Ampex 351 Series User manual

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DESCR fPTION AND PERFORMANCE CHA RA CTERSTICS
GENE RAL . . . . . . . . ..
PERFORMANCE ClIAR AC T ERSTICS .
EQU IP MENT AVAILAB LE
lNSTALLATION ,
GENERAL.
TNTERCONN£CT I NG
MOUNT I NG
POWER CONNECTION
OUTPUT
I NPUT
SUMMAR Y
Pl JONES
REMOTE CONTROL
60 CYCLE AMPLIFIER
OVER - ALL P~: HFORMANCE CII ECK
D IS TORT L ON .
FLUTTER AND WOW .
OPERAT I ON
GENERAL .
SUMMA HY OF CON THOLS , SW IT CHES AND I ND I CATO RS
OPERATING TEC ll Nl QUES .
T
II E DEVELOPMENT AND T H EORY OF MAGNGTlC TAPE R ECORDING
TII EORY Of MAGNET IC TAPE RECORD I NG . .
1-1
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2-1
2
-1
2-3
2-3
2-3
2-5
2 -5
2-5
2-5
2-5
2-6
2-6
3-1
3-1
3
-2
3-4
4-1
4-2

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,
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TAPE
rRANSPORT
MECIIANISM
.
GENEHAL
...
TAPE
SUPPLY
AND
TAKC-UP
SYSTEl\1S
TAPE
DRI
VE
SYSTEM
.
BRAKI:.
OPERAT
I
ON
CONTHOL
CIRCUIT
ROU
rJNE
MA
I
NTENANCE
ADJUSnIENTS
. . .
SPRING
SCA
LE
R
EAD
JN
C
PARTS
LIST
.
TAPE
THANSPORT
THE
AJ\ll'EX
II
EAD
IN[)JVfll
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HEAD
PARTS
ELECTHON
IC
ASSE!\IBLY
GEN
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RECOl{l)
MIPL
Jrl
EH
REPRODUCE
A
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AND
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PAl:TS
LIST
.
ELECTRONIC
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5-1
5- 1
5-1
5
-4
5-4
5-5
5-7
5-
10
5-1
1
5-15
6-1
6-4
7-1
7-1
7-3
7-4
7-5
7-5
7-6
7-6
7-12
7-12
7-
15
7-16
7-25

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AMPEX SER IES 351 RECORDER ; REPRODUCER -¾ VJF:W
RACK l..J\YOUT (
l\fODEL 351-2) . . . .
CENTER 'I AP GROUNDED BALANCED OUTPUT AND
STRAPPING FOR 4 VU OUTPUT . .
MICROPIIONES WITH 50 OI IMS OR LESS IMPEDANCE
Il[GII IMPEDANCE MI CROPHONE INPUT .
INT ERCONNECTING - S INGL E TRACK
lNTERCONNECTTNG , . , . , ,
TAPE TIIHEAOING PATH
VALDEMAR POULSEN
MAGNETIZATION UF TAPE
RECORD IIEAD . . .
RECORDING MEDIUM MAGNETIZATION CURVE.
REPRODUC8 IIEAD CIIARACTERS TJ CS
ACII I
EVING FLAT OVER -ALL RESPONSE
COMPONENT ANO ASSEMBLY CALLOUTS
TAPE TENSIONING
TAKE - UP AND REW I ND MOTOR ASSEMBLIES
CONTROi . CIRCUIT BOX . . .
DEMAGNETIZING TIIE HEADS
CONTROL cmcurr BOX CALLOUTS
CAPSTAN fOLER PRESSURE MEASUREMENT .
2-2
2-2
2-3
2-3
2-4
2-6
2-7
3-4
4-1
4-2
4-2
4-2
4-3
4-4
5-2
5-3
5-5
5-6
5-9
5-10
5-11

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BRAKE BAND REPLACEMENT_
REMOTE CONTROL
SCHEMATIC DIAGRA l \11 TAPE TRANSPORT CO 1 TROL
CIRCUlTS ( FOLDOUT SHEET )
SIMPLIFIED CONTROL CIRCUIT SCHEMAT IC
MODEL 351 TAPE TRANSPORT ( FOLDOUT SHEET )
HALF -T RACK IIEAD ASSEMBLY
FULL - TRACK 1IEAD ASSEMBLY
TWO-TRACI<
IIEAD ASSEMBLY
STANDARD 351 HEAD CONFIGURATIONS
LOCATION OF ELECTRONIC SUBASSEMBUES
AMPLIFIER CHASSIS, FRONT PANEL
AI\IPLIFIER CJIASSTS. REAR VIEW
BLOCK DIAGRAM.
RECORD CIRCUIT
BLOCK DIAGRAM,
REPRODUCE CIRCUIT
IIEAD AZIMUTII ADJUST IVIENT
SIGNAL-TO-NOI
SE RATIO COMPUTATIONS
MI CROPHONE RESPONSE SET-UP
SYSTEM BLOCK DIAGRAM
TROUBLESHOOTING TIIE REPRODUCE AMPLIFIER
TROUBLESHOOTING THE RECORD AMPLIFIER
APPLICABLE RESPONSE CUllV l•;S ( TWO FOLDOUT SHEETS )
PARTS LOCATION ( ETCllED BOARDS) ( ONE FOLDOUT SHEET )
SCHEMATIC DJAGR!\iv!S ( TllREE FOLDOUT SIIEETS ) _
5- 13
5- 14
6-1
6-2
6- 3
6-4
7-2
7 -2
7-3
7-3
7-4
7-9
7- 11
7- 12
7-
13
7-14
7- 14

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SECTION 1
ND PERFORMAt~CE
CHARACT RISTICS
GENERAL
The AMPEX Series 351 Magnetic Tap e Re-
cor der/ Reproducers arc high quality precisfon
instruments designed for th e professional us er
who requires the finest and mos t faithful r e-
cording and reproduction.
A basic recorder/reproducer in
the 351 ser ies
consists
of a tape tran spo rt for operat ion at
t ape speed pairs of 3¾ in ch es per second (ips)
and 7½ ips or 7½ and 15 ips; a h ea d assemb ly
for u
se with th e ¼- in ch magnetic tape; a nd an
electron
ic assembly which co ntains the record
amplifier. reproduce arnpUfier, bias
and e ras e
oscillator,
and power supply -all featuring
etc h ed board const ru c Uon .
NOTE
T/zis manual is primarily intended for
reco
rd ers using Ampex Catalog Num-
ber 30960 electronics. In instances
-where there are significant differences
between this elec tron ics assembly and
earlier models us in g Catalog Number
30750 or 30950 electronics an appro-
priate
notation will be fozmd.
H ead assemb li es for either full (si ngl e)
tra ck, half tra ck or two track stereo phonic
(351-2) operation are available.
CCIR e
quali zation can be obtained on request
1 -1

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when ordering equi pment.
Several mounting arrangements are offered
-c onsole, tw o case po rta ble, and rack mount.
In the portable equipment, one case contai ns
the tap e transport and th e other hou ses th e
electronic assembl
y.
Tap e Width
Tape Speed Pairs
Frequency Response
Signal-to-Noise Ratio
Flutter and Wow
Recording or
Reproducing Time
(NAB 1O½ In ch Diam eter
Reels, 2400 feet of tape)
Starting Time
Stopping Time
Reprodu ce Timing
Accuracy
Rewind Time
PE RF ORMANCE CHARACTERISTICS
¼-inch
3¾-7½ ips
7½-15 ips
Speed (ips)
3¾
7½
15
R esponse (Cycles per second)
+ 2 db 50 to 7,500
+2 db 40 to 10,000
-+-4 db 30 to 15,000
± 2 db 30 to 15,000
Speed (ips) P eah Record Level to
Unweighted Noise ( db )
3¾ 50
7½ 60 full track
55 h
alf track or two track
15
Same as 7½ ips
Peak reco td level is that level at which the overall (input to outp ut )
t
ota l rms h armo ni c di stortion do es not exceed 3 percent when
measured on a 400 cycle tone. Noise is m easure d when erasing
a signal of peak recor din g level in the absence of new signa l. Bias,
erase and r ep r od u ce amp lifi er noise are includ ed in the m eas ure -
ment. All frequencies between
50 and 15,000 cycles are m eas ured.
Speed (ips) Flutt er and Wow
(per cen tag e rms)
3¾ .25%
7½ .2 %
15 .1 5%
Flutter and wow measurements include all co mp onents between
0
and 300 cycles using an rms value of const ant amp li tude s in e
wave flutter.
Speed (ips)
3¾
7½
15
Half Track
(hrs) (min)
4 16
2 8
1 4
Full T rack
(hts) (m in )
2 8
I 4
32
The tape is accelerated to full speed in less than 1/ 10 of a second.
When operating at 15 ips, the tap e moves less than two inches
after the S TO P button is pressed.
Accuracy
( percentage )
±. 2%
Accuracy
(sec ond)
+ 3.6
Length of Re cording
(min)
30
Approximately 1 minute for a full 2,400foot NAB reel.
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Controls
Tnptt .l
Tape Motion
Record Control
Tap e Speed
Equalization
Reel Size
Record
Inpu ts
MICROPHONE
BAL BRIDGE
UNBAL BRIDGE
Reproduce Outpu.t
1-J cad H ousin_q
M011itorin.9
(aural and visual)
AH tape motion is controlled by fom' pu shb utton s, PLAY, STOP,
FAST FORWARD
and REWIND.
A separate RECORD butt on on the fac e of the electronic assembly,
wh en pressed, energizes the record relay which dr ops o ut wh en
the STOP bu tton is pre sse d. Th e stereophonicfunction (t wo u·ack)
is controlled by pressing
the RECORD buttons on both elec tt onic
ass emblies si mult aneousl y. Tn two track operation,for cons istency.
th e master electron ic assembly ls usually connected to the upp er
track
in th e h ead assembly so that , when the RECORD button
on the mast er (onI y) js press ed, recorcling takes plac e on the
upper track.
T
ape speed can be changed by the TAPE SPEED switch. LOW or
Hl GH positions arc used to se le ct drive motor windings.
An EQUALIZATION switch on the face of th e electronic assembly
provides a m
ea ns for se l ect in g LOW or HIGH speed equali za tion
appropriate to the tape speed used.
A R
EE L SfZE toggle switch on the tape tra n sport makes possible
se l ec tion of the prop er tape tension ing for the NAB 1 0½ in ch
diam eter reel or the E IA 5 in ch and 7 1nch reels.
The INPUT TRANSFER
SW I TC H provides a m ea ns for se lecting
th ree different types of inputs :
Input I mpedancc
150 and 250 oh ms n om inal
(t
ransformer can be strapped
for 30-50 o hm s nomin a l. )
200K o hm s
100K
ohms
Minimum h qmt Signal that
will produce Operating Level
(1 ~ lllp e characteri.i:;t'ic
di stortion)
150 mi crovolts
- 10 dbm
-10 dbm
Zero indication on the v-u meter corresponds to +8 dbm (+ 1 db).
Sufficient gain and power h
and ling capab ilities ex ist to feed a
+
14 vu line outpu t into GOO ohms balanc ed or unbalan ced. Th e
center tap of th e outp ut tr an sfor m er can be strapped to ground
fo r balanced outpu t. Plus 4 vu also can be obtained by strapping.
(See
IN STALLATION).
The e ras e, record, and re produ ce h ea ds are contained in a single
h
ead housin g (See SECTION 6 on HEAD ASSEMBLIES).
Th e signal on th e tap e can be monitor ed while the e quipm e nt is
record
in g. Two phone jacks are avail ab le to allow monitoring th e
r
ec ord input signal, or the o utput signal from the reproduce head.
A
sw it ch provides a means for makin g clir ect compari son between
th e ori gina l program an d the recorded program. Th e sa me switch
transfers a 4 i nc h vu meter for level comparison and visual
monitorin
g. Th e vu meter also is used to indi ca te bias a nd erase
curre nt.
1-3

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Power R equirements
Dimensions and Weight
(in.) (lb.)
Ra ck Mount.
Console
T
wo Case
Po rta ble
R emo te Control
The h alf track and s in gle track equi pm e nt requires 2.0 amperes
at 11 7 vo lts ac and is ava ilable for 50 or 60 cycle line frequency.
Two track equ ipment requires 2.5 am peres at 117 vo lt s ac, 50 or
60 cycles.
Wh en the Ampex Model 375 Precisi on Fr e quency 60 cycle ampli-
fier is used
with th e eq uipm ent, power req uir ements are greater
by 2.5 amperes: sing le t rac k eq uipm en t 4.5 a mp eres; dual track
5.0 a
mp eres.
EQUIPMENT AVAILABLE
I
tem
Heig ht Depth Wicll'h
Tap e Transport
15¾
8 19
(rac k space) (beh in d rack)
Electronic 7
8½
19
A
ssem bl y (
ra ck space) (behin d rack)
Con so le
48 ( max )
28½ ( max )
24½
Tap e Tran sport
15½. 17
20¼
Case ( Equipment
in Cas e)
El ec tronic Ass'y. 9
13
2)
Case (E quipm e nt
in Case)
Two Tra ck Stereo-
16 ½ 13 21
phonic Elec tr onic
Ass'y. Case (Equip-
me
nt in Case)
P art Numbers fOT Re mote Control unit s are located
in the Electronic S ec tion Parts List.
1-4
Weight
50
18
155
69
38
80

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NOTE
Before operating the equipment read
this SECTION AND SECT I ON 3,
OPERATION.
GENERAL
The 351 Series equ ipm e nt is shipped
mounted in conso l es or portabl e cases after
a thorough in spection and performance ch eck
at the factory. In the eve nt that the e quipm ent
is Tequcsted disassemb l ed, for customer rack
mountin g, a ll assembly h ardware is prov1dcd.
INTERCONNECTING
Sec the appropriate int ercon n ecting dia-
grams at the b ack of this section.
MOUNTING
Console Models
To assemble the conso le model proceed as
follows:
Step 1: J nstaJl the tape transport in the cab-
1net frame, securing the 8 oval-h ead
screws and finjshing washers.
Step 2: Place th e two springs in the hol es for
the c!cctrnnic assemb Jy cab ill ct frame.
Step 3: Attach the two rails to the electronic
assembly u sing the numb er 8 sc r ews .
Stl!J1 4: Sudc the cab in et back panel up and
out to allow c onnecting of the a-c
power cab Jc and plug the input cab le
a
nd the outp ut cab le into thciT recep-
tacles on tbe back of the elec troni c
2-1
SECTION 2
IN STA LL ATION

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A.mpex Series 35 1 Recorder / Reproducer - ¾ View
assembly.
Step 5: Jnsta l1 the electronic assemb l y, tight-
eni.ng the four knurled nuts to fasten
it to the frame.
Step 6: Connect the captive head ca bl es at
th cjr locations on the electronic as-
scm bl y.
Step 7: Connect the captive CABLE TO
ELECTRONICS to
the electronic as -
semb l y.
Step 8: Replace the back panel, making cer-
tain
that all cables run freely through
the semi -c ir cular cut-outs at the bot-
tom
of the sliding panel.
Two Case Por tabl e Mod els
(For 351-2 sec the applicable INT ERCON-
NECT ING illustration at the back of this SEC-
TION).
The two case portable models are s hipp ed
in a ready to operate conclition, except for the
connection of int erco nn ecting cab les. Conven-
ient rubber feet arc located at both ends of
each case , and metal rests arc provided on the
2-2
backs
of each case. To set up the equipment
follow these steps:
Step 1: Arrange the cases so that the mechan-
ical assembly case
is to the right of
the electronic assembly case.
Step 2: Unlatch and remove the top cover
and the side access door on the me-
chanical assembly case.
Step 3: Unlatch and .remove the front and
rear covers on the electronic assembly
case .
Step 4: Uncoil the interconnecting cables
from behind
the cable access door on
the tape transport case and plug them
into
mating receptacles at the rear
of the electronic assemb l y.
Step 5: Connect the a-c power, a nd the input
and output to the rear of the elec-
tronic assembly.
Ra ch layout ( Model 351-2)

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Rock Mount ed Models
Mount these versions of the equipment on
a standard 19-inch relay
rack with the mechan-
ical assembly above the
main electro ni c panel.
POWER CONNECTION
Connect the power cab le from the a-c
POWER input connector, J8 , on the electronic
assembly to a conveni
ent 115 volt a-c power
source.
OUTPUT
A mating connector for LINE OUTPUT is
supplkd.
The user must fabricate hjs own
cables, using the connectors supplied with the
recorder.
Studio Line
Plus 8 v-u, 600 ohm line output , bal anced
or unbalanced. is ava ilable across terminals 2
and 3 of the line out connector, J 5. Pin 1 is the
chassis ground.
If unbalanced output is desired, wire the
mating connector so that the pin 2 side of the
lineis tied to
ground or tieA to B at TSI. Supply
600
ohm t er mination to this output at all times
to
maintain cmTect meter calibration while
recording
or reproducing. If the ou tput is not
feeding a terminated line, or if the outp ut is not
connected, such as on r emote pickups, the line
out termination switch, S4, mu st be l eft in the
ON position.
+ 408 (O VU
~- 7
Center tap grounded balanced output and strapping
for 4VU output.
2-3
To obtain a ce nt er tap, grounded balanced
output, s trap the black le ad of transformer T3
to ground at the tie
point shown in the illustra-
tion.
Plus 4 v-u
output can be achieved by un -
strappjng D and E at transformer T3 and
strapping E to F. Re adjust the record calibra-
tion according the to instructions
in SEC-
TI
ON 7 ALIGNMENT AND PERFORMANCE
CIIECKS.
High Impedance Amplifier Input
Wire t he matin g connector so that pin 3 of
the li
ne out co nn ector, J5 is connected to the
high side of the amplifier input. Strap pins 1
a nd 2 of the mating connec t or for connection
to the grou
nd s id e of tbe am plifi er input. Th e
line
out termination switch S4, must be le ft
in the ON position at all tim es.
INPUT
Dur j ng this discussion refer to the foldout
illustration -Schematic Di
agra m-Electronic
As semblies at the back of SEC TI ON 7,
Microphone Input
Any low imp edance microphone hayjng a
nominal
imp eda nc e between 30 and 250 ohms
can be plugged directly fato the equ ipm en t.
Wire
the mating connec tor so that the mi cro-
phone is connected to
pins 2 and 3 of LINE
I
NPUT , Jl. The cab le shield mu st be connected
to
pin 1. Place the input transfer switch, Sl,
in the MIC position,
LI NE.
INPUT
s-1
INPUT TRANSFER
MICROPHONE SWITCH
BALAN CED ~'
J~-•-+- -- BR~IO(;E~--o! >-------v- - ,o -
RI ~~~o'olr ~O
621(
R~
47K
RZ. R3
22 Z.2
Microphones with 50 ohms or less imped ance.

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The microphone input transformer is
strappe d for the optimum step up when u sing
a 150 to 250 ohm source. With microphon es
of 50 ohms or less imp edance , to obtain 6 db
additional gain strap the input as shown.
This should be don e only if insufficient gain
is found to exist when the input is fed from
a source impedanc e l ess th an 50 ohms.
J-1
IMPORTANT
To maintain flat response in th e
balanced bridge condition -when the
transform er is strapped for 50 ohms,
change resistor values of the follow-
ing:
Rl -22 K ohms R3 -22 ohms
R2-22 ohm s R4-3.9K ohms
R5 -18K ohms
S-1
I NP UT TRANSFER
S
WI TCH
"'ICROPHONE
~
BALA NCEOl.o i'b--------
BRIOGE I
..-----0 I UNBALANCED
~....+'.+-',-----!---, I BRIOGE
V-18
LI NE
I NPUT
Fill .
120K
. R2 R3
100 100
I
I
High impedance mi crop hon e input
High impedance microphon es are not recom-
mended for u se m this equipment b eca use , in
genera l, the quality is not satisfactory for pro-
fessio
nal work. If it becomes necessary to con-
nect a hi gh impedance microphon e, the input
circuit must be re-wired as shown below:
Step 1: Remove th e input transformer Tl .
St ep 2: Remove the l00K ohm resistor Rl
from th e switch S1.
Step 3: Between pin 3 and pin 1 on the input
transformer socket, connect a resis-
2-4
tance the value of which is between
2.2
megs and 4.7megs.
Step 4: Using a jumper connect pin 3 to pin
8 on the transformer socket.
Step 5: Wire th e mi crop hon e mput con nector
for co nn ection to pins 1 and 2 (shield
to
pin 1), and lea ve pin 3 open.
Bridging a Balanced Studio line
Connect a balanced line to pins 2 and 3 of
the input co nn ec tor , Jl. P in 1 is grou nd. Pl ace
the
input transfer switch, ( S401) in the
BALANCED BRIDGE position. Input levels of
minu s 10 to plus 20 v-u ca n be accommodated.
The load placed on th e line is approximately
200K
ohms.
Br i dgi ng an Unbalanced Source
Connect an unbalanced line, rad io t urn er ,
etc ., to pins 1 and 3 of th e input co nn ec tor.
Pin 1 is the gro und side. Pla ce th e inpu t trans -
fer sw it ch S1 , in the UNBALANCED BRIDGE
position.
This connection provides a 100K ohm
bridgin g input fo: any rms program voltage
greater than .25 vo lt.
Gain Changes in Balanced Br i dge or
Unbalanced Bridge
An in cr ease of 10 db in balan ced and un -
balanced bridge can be achieved by changing
two resistors. Ch ange Rl to 33K ohms and R5
to 12K ohms. The resulting input impedances
will be 66 K ohms in th e balanc ed bridge posi -
tion
and 30K ohms in the unbalan ced bridge
position.
An mcreas e of 14 db unbalan ced bridge gain
wit h out changing balan ce d bridge g ain can
be obtained by shorting out resistor R5 and
changing R4 to 1 00 K ohms. R es ultin g input
imp edan ce will be 50K ohms.
For a 10 db mcr ease in balan ce d brid ge gain
without c hanging unbalanc ed bridg e ga in ,
c
hang e res istor Rl to 33K ohms , R5 to 27K
ohms and R4 to 5.6K ohms. Resultin g input
imp e dances will be 66K ohms for balanc ed
bridge and 33 K ohms for unbalanc ed bridge.

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SUMMARY
For Gain
Component New Value
New Input Imp edance
Increase BAL BRIDGE
UN BAL BRIDGE
10 db BAL BRIDGE
Rl 33K o hms 66K ohms
30K ohms
and UNBAL BRIDGE R5 12K
ohms
14 db UNBAL BRIDGE R5 zero (
short out ) 200K ohms
50K ohms
R4 100K
ohms
10 db BAL BRIDGE
Rl 33K ohms 66K ohms
33K ohms
R5 27K ohms
R4
5.6K ohms
PHONES
High impedance head phones must be used.
To
monitor the incoming line or reproduce
output. plug the hi gh impedance phones into
phone jack J6 PHONES on the amplifier face
panel or ]4 MONITOR on the back of the
amplifier chassis. The monitor jack J4 is a
high impedance unbalanced output isolat ed
from the main line . To preserve low frequency
response, feed into an input impedance SOK
or higher. To preserve11igh frequency response
the cable shou ld have not over 500 uuf of
capacita nc e.
RE MOTE CONTROL
The operation of the t ape transport m ec han-
ism can be remotely contro ll ed by a Remote
Control Unit. The catalog No. 5763-00 or
5763-02 unit is supp lied in a wooden case,
completely
wired and r eady to plug into the
remote control
connecto r, J502S, on the tape
transport circuits assembly. The catalog No.
5763-01
and 5763-03 units are mounted on a
flat
plate for installation in studio consoles,
and are not wir ed. For Model 351-2, use 5763-
02
in the wooden case or 5763-03 mounted on
the flat plat e. To install , wire as shown in the
figure (Sc hemati c Diagram, Remot e Control
Unit ) located in SECTION 5, and plug into
J502S.
NOTE
Whenev er th e r emote control unit is
not connected, the dummy phtg
P502P, supplied · with the equipment,
must be plugged into ]502S .
60 CYCLE AMPLIF I ER
The Ampex Model 375 Precision 60 Cycle
2-5
Amplifier
can be plugged directly into tJ1 e
equipment at J503S. No other connect ions arc
necessary. The Model 375 is used where power
sources are errat ic and there is n ee d for a pre-
cision
60 cycle time base for diivin g th e cap-
stan.
CAUTION
If this unit is used with the Recorder/
Reproducer, the control circuit fuse
F402 must be increased to 5 amperes.
NOTE
Do not remove the dummy plug
P503P unl ess th e 60 cycles amplifier
is con necte d.
OVERALL PERFORMANCE CHECK
(Read SECTION 3, OPERATION before mak-
ing these ch ecks.)
Make the following e quipment performanc e
checks
at the tjme of installation an d when
necessary thereafter:
REPRODUCE ( Playback) LEVEL
REPRODUCE (
Playback ) RESPONSE
REPRODUCE (Playback)
NOISE
MEASUREMENT
RECORD CALIBRATION
FREQUENCY RESPONSE
RECORD
NO I SE MEASUREMENT
NOTE
It should be noted that this machine
has been adjusted at the fact01y to

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produce frequency response within
specifications when recording on an
average tape. In the l ast few y ea rs th e
high frequency output from t ape has
improv ed tremendously. In order to
k ee p pace ·w ith thes e im .pro ve ment s,
in th e summer of 1959 Amp ex sel-
l
ected a 11ew "average" tap e to adjust
bias and r ec ord equa lization. Ma-
chines adju sted /: o th e n ew average
tap e may he identified by th e cata log
n11mber
of the el ec tronics , No. 30960
represe
nting the r ev ised 1nach 'i n e. Th e
30960 electronics also
ar e a djust ed
for a 3¾ inch es per seco nd (i ps )
pl
ayback r es ponse cur ve incorporat-
ing a 120 m.icroseconcl turnover.
tion m eter wi ll be more accurate th an tho se
fro m a null t ype instrument at l ow er distortion
levels.
Distort i on readings are som ewhat de-
pe
nd ent on ta pe. A re a ding of 1% is normal
at op e rating level while a r ea ding of 3% is
n ormal at 6 db above operating level. Seco nd
harmoni c dist or t ion is ne gligibl e; m eas ur ed
dist
or tion is pr edominately third order.
FLUT T ER AND WOW
Compl ete inst ruc tions for m ak in g the above
checks
are given in SEC TIO N 7 ALIGNMENT
AN D PERF OR MANCE CH EC KS.
F
lu tter and wow arc prod uced by periodic
ineg ul ar ities in ta pe speed an d app ea r as cyclic
fre qu ency deviations in recor di ng or reproduc-
tion. They
ca n be measured by means of any
s ta n dard fl. utter b ri dge. Variations in ampUtudc
as in di cated on level me asureme nt s do not
con st itute flutter and are e ntire ly due to tap e
coating variations. R
ea dings will be near or
below .1 5% rms at 15 inch, .2% rms at 7½
in ch, and .25% rms at 3¾ inch speed. Th e
Amp
ex Professional Products Division primary
stan d ard of m eas ureme nts is based on th e u se
of a fl ut ter meter calibrated to in di cate th e
d
eviat i on from m ea n carr i er fr equency of any
rat e between .5 and 300 cps expressed in pe r-
cent rms. Flut t er and wow ch ecks s ho u ld be
made
at th e peak recor d level or hig her.
DISTORTION
O
ve rall di stortion can be m easure d by con-
n
ec tin g any sta nd ard di sto rtion m easure ment
a
pp aratus ac ross th e ou t put. The read i ngs from
a wave analyzer or se l ect ive frequency di stor-
Cu.tulog
Cn/,le
No111l> er
A-c 24 13- 00
Pow er
ln tercono cc tin t:,
Reproduce
H
ead
Re cor d
Head
Erase
Head
Pow er
3768-0 1
Extension
Pow er
30926-0 1
l
nt e rconn ec::ling
Bias
l 4943-02
lnl er con nc cting
30!!26-02
IN TERCONNECTING
S INGLE TRACK
From
Qty , Recl'p tacl e C
ha ssis
(I J
J8 POWEn
El ectro ni c
Assembly
( l ) J7 TAPE El
ec troni c
TRANSPO
RT
Assembly
( l )
,1 3 PLAYBACK E
le ctro ni c
llEAD
A sse mbly
( l )
J2 RECORD EleclJ'onic
HEAD As~embly
( 1) J10 ERASE Electronic
HEAD Assembly
PORTABLE
SI NGLE TRA CK
( I ) J7 TAPE
TRANSPORT El
ectro ni c
A
ssemb ly
DU AL TRACK E(?U IPME NT
(UnmountedI
( l ) J7 TAPE
Electronic
TRANSPORT Assembly
I
and 2
From
{ I ) J9 RI
AS Master
COUPLI NG El ectro ni c
Assembly
DU AL TR A C!< E c;'IUIPM E NT
(Po r tab leI
.17 TAPE
El ectro n ic
TR ANSPORT Assembly
J ancl 2
To
Receptacl e
Chassis
A ~c so urc e
CABLE TO
Ca ptive at
EL ECTRONICS Tape Tr anspor t
C
aptive at Tape Transport
Ca pti ve al Tnpe Tr an spo rt
Ca ptive at Tape Transport
End of C;i ptiv e Tape Transport
power int er co nn ect in g ca ble.
End of Ca ptiv e Tape Transport
power inter connec tin g cable.
To
J9 BIAS Sl
ave Elec tr on ic
COU
PLIN G Assembly
End of Cap ti ve Tape Transport
po w er interco11n ec tin g cab l e.
NO TE : Cnhl es rnarkl'd w(th n rc:d b"nu, interconnect in up p er el ec tronics for
1h e Model 35 1-2 only,
2-6

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INTERCON N ECTING
~ -- -----~- ,
,,.-_------ ---L- -------~~
1 RED OR TRACK 1 I I
r~p,roduce
i;;_od-
2s
__ _ i_6 __ 0_
2
__ _ l ~--() -2 ___ _____._ Iii
l~ record heads erose heads
I
coble to e lectronics
I
notes 2 and 4 J
,--- - - - - UPPER TRACK
1 .-------~- - ---- ----+---------4------ - --
1 note 1.--- MASTER ELECT RONIC ASSEMBLY
power
G)
"'
u
<
"'
--
"'
0
0
w
"'
"'
u
<
"'
--
"'
0
0
w
"'
.: :''":•S'@c:;; ,~r or· 0-i:~ .. c';r· o~~::@·o 0
I b
k.
colibrolion O J2 Jl
I I S4 0 boos C13 [Q]
0
line output I P oy oc 0 . record li ne
JS lope transport ,;;:.. I head J3 b, ~s head inpu t
r\ Q J7 ~ od1ust
~ monitor amplifier I '-- ---- -------1~
fuse J4 I
I
i LOWER TRACK
SLAVE !
ELECT RONIC ASSEMBLY
I
I
I
I
I
I
I
I
I
11
I I
11
11
11
I I
11
11
I I
II
I I
I I
1 1
I I
I I
I I
1 1
I I
I I
I I
:--note 3 : :
I I I
: r _____ ___ l l
-f--0 --- ~1::1~:~s:@~ r:':";~~:r61 101 0,i::·g;""l6J~i~~@ eo 0 l
I I S-4 ~ ~ bias C13 I OI I
0 . lo bock calibration O J2 . Jl I
tape transport liner;;;;\outpul P Y 0 b" record l ine
0 Q J7 ~ heod J3
0~~;st L
head input j
~ monitor amp lifier 1 ---- · - -
fuse
J4
NOTES,
1. A
3768-01 POWE R EXTENSION CABLE IS USED WIT H SI NGLE TR A CK PO RT ABLE EQUIPM E NT .
2.
30926-01 INTERCONNECTING CABLE IS USED WITH DUA L TRACK STEREPHONIC EQU IPMENT.
3. A
149.(3.02 BIAS INTERCONNECTING CABLE IS USED WITH POR T ABLE DUAL TRACK
STEREOPHONIC EQUIPMENT.
, . A 30812 - 02 POW ER INTERCON NE CTING CA B LE IS USED WITH PORTABLE DUAL TRACK
STEREOPH
ON IC EQUIPMENT.
2-7

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Model 351 Console
2-8