Electro-Voice DB23 Specifications And Instructions

Slecho Voice
ELECTRO-VOICE, INC.
BUCHANAN, MICHIGAN
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Schematic Diagram
6-3-Le
Specifications and
Instructions
RME Model DB23
Preselector
The DB23 preselector is a low-noise, radio-frequency amplifier which can be
used to substantially improve receiver performance on the following amateur
radio bands:
3.5 mc to 4.0 mc
7.0 me to 7.3 mc
14.0 me to 14.5 me
21.0 me to 21,5 mc
26.0 mc to 30.0 mc
The DB23 consists of one tuned input circuit, which matches input impedance
of 75 ohms unbalanced or 300 ohms balanced, followed by two stages of low-
noise, neutralized, broadband push-pull 6J6 amplifiers. Finally, a push-pull 6J6
impedance matching stage delivers the amplified signal to the receiver with out-
put impedance of 150 ohms unbalanced or 300 ohms balanced. Input and out-
put impedance values actually encountered can differ within reasonable limits
without seriously affecting performance.
The voltage gain which can be expected from the DB23 varies somewhat with
the band in use and the output impedance selected (balanced output gives 6 db
more gain). Minimum gain, using a balanced output connection, will be about
26 db, while maximum gain, using the same output circuit, will be around
35 db. The tuned circuit in the DB23 adds selectivity to the receiving system
The amount of image rejection due to the-DB23 varies with the frequency, and
can be as high as 30 db on the lower frequencies.
Because the DB23 is a low-noise device, an improvement in signal plus noise-to-
noise ratio (or usable gain) is experienced. This feature is quite pronounced
with the less sensitive receivers, but even the better receivers will benefit. An
improvement of 7.5 db in signal plus noise-to-noise ratio is not unusual,
SPECIFICATIONS
Tubes: V1 6J6 R.F. amplifier
V2 6J6 R.F. amplifier
V3 6J6 R.F. impedance matching amplifier
Power Supply: Self contained; uses transformer and selenium rectifier
Input Impedance: 75 ohms unbalanced
300 ohms balanced
t Impedance: 150 ohms unbalanced
300 ohms balanced
Gain: 30 db (average)
Frequency Range: 3.5 to 4.0 mc; 7 to 7.3 mc; 14 to 14.5 me;
21 to 21.5 mc; 26 to 30 me.
Size: 7% in. wide x 6 in. deep x 5 in. high
Weight: 64 Ib, shipping