Western electric 124 a schematic

Page 2

Wes/em Electric Company
No. l 24-A AMPLIFIER

The 124A Amplifier is a two-stage fixed-gain amplifier intended for loud
speaker operation.

Typical Electrical Characteristics

Gain-Approximately 63 db, high gain input connection
Approximately 50 db, bridging input connection

Frequency Characteristic-Uniform within : 1 db over the range 30 to
15,000 cycles

Operates from-600 ohms nominal impedance

Operates into-600, 150, 30, 16, 7.5 or 175 ohms nominal impedance

Output Power-12 watts as shipped, 20 watts available

Output Noise-Unweighted, 37 db below .001 watt

Power Supply-105-125 volts, 50-60 cycles. 1.25 amperes, 125 watts
maximum

Apparatus Description

Dimensions-19552 inches wide, 7 inches deep and 7 inches high (Panel
Space)
Weight-Approximately 20 pounds
Finish-Chassis-Aluminum lacquer
Mat-Black Japan, coded 124A-3-Aluminum Gray, coded
124A-1 5

ASSEMBLY
Load Impedance

The amplifier is shipped with the output transformer connected for a
nominal load impedance of 7.5 ohms. If the load impedance is not within the
range of 3 to 10 ohms, the output transformer should be reconnected for the
proper impedance as indicated in the table on the Schematic drawing. Figure 1,

Output Power

The amplifier is furnished connected for an output power of 12 watts. In
the interests of minimum operating temperature and maximum vacuum tube
life, it is recommended that the amplifier be operated as furnished unless more
power is required. If an output power of 20 watts is desired. it is only necessary
to replace the two orange colored wires connected to the rectifier tube socket
(marked 5U4G-274B) with the two unconnected red wires having taped ends.
The orange wires removed should be similarly taped Operation of non»\Western

Instruction Bulletin No. 992P

*114