SHURE BROTHERS
INCORPORATED
Micro-honnc and Acou-tic Devices
225 WEST HURON STREET :: CHICAGO 10, ILLINOIS PHONE DElaware 7-4550 :: CABLE: SHUREMICRO
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DATE: M A Y 1949 |
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SUBJECT: Model 901D Verfical Drive |
'lTurnover1'Crvs+al Ph o no - |
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graph Pickup |
MODEL 981D
Ver+iea! Drive 'Turnover" Crystail Phonograph Pickgap
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General: |
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Model |
901D |
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"Turnover" |
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Phonograph |
Pickup is |
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designed |
t o |
reproduce standard |
records |
and |
the |
various |
types |
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o f fine-groove |
long playing |
records. |
M o d e l |
901D |
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uses |
a |
turn- |
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over mecl?ar~isman2 the new Shure two-sided "Vertical Drive" |
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crystal cartridge. |
The crystal element |
is |
a |
bimorph, |
Rochelle |
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Salt unit. |
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This dual-purpose cartridge utilizes the |
"Vertical |
Drive" |
con- |
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struction |
which |
results i n a needle-point compliance |
in the |
order |
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o f 1.0 |
x |
10-6 centimeters per dyne. |
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By |
combination |
o f |
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this |
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highly compliant cartridge and the Shure die-cast aluminum |
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pickup arm, an extremely low needle force for proper record |
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tracking |
has |
resulted. |
The |
dual |
purpose |
cartridge |
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has |
a |
Shure |
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Model A 5 2 A osmium |
tipped |
needle |
(.003" |
needle |
t i p |
radius) |
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f o r playing standard |
records |
a t |
78 |
r.p.m. |
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and |
a |
Shure Model |
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A 6 5 M G |
sapphire |
tipped needle |
(.001" |
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t i p radius) |
for |
playing |
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Columbia, |
R.C.A. |
and similar |
fine-groove |
records a t 33-55 r.p.m. |
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o r 45 r.p.m. |
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These needles are separately replaceable. |
The |
Pick- |
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u p performs |
equally |
well on |
the 7". |
lo", |
o r |
12" |
size |
records. |
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Model 901D will give an excellent frequency response with |
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high output and extremely low tracking |
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force. |
The |
design |
o f |
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the pickup provides record reproduction with low surface noise, |
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low needle talk, end low needle hiss. |
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LOW record |
wear is assured by +he |
curved |
tone-arm |
(which |
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maintains |
the |
horizontal projection |
o f |
the |
needle |
closely |
tan- |
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gent t o the |
groove et all times), by |
high |
needle |
point |
compli- |
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ance, |
and |
low needle |
pressure o f |
6 grsx: |
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( ? $ ounce). |
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A n |
adiustment |
screw is |
provided |
for |
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the |
swivel |
t o |
protect |
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t h e needie |
against damdge'due t o |
accidental |
touching 'of the |
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' turntable when recoid is removed. |
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Model |
901D |
"Turnover" |
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Pickup |
is |
provided |
with |
a |
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14" |
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shielded |
lead. |
A n arm resf |
is |
included |
for |
mounting |
on |
the |
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motor-board. - |
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Applica3ierns: Model 901D is ideally suited for the ex- |
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perimenter and for use in high quality home |
~ h o n o ~ r a p h spor,- |
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table equipment, and record demonstrators. |
This |
pickup |
is |
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especially |
suited |
for |
replscunent o f |
older, |
heavy |
~ i c k u p s as |
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. well as pickups used |
in modern |
installations. |
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Because o f low needle talk and needle hiss, the model 901D
may be used with open-type phonograph players with a mini-
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mum o f arrnaying side tone.
The output voltdge o f |
the pickup (see ~ ~ e c i f i c a f i o n sis) suf- |
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ficient |
t o produce |
full |
output from audio stages o f modern |
radio |
receivers and |
from |
moderate gain amplifiers. |
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- - |
- .. - |
- - |
A |
c. Tighten |
the |
locking |
nuts |
securely. |
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The arm rest should be mounted in any convenient place on
the |
motor-board |
in such a manner that it does not interfere |
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with |
the playing o f |
a |
12" record. |
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If necessary, the length of the leads can be increased con- |
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siderebly without excessive output loss. Low-capacity shielded |
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cable is suitable for this purpose. |
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Nothing should interfere with the free motion o f the Pickup. |
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Leads (or |
cable) |
should be allowed to extend several inchtr |
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before making connections, so that the pickup may rotate freely |
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obout its vertical |
axis. |
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Suificient |
cabinet |
ventilation |
should |
be provided |
t o |
keep |
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the ambient temperature about the pickup at the lowest pos- |
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sible value. |
For |
best results the ambienf temperature should |
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not be allowed t o |
exceed 100' Fahrenheit, although no damage |
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will |
result to the Pickup below 125' Fahrenheit. |
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Conaeefisns: |
~ o d e l901D |
pickup |
utilizes |
the |
pin-jack |
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method o f connecting the leads |
t o the |
cartridge. |
One side |
o f |
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the |
crystal |
unit is |
connected t o |
ground |
through the |
shield. |
In |
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this instance, the pickup may be connected directly into an |
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amplifier of the type using a single grid input circuit. The cen- |
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ter conductor should be connected to the grid or |
"hot" |
lead: |
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the |
shield should |
be |
connected |
t o the ground or |
chassis. |
Fig- |
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ure A shows the circuit. |
The chassis should be securely grounded |
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t o eliminete shock |
hazard t o the |
user. |
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Bns+rril!a4ioas: The Pickup should be mounted on the motorboard so that the oifset needle furnished with the pickup has an arc o f travel approximately y4" beyond the center o f the turntdble spindle. (See Fig. C). The motorboard should be heavy and well isolated from vibrations o f the motor and the loudspeaker.
A f t e r the |
pickup is |
securely |
m o u n t ~ dthe following |
proce- |
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dure rnay b e followed |
t o install |
and adjust the needle |
protec- |
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tion |
screw. |
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Assemble one hex nut on the l/z" long |
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a. |
L i f t the |
tone arm. |
needle protective screw and insert screw into the hole provided in the swivel assembly bracket with the head of
the screw toward the inside |
o i the |
arm. |
Assemble other |
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hex nut t o the |
portion o f the |
screw |
extendins t h r o ~ l g hthe |
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bracket. |
The screw |
and two |
hex nuts are |
provided j n the |
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accessory box. |
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b. W i t h |
a |
screwdriver |
adiust |
the screw until the needle |
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point, upon lowering the tone-arm, Is maintained approxi- |
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mately |
1 /32" |
above |
the turntable surface. |
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Copyright |
1949, Shure Brothers, Inc. |
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2-7wr- |
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A 6 i A
3 MII Radius Needle
PPNO56467 Pdn
On ~ o i dTern~no l
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Arnptil,er |
IMil ~ c usd Needle |
PNo 56467 Pin J O C ~ |
Chossls |
(Red) |
On Sdver Termmot. |
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Pig. A. F o r A m p l i f i e r s |
Using a S i n g l e G r i d lnpuf . |
Q)per~*ig311: To play standard (78 r.p.m.) records, set the knob at the front of the pickup so that the letters STD are a t the top. To play microgroove and R.C.A. slow speed records, turn knob in the direction of the arrow until the letters MG are
Printed in U.S.A.
a t the |
top. The knob may be used as a convenienf handle t o |
set the |
pickup on the record. |
The needles may b e rzmoved by loosening the knurled nut (which holds thc needle) l/z turn. A new needle should be inserted in the hole provided and the knurled nut tightened securelv ~tsinathe thumb and fore-finner. Care should be taken ,t t o deform the contour o f the needle when the knurled nut
tightened.
Model 901D uses the Shure "Muted Stylus" |
needles which |
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may be procured in any record shop |
throughout the country or |
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a t any |
Shure distributor. |
The |
pickup |
is supplied with the A62A |
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(.003" |
t i p radius) precious metal t i p |
needle which is o f natural |
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stainless steel color and the A h S M G |
(.001" |
t i p radius) sapphire |
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t i p needle which is dyed |
red. |
Instead o f A62A, |
an A 6 1 A sap- |
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phire t i p need!* may be used for longer life. |
In portable phono- |
graphs, when pickup is not in use nsedles can b e protected against accidental damage by rotating the turnover mechanism 90".
Record Wear: |
LOWneedle pressure and low needle point |
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impedance |
(resistance t o side-to-side |
motion o f the |
needle) |
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are |
achieved through |
an unique system o f mounfing and coupl- |
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ing |
the |
crystal unit. |
These features permit the ncedle |
t o ride |
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through |
the |
record-groove with a minimum o f thrust and wear |
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on the |
side |
wal!s. Record wear is still |
further reduced |
by the |
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off-set {earl |
o f the pickup, which keeps the normal axis |
o f rota- |
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tion |
o f |
the |
needle |
closely tangential |
t o the record |
grooves |
throuqhout the plavinq time o f the record. This results in low
trackinn error, dnd'inmaximum fidelitv o f |
reoroduction a t |
all |
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frequencies. The pickup should |
be carefully |
located as specified |
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under "Installation" |
t o derive |
full benefit |
from this feature. |
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i ' + ~ q ~ e Response:f ~ |
The frequency |
response curves |
o f |
the model 901D obtained on Columbia micro-groove test record No. 281 and Audiotone test record No. I are shown in
figure B. |
This |
type o f |
response is very satisfactory |
for high |
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quality reproduction o f records without i h e use o f |
compensating |
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circuit:. |
Ton- |
con:ro!s |
provided in the |
maiority |
o f |
amplifiers |
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and radio |
receivers |
may be |
employed |
t o alter this |
frequency |
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response |
t o |
suit |
the |
individual |
listener. |
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AFSPOHSE FREQUEhLY CHARACTERISTIC |
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nv |
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$+I0 |
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z |
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0 |
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a |
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,I |
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W |
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2 |
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5-10 |
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IlJ |
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a |
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5 0 |
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100 |
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COO0 |
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l0,OOO |
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FREQUENCY-CYCLES PER SECOND |
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-Audlorone |
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Test Record No 1, 0 0 2 7 Needle 1lp Rodtur. |
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I IVoIxs Output A1 1000C P S |
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------CclurnSa |
Test Rccrd No281.001 Needle Tap Rod~u, |
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94 Volts 0ufi)utAt 1000 C l?S |
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Fr'g. C. Physiec! Dimensions o f Mode! 901D.
Vo!.kalle Sensi)i\ri*y: |
The output voltage depends upon |
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the individual |
recording. |
etc. |
Model 9 0 i D has |
an outpuf o f |
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approximately |
.94 |
volt at |
1000 |
cycles on Columbia test record |
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No. 281 and |
1.1 |
volts on |
Audiotone test record. |
Peak voltage |
output on commercial records may reach 10 volts.
!mfertid Ipnpedance: Equivalent t o 650 mmf condenser.
Recommended Load impedcifice: I/,n-egohm or more.
depending upon the response curve desired.
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MODEL 901D |
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1- |
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FINISH |
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GRAY H A M M E R ENAMEL |
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C O D E W O R D |
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RtJZEL |
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LEAD |
LENGTH |
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14" |
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ARM REST |
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INCLUDED |
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NET W E I G H T |
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4 |
02. |
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NEEDLES |
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REPLACEABLE, L O N G - |
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LIFE, INCLUDED |
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SHIPPING W E I G H T |
I 2 |
02. |
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F i g . R. Typical Response Gharacterisfics of 904D. |
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Guaranfee: |
Every |
Shure |
Pickup i s |
guaranteed |
t o be |
free |
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The low-frequertcy response |
below approximately 500 cycles |
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from electrical |
and mechanical defects |
for one year |
from |
date |
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of shipment from the factory, |
provided all instructions are |
com- |
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depends |
upon the |
termination |
resistance. The user can |
thus |
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plied with fully. |
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adjust the low-frequency response over wide limits by p:oper |
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choice o f |
resistance |
o f the input potentiometer or grid resistor. |
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License Nofice: |
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A value |
o f I to 2 |
niegohms will be satisfactory in most cases. |
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Shure |
Crystal Record Reproducers |
are |
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The high frequency response is not affected by the value o f the |
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licensed under patents o f the Brush Development Company. |
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termindtion resistance. |
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Shure patents |
allowed |
and pending. |
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2 7 ~ 4 2( 5 - 4 9 )