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INTRODUCTION SAM-1C
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Balancing and matching amplifier
1. DESCRIPTION :
The SAM-1C is a universal, professional 4-channel matching and balancing/differential amplifier
(instrumentation amplifier) in ironless circuit technology for use with the highest demands on sound quality.
Asymmetrical "home recording" and PC inputs and outputs and hi-fi equipment signals can be matched to
professional balanced or unbalanced studio equipment inputs/outputs. Level adjustments from -10 dBv to +6
dBu and vice versa as well as signal distribution is also possible, depending on the configuration.
The SAM-1C is the successor of the SAM-1B/SAM-1B with the additional possibility to mix signals. The audio
signal quality, such as common-mode rejection (unbalance attenuation), THD distortion, headroom and
overall dynamic range, has been further improved.
Compared to the SAM-1B, the SAM-1C version also has a precision switching power supply for operation with
all mains supplies worldwide with operating voltages of 80..260 V and frequencies between 45..440 Hz. The
mains cable of the SAM-1C is detachable.
The SAM-1C can enable the following functions simultaneously :
1.
a high-impedance signal becomes low-impedance (impedance conversion).
2.
an input signal can be amplifieda balanced signal becomes asymmetrical/attenuated
3.
a balanced signal becomes asymmetrical
4.
an asymmetrical signal becomes symmetrical
5.
2 balanced signals can be summed (mixed) (stereo > mono)
6.
"hum loops" between unbalanced units can be eliminated
7.
switch-on or switch-off crackles of a sound system can be eliminated ("power-down" mute)
8.
configurations as balancing and distribution amplifier internally possible
1.1 Mode of action :
To ensure that the interference voltages induced or influenced on a line cause as little interference as possible
in an input of an audio control system connected to this line, this input must be "symmetrical to earth", i.e.
the two resistances measured between each of the input terminals and earth must be equal in magnitude and
phase. The induced interference voltages, which are equal in magnitude and phase on both conductors, then
cancel each other out in their effect with a symmetrical input and have no influence. If the symmetry is not
exact, however, the induced voltage is not completely cancelled out and a residual interference voltage
remains in the subsequent transmission path.
The balanced input stages SSIM-04Mc of the SAM-1C achieve a typical suppression of balanced interferences
at 1 kHz in the ratio 1 000 000 / 1 approx. - 120 dB ! This extremely high symmetry also makes it possible to
optimally suppress interference due to different ground potentials. This also applies to applications with
otherwise asymmetrical cabling.
Auto-Mute :
The outputs of the amplifiers in the SAM-1C have a "power-down" mute relay in the output. This ensures a
largely crack-free switching on and off of the unit even after a sudden drop or failure of the supply voltage.