Shure 812 User Guide

222

HARTREY AVE . EVANSTON,

ILL

CABLE SHUREMICRO

MODEL

812

EVANSTON PHONE DA.8

General:

a high quality recording unit designed for use with stainless steel wire, plated wire, or other presently available wire recording mediums.

The radio experimenter, technician, or amateur can use the

Model 812 with its associated circuits to construct home recording or professional equipment. Model 812 Head is an exact replacement for Shure improvement over Shure

The Model 812 Magnetic Wire Recording Head combines in

single unit the functions of recording, reproducing, and signal

erasure.

Applications:

types of wire recording and playback applications sional, semi-professional, and home recording types. This data sheet contains information for the correct use of Model 812 head in such equipment, but not for the design of the equipment itself.

The recording head is of rugged construction and immune to all effects of moisture, temperature, and mechanical vibration. The wire groove in the recording head has been carefully contoured and

polished to give uniform response, high erase efficiency, and

long operating life.

The outer metal case affords excellent hum shielding which

minimizes the ducing components. Reduction of hum-pickup to a low value also gives greater freedom in low frequency compensation.

Model 812 Magnetic Wire Recording Head is

WR-I0 heads.

The Model 812 is suitable for use in all

problem of the mechanical

9000

CHICAGO PHONE SH

WR-12 heads, and

placement of hum-pro-

3.1600

high quality

constitutes an

the profes-

MODEL

CODE WORD

SPECIFICATIONS

8 12

RUWlR

Installation:

adapter base and may be mounted to the mechanism by using the 4-40 threaded holes in the base of the unit. (See diagram).

The recording head may be mounted in any position the wire enters and leaves the groove at the angles recommended in figure D.

Connections:

and playback coil, the erase coil, the laminations and the shield are shown in figure A. The base pin connections are also shown. Pin No. 4 is the "hot" side of the record and playback coil. Pin

is the "hot" side of the erase coil. Pin

No. return for the record and playback and erase coil. Pin No. I is

the lamination and shield ground.

COMMON

RECORD.

ERASE I PLAYBACK

~EGATWE

BIAS

ERASE

Operation:

given for the Model 812 in the table on next page.

The solid line curve in the response frequency characteristic of figure ing data. For this curve

is obtained using the data given in the typical operat-

The Model 812 has a standard 4-prong

The internal connections of the record

No. 2 is the common

FIGURE A.

$$2

BIAS.

FOR

D.C.

VOLlA4

CIRCUIT DIAGRAM.

$$I

ERASE

POSITIVE

FOR

D.C.

ERASE

[VOLTAGE]

Typical operating currents and data are

LAMINATION

millivolt.

RECORD.

BIAS

providing

1.1

NET WEIGHT

SHIPPING WEIGHT

DIMENSIONS

The response of the Model 812 Wire Recording Head may be equalized in the region an interstage compensating network as shown in figure work is designed to couple a high gain or triode and operates in both the record and playback functions. When recording, the input terminals are connected to the microphone, and the output terminals to the wire recording head. In playing back, the wire recording head is connected to the input

terminals and the output terminals are connected to the speaker. The detailed arrangement of components, other than the compensation network will depend upon the design chosen by the user. The broken line response shown in figure that is achieved with the interstage cornpensating network shown in figure quency playback emphasis is afforded high frequency emphasis may, of course, be added in the playback network depending upon individual distortion and noise level requirements. The compensating network introduces a loss of 20 db. Therefore, the amplifier must have quired in using an uncorrected

operating data table on the following page and may be employed where direct current erase and bias operation are applicable. The terminal connections for D.C. bias in figure A. The response frequency characteristics are essentially the same as shown in figure

high frequency recording emphasis and a low fre-

D.C. Erase and D.C. bias current data is shown in the typical

Guarantee:

be free from electrical and one year from date of shipment from the factory, provided all instructions are complied with fully. In case of damage, return the wire recording head to the factory for repairs. Our guarantee is voided

the wire recording head case is opened.

100 c.p.s. to 8000 c.p.s. by means of

Each wire recording head is guaranteed to

mech~anical defects for a period of

OUNCES

I OUNCES

SEE

FIG. D.

pentode to another pentode

indicates the response

by this network. Additional

a~dditional gain above that re-

reco~rding head.

,and erase operation are shown

Shure Patents issued and pending.

(O\

Printed

This net-

U.S.A.

FIGURE D. DIMENSIONAL DIAGRAM.

1-1/2

TYPICAL OPERATING DATA

Bias and Erase Freq.

Recording

Current (ma.)

25 kc I 33

----

.43

----

Bias Current

(ma.) (Rec.

Coil)

Erase Current (ma.)

(*I

Erase (Volts)

Erase (Watts)

Impedance

Erase Coil

(*)

Erase Current chosen for 40 db erasure of 400 c.p.s. signal, re-

corded with typical Recording and Bias Currents.

IMPEDANCE Recording

.001", 800 ohms at I kc.

Gap

INTERSTAGE COMPENSATING NETWORK

----

.OO

----

650

ohms

Playback coil,

FIGURE

3 .O

1.30

770

ohms

3.0

1.65

890

ohms

D.C.

.43

2.25 D.C.

60 D.C.

0.75

.05

ohms

FIGURE

RESPONSE FREQUENCY CHARACTERISTIC.

FREQUENCY-CYCLES

Recording Medium:

Wire, National Standard Company, Specification Wire Speed 2 Feet Per Second.

.004"

PER

SECOND

Diameter Stainless Steel

AMPLIFIER

W555.

PLAYBACK

REC: RECORD