Western electric 121 a schematic

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Maren! Electric Company

No. | 2 | -A LINE AMPLIFIER

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\\_J/// Figure 11 - IZIA line Amplifier.

Use . - An adaptable 78 db fixed gain amplifier unit for
use as an intermediate or microphonetorline level main
amplifier in FM and AM speech input and sound dlSUlbLlr
tion systems.

Descripfion ¥ It is a three stage 78 db fixed gain amplir
fier having low distortion and high signalrto-noise ratio
Input impedances of 50, 250, or 600 ohms can be selecced
by arranging the strapping to the input transformer. The
output impedance is 600 ohms. Each cathode circuit is
arranged for checking the tubes through the use of the
KS-10003 type or equivalent meter. The total d-c power
required is 0.03 ampers at 275 volts. The filaments require
2 amperes at 6.3 volts.

The construction is compact and rugged resulting in 11
small chassis size for this type of amplifier.

Features

Three-stage fixed gain amplifier.
Intermediate or microphone-to-line amplifier.
Ready checking of tubes.

Ease and variety of mounting.

Electrical and mechanical isolation
Stabilized feedback.

Specifications

Frequency Response: Uniform within :1 db over the
range 50 to 15,000 cycles.

Output Noise: (Weighting follows normal ear sensitivity
curve).

Gain 73 db 70 db 45 db
Noise Level:
L'nweighted -42 dbm -50 dbm 775 dbm
\Xeighred -52 dbm 760 dbm -SS dbm
A; + 18 dbm out/71:1 let'el signal-m-noise ratio:
Unweighted 60 db 68 db 93 db
Weighted 70 db 78 db 103 db

Source Impedance: 30, 250 or 600 ohms matching. For
bridging add proper input pad.

Load Impedance: 600 ohms.

Maximum Gain: 78 db; 70 db by internal connection
change; 45 db by restrapping to eliminate the first stage.

Output Power: Single frequency output power for less
than 1 per cent total harmonics: +28 dbm (600 milli-
watts) for fundamental frequency of 400 cycles: + 25 dbm
(300 milliwatts) for fundamental frequency of 50 cycles.

Power Required: Filaments, 6.3 volts, 2 amperes; plates,
275 volts, d-C, 30 ma.

Power normally obtained from Western Electric 18 or
20 type Rectifiers.

VACUUM TUBES

Commercial

Quantity Required 17:11:17: Elerm'c Receiver Types

1 347A or 617 (or 1620)
1 348A at 6J7 (or 1620)
1 349A or 61:6 (or 6V6)
3

Mounting: This basic amplifier unit is designed for mount-
ing in desks or other structures; also adaptable for relay
rack or bay cabinet mounting through the use of 177 or
190 type mounting plates and 296 type panels. Isolation,
borh electrically and mechanically, is accomplished by using
rubber supports which are furnished with the amplifier.

Dimensions: 10-3/16" Wide, 10-15/32" deep and 6-3/16"
high.

Weight: 10 pounds.
Finish: Light gray.

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