This low-power amplifier on a modular sub-card is designed to drive a
10...15 Ω speaker. Power output is about 2...3 W. As can be concluded
from this specification, the amplifier is not intended for high-quality monitoring. It will be ideally suited, however, for pre-fader listening and similar
applications. The amplifier’s input is balanced and floating, with adjustable
gain.
Technical Specifications
Input impedance > 10 kΩ, balanced and floating (with transformer) Nominal power output 2 W into 15 Ω Power output 25 mW...2.5 W into 15 Ω, with 0 dBu input
Distortion < 0.5% at 2 W < 0.15% at 500 mW
S/N 99 dB, ref. to 2 W at max. gain
Frequency response –0.5 dB at 15 kHz High pass filter 150 Hz, 12 dB/oct.
Supply: –24 V (40 mA idling, max. 220 mA fully driven)
Two different microphone pre-amplifiers are available, for dynamic or
condenser microphones, and for electret microphones. Both offer high gain
and low noise, as is required for microphone pre-amplification.
1.914.506 features a balanced and floating input. It is designed for dynamic
or condenser microphones with a source impedance of 200 Ω or less. An
RF filter is incorporated at the input transformer’s primary. Furthermore,
the input is equipped with the resistors required for phantom powering of
condenser microphones.
1.914.507 is designed for unbalanced electret microphones requiring a
12 V supply.
A wide range of input levels can be accommodated (see level diagram).
By using the same solid-state switching circuit as can be found in the line
and high-level amplifiers, remote muting or activation of a fixed amount of
attenuation are possible as well.
The amplifier’s two outputs are unbalanced, with impedances of 3.3 kΩ or
33 Ω, respectively.
Date printed: 11.12.2006
Professional Audio System Components
Technical Specifications
Input:Transformer-balanced and floating, with RF filter (1.914.506) Unbalanced, with RF filter and electret supply (1.914.507)
Impedance > 1 kΩ, for microphones with an impedance of 200 Ω or less.
Max. input level –2 dBu (615 mV
Common mode rejection > 60 dB, unbalanced, to ground
Output:Max. level +20 dBu (7.75 V
Nominal level 0 dBu (0.775 V
Impedance 33 Ω (pin1)
3.3 kΩ (pin2; to a 0-Ω amp.)
Minimum load 600 Ω
Max. gain 71 dB (see level diagram) Frequency response ±0.5 dB, 30 Hz...16 kHz
THD < 0.3%, 30 Hz...16 kHz at 20 dB gain Noise figure, linear < 4.5 dB, input terminated with 200 Ω
Supply: ±15 V (11 mA idling)
+48 V (1.914.506, only if phantom powering required)
Dimensions: MS-card, 34 × 85 mm
Ordering Information: • Microphone pre-amplifier for dynamic microphones 1.914.506.xx
• Microphone pre-amplifier for electret microphones 1.914.507.xx
); THD at 30 Hz: approx. 1%
rms
)
rms
)
rms
Date printed: 11.12.2006
Professional Audio System Components
VCA with Electronically Balanced Connections 1.914.515
In contrast to the VCA module 1.914.518/528, this assembly features elec-
tronically balanced input and output.
It is intended for use in balanced audio systems for a variety of applica-
tions, especially when gain is to be controlled from a remote point. It will
be useful in audio-video post-production work where suitable DC ramps
can control cross-fades, voice-overs, etc. Its high overload margin and its
exceptionally low noise and distortion performance make it the perfect
choice for high-quality audio applications.
By connecting the gain control terminals of a number of VCAs to a com-
mon potentiometer or fader, several audio channels may thus be controlled
simultaneously.
Two control inputs provide VCA gain control from two different remote points
Output:Electronically balanced
Recommended load ≥ 2 kΩ
Maximum level +24 dBu
Frequency response –0.5 dB, 30 Hz...15 kHz
Gain/attenuation range +40...–100 dB, with ext. control
Control input: pin1; gain tracking 0 V = unity gain; 1 dB/µA; jumper 1-2 20 dB/V; jumper 2-3 10 dB/V; jumper 3-4
Control input: pin10; gain tracking 10 dB/V
THD < 0.1% Equivalent input noise –93 dBu @ unity gain
Supply: ±15 V (25 mA)
Dimensions: MS-card, 34 × 85 mm
Ordering Information: VCA with electronically balanced input and output 1.914.515.xx
Date printed: 11.12.2006
Professional Audio System Components
VCA with 1 or 3 Control Ports 1.914.518/528
Within the range of modular sub-cards, two more VCAs are available.
Voltage controlled amplifiers are ideally suited for applications such as
remote level control, level limiting (in combination with the voltage processor 1.914.519) or for automatic “voice-over” circuits, when driven by
suitable ramp generators. These VCAs offer outstandingly low noise and
harmonic distortion.
For best performance, they should be operated at a level of 0 dBu.
Gain pre-selection is possible on the 1.914.518 version, allowing gain/at-
tenuation ranges either from +10 to –90 dB or from +40 to –70 dB, using
an external potentiometer.
The 1.914.528 VCA card differs in that it is equipped with three external
control inputs, providing gain control from three different locations.
External gain control +40...–90 dB (1.914.518.xx)
+40...–100 dB (1.914.528.xx)
Gain/attenuation range (pot. meter) +40...–60 dB / +10...–70 dB / +10...–90 dB (1.914.518.xx only, jumper-
Ordering Information: Voltage controlled amplifier with 1 control port 1.914.518.xx
Voltage controlled amplifier with 3 control ports 1.914.528.xx
Date printed: 11.12.2006
Professional Audio System Components
Limiter Voltage Processor 1.914.519
Together with this voltage processor, the VCAs 1.914.518/528 can perform
as signal level limiters.
The processor’s threshold can be set within a wide range of levels, so that
limiting action becomes effective at a desired level within a range of
–15 to +15 dBu. Limiting action attacks within 1 ms, whereas release can
vary from 50 ms to 5 s, depending on the program’s energy content. This
means that no audible “pumping” action – which is often associated with
such a device – will occur. After the cessation of loud passages, amplification will recover only slowly. For stereo applications, a two-channel set-up
(VCAs and voltage processor) can be linked, so that identical amounts of
gain reduction will take place simultaneously in both channels.
The input of the voltage processor has to be wired to the output of the
VCA. The processor’s output, when connected to the VCA’s control terminal, will effect the necessary gain reduction so that a limiting characteristic
is obtained. The limiting threshold is adjustable in a wide range. Remote
on/off switching of the limiter function is possible.
Date printed: 11.12.2006
Professional Audio System Components
Technical Specifications
Limiter: Input impedance ≥ 10 kΩMax. input level +20 dBu
Frequency range 30 Hz...16 kHz Output voltage 0...–13 V
Threshold level –15 dBu...+15 dBu
Attack time 1 ms
Release time 50 ms...5 s, program-depending
Compression ratio 20:1, in conjunction with a VCA
Supply: ±15 V (10 mA)
Dimensions: MS-card, 34 × 85 mm
Ordering Information: Limiter voltage processor 1.914.519.xx
DC
Date printed: 11.12.2006
Professional Audio System Components
1900 Hz Signal Generator 1.914.520
This signal generator produces a stable frequency of 1900 Hz to establish
communication on outside broadcast lines, as specified in the EBU/CCIR
recommendations.
Technical Specifications
Frequency 1900 Hz (adjustable)
Distortion < 1%
Output level –15...+6 dBu (adjustable)
Output balanced and floating Output Impedance, out 1 < 15 Ω
out 2 600 Ω
Minimum load 200 Ω
Supply: ±15 V (20 mA)
Dimensions: MS-card, 34 × 85 mm
Ordering Information: 1900 Hz signal generator 1.914.520.xx
Date printed: 11.12.2006
Professional Audio System Components
Call Decoder 20...60 Hz 1.914.521
This assembly features a call receiver for the ringing frequency on tele-
phone lines (20...60 Hz). The receiver can activate an optical and/or an
acoustical signal generated by an external buzzer (not supplied). In normal
mode the buzzer will be on until reset. In linked mode the signal lasts only
as long as a call is detected.
Technical Specifications
Input: balanced, floating; no DC
Impedance > 20 kΩ
Frequency 20...60 Hz
Min. level 17 V
Nominal level 70 V
This card contains a call receiver for the standardized 1900 Hz call fre-
quency on OB lines. It is tuned to respond to 1900 Hz ±1 %. The receiver
can be switched either to activate an optical or an acoustical signal for the
duration of the 1900 Hz call (linked mode), or the acoustical signal can be
selected to remain activated until reset (normal mode).
The acoustical signal can be generated by an external buzzer (not sup-
plied).
Technical Specifications
Input: balanced, floating; no DC
Frequency 1900 Hz, ±1%
Impedance > 10 kΩ
Min. level –30 dBu
Nominal level +24 dBu
Supply:+15 V (5 mA); –15 V (10 mA); –6 V (2 mA)
Insulation rating 500 V