output
by
T-2.
A separate unbalanced
5000
ohm
output
is
terminated on a rear-<:hassis RCA
phone
jack.
The
balanced
output
ls
visually
monitored
by the front panel VU meter, M-1, and
is
terminated
at
TB-1
B.
Line
levels
of
el
ther
+4
or
+a
dBm may be
moni-
tored by proper
switch
positi
on
of
SW-2.
In
addition,
this
output
is
attenuated by the network
of
R-4, 5 and 6
to
provide a nominal -40 dBm microphone
level
output
at
a rear-panel
3-pin
male
XL-
ty
pe conne
ctor.
The MX-5 cont
ain
s a de power supply,
with
on/off
ac
power
controlled
by POWER s
witch
SW-1.
LM
-1
provides
neon-lamp VU meter i
lluminatlon.
D-2 and D-3 provide
ful
l wave
center
tap rect
ific
at
ion
of
T-1 secondary
ac
voltage.
C-
43 Is the
filter
capacitor.
This
de
voltage
Is
regulated by
pass
transistor
O-4, referenced
to
a
Symptom
No VU meter I
llumlnation
Fuse fa
lls
when power applied
No+36
Vdc
at
power supply output (cathode ot D·1 )
No output
or
distorted
output
at
TB-1B, but headphOne
output okay
/7fi
36-vo
lt
Zener diode,
Z-
1, and the capacitance
multi
•
plie
r
effec
t
of
C-42. The M
X-5
may
also
be operated from
an
ex
ternal 36
volt
de sourc,
'.
capable
of
delivering
a
constant
load
of
70
milli
ampere
s.
1N4004 diodes
series-
connected
in
the internal and external de power
supply
feeds
isolate
the two power sources and prevent damage
from connection
of
an externaI de su
pply
of reverse
polarity.
V. M
AINTENANCE
Ma
intenance and repair of the
MX-
5 should
be
performed
only
by
qualified
service
personnel experienced
in
transistor/integrated
circuit
technology. McMart
in
Indus-
tries
maintains a
full-time
staff
qualified
to perform
this
type
of
service.
Factory
repair insures that
origi
nsI
equipment parts will be used rather than
similar-type
replacement components.
Before attempting repair, the f
ollo
wing preliminary
checks
should be made:
1.
Ascertain
that
power
is
actually
being applied
to
the
equipment. Check power source,
line
cord and plug,
fuse and
fr
ont
panel
ac
switch.
2.
Disconnect
external
lines
from
TB
-
1B
and
substitute
a 600-ohm
resis
t
or
.
If
the MX-5
Is
now operational.
the trouble
exists
in
the interconnecting
line
or
in
equipm
ent
external to the MX-5.
3.
Check
Input sources, microphone
cables
and conne
c-
tors. Interchange microphones between
mixing
chan-
nels.
If
one microphone
is
'dead',
logical
substi
tu
-
tions
will
help
in
Isolatin
g a defecti
ve
unit.
4.
Check
input
sw
itches
for
proper
positioning.
In
the event the above conditions are
satisfied,
it
may
be assumed
that
the
MX-
5
is
at
tau
It.
The following
fau
It
location
tabulation
wi
11
be
helpful
in
isolating
the problem and remedying same.
Cause
Check power
switch
SW-1
and fuse,
F-1.
Shorted primary winding
(T-1)
Shorted
rectifiers
(D-2, D-3)
Shorted
Ii
lter
capacitor (C-43)
Ground
short
on
positive
supply on main
PCB.
Open regulator
transistor,
0-4
Defec
tive
isola
ting diode, D-1,
Shorted Zener
diode,
Z-1
Shorted
Ii
l
ter
capacitor,
C-43
Open
rec
ti
lier,
D-2
or
D-3
Open power transform,Jr, T
-1
Defective
switch,
S
W-1
Open fuse, F-1
Output
li
ne shorted.
Defe
ctive
transistor,
Q-3
Detective
line
transformer, T-2
Defective
ou
tput
coupling
capacitor
, C-37.
'B'
section of IC-3
defective
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MCMartin.
4
Symptom
Output
level
okay
,
but
no
headphone
output
or
di
stor
t
ed
headphone
signal
One microphone channel 'dead'
or
distorted
Channels 1 & 2
bo
th
okay.
but Ch
annels
3 & 4
bo
th
'dead'
or
vice
versa
No signal through balanced program
input
Cause
"A"
section
of
IC-3
defec
t
ive.
capacitor
C-40
defective.
Check
HI
/LO
jumper
plug
for
proper p
osi
tion
Microphone may be de
fe
c
tive
Transfer
inpu
t
mic
plug
to
another channel
If
lhat
channel
okay,
micr
ophone
defective.
If
not,
check
input
transformer,
IC
: input and
output
co
upling
capa•
cl
tors.
Defective
IC
,
or
decoupling
RC netwo
rk
(C-8, R-
11
or
C-26, A-32) from
de
supply
Check
pin
/16
on
IC's.
Check po
si
tion
of
BALI\JNBAL
jumper
plug.
MUST
be
in
BAL
posi
tion.
VI.
PARTS LIST
The
majority
of
components used
in
the MX-5 are
of
standard values and tolerances and
are
generally
avail·
able
from locaI
electronics
parts
wholesa
l
ers
.
Those
or
unusual
value, tolerances
or
mechanical
configurat
ion
or
of McMartin manufacture
are
listed
below.
In
ordering
replacement
parts,
please
specify
model,
serial
number, McMartin
part
number and
description.
CHASSIS
PART
S
Symbol
0-1
F-1
LM-1
M
-1
R-5, A-12, A-22, A-33,
R-39, R-50
T-1
T-2
MAIN
PCB
PARTS
C-1, C-6, C-12,
C·21,
C-34, C-39
C-8, C-26, C-37
C-35
C-4
2,
C-43
0·
1,
0-2,
0-3
IC-1, IC-2,
IC-3
0-3
0 -4
A-45
T
-1
through 4
T·5
Z-
1
Part
Number
210008
280016
290013
700063
401019
900076
910046
600052
600011
600034
600013
210008
230062
201071
201024
410053
910060
910052
220008
Description
Diode,
type
1N4004
Fuse, .125 amp,
slo
-bto
Lamp, neon,
A9A.
11
0 V
M
eter,
VU
Control,
mixer
or
master;
50
K
-<ihm
C-1 taper
Transfonner,
powe
r
Trans
former.
line
output
Cepac1
tor,
electrolytic,
0.5
mfd/63
V
Capacitor,
electrolyt
i
c,
47
mfd/25
V
Capacitor,
electrolytic,
47
mfd/63
V
Capacitor.
elect
r
olytic.
100
mfd/6
3 V
Diode,
ty
pe
1N4004
Integrated
Circuit.
dual;
type
LM387N
Transistor,
type
MPS-UOS
Transistor.
type 2N3053
Trimmer,
resistor
: 2.SK-ohm
Transformer. microphone
input
Transformer, progr
am
input
Diode,
Zener;
36
volt
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I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
MC
Martin.
WA
R
RANT
Y
McMartinproducts are warranted
to
be free from defectsin materialsandworkman-
ship for a period
of
one year after shipping date. when subjected to normal usage
and service. All warranties are void
if
(a) equipmenthas beenaltered
or
repaired by
others without McMartin's specific prior authorization;
or
{b) equipment isoperated
under environmental conditions
or
circumstances other than those specifically
described in McMartin literature
or
instruction manuals.
Upon notification within the applicable warranty period. McMartin agrees without
charge, to repair. replace.
or
supply replacement parts for any properly maintained
equipment orparts that are defective as to design, materials
or
workmanship and
that are returned in accordance with McMartin's instructions
to
the Buyer.
At
McMartin's sole discretion, the Buyer
may
be requested
to
return the defective part
or
equipment
to
McMartin,
FOB
Omaha, Nebraska. Parts
or
equipment may be
returned only with McMartin'sprior authorization and must be identified by a return
authorization number previously issued by McMartin's Customer Service Depart-
ment. All merchandise
so
returned
must
be senttransportation prepaid, at Buyer's
risk. Full details
of
the failure
or
malfunction should be included
so
as to expedite
repair
or
replacement. Repair parts
or
repaired
or
replaced equipment will be re-
turned
to
the Buyer, FOB factory.
Theabovewarranty
does
not
extendtootherequipment,such
as
tubes.transistors.
I.C.'s lamps
or
fusesmanufactured byothers.whicharesubject
to
onlysuchadjust-
ment as McMartin may obtain from the suppliers thereof. McMartin shall not be
liableforconsequentialdamagesresulting from the use
of
,
or
the inabilityto use.the
equipment:
nor
for any loss. damage
or
expense incurred thereby:
nor
from any
other cause.
Except as set forth herein, and except as
to
title. there are no warranties,
or
any
affirmations
of
fact
or
promises by McMartin, with reference to the equipment, or
to
merchantability, fitness.
for
particularapplication, signalcoverage. infringement.
or
otherwise.whichextendbeyondthedescription
of
theequipmenton
the
facehereof.
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