Lyngdorf Audio is the successor of Tact Audio ApS, which, under the leadership of Peter Lyngdorf, has held a leading position in the field of digital sound amplification since the late 1990s. The company has one of the largest research centers (more than 30 engineers) among Scandinavian manufacturers of high-end equipment. SDA 2175 is an analog-digital amplifier of the highest quality. The output stage uses a pulse-width modulation system with a patented switching speed optimization technology. This is an integrated amplifier in which analog sound circuits are combined with digital control. The signal path is the shortest. There are no relays and fuses in the output stage. All protection functions are implemented using a proprietary control scheme. The built-in software can be updated directly via the Internet. The amplifier provides a low level of any kind of distortion and an unprecedentedly high level of sound quality with a very small feedback depth - significantly less than that of conventional class D amplifiers. A carefully thought-out design distinguishes all elements of the amplifier - starting with the power input with a low-noise toroidal transformer Holmgren. SDA 2175 uses a fully symmetrical topology. If the switched input signal comes from a symmetrical source, the symmetry of the signal is preserved all the way through the amplifier to the pulse-width modulation conversion stage. This guarantees a much better signal / noise ratio than in the vast majority of known class D amplifiers. Only the highest quality elements are used in the output stage, for example, exclusive polypropylene capacitors and linear ferrite elements are used in the output filter. In combination with other technologies, this provided the SDA 2175 with a low level of distortion throughout the frequency range. Therefore, the sound of any source will be reproduced as naturally as possible. The amplifier is housed in a strong aluminum housing. Aluminum is a non-magnetic material capable of protecting the equipment from high-frequency radio interference. Even the bolt that fastens the power transformer is made of non-magnetic stainless steel. Such a design not only has a pleasant appearance, it is strong and protects all electronic elements from vibration.

Design features of the amplifier

• Balanced (symmetrical) and unbalanced inputs - switchable.
• Balanced circuitry from input to output (a signal from an unbalanced input is converted to a balanced one).
• Absence of transient capacitors in the signal path (amplifier cascades are connected by direct current).
• The original circuitry of the pulse amplifier is protected by patents (less deep overall feedback is used than in "normal" class D amplifiers; also the PWM converter of the amplifier operates at a constant and rather high frequency, 400 kHz).
• Absence of relays and other executive devices of the protection system in the path of the signal (the protection system of the amplifier and AC is directly controlled by the pulse output stage and simply stops the passage of pulses by de-energizing the output terminals).
• The power source uses a large toroidal transformer manufactured by Holmgren.
• The amplifier is characterized by high efficiency and, accordingly, low heat generation, and lowering the operating temperature of electronic components helps to extend their service life and increase the reliability of the amplifier as a whole.
• All electronic components and printed circuit boards used are of high quality.
• The body of the amplifier is made of non-magnetic materials: all panels are made of aluminum alloys, fastening elements are made of non-magnetic steel.
The sound provided by this amplifier can be characterized as: tonally balanced, neutral, accurate, with high detail and excellent dynamics. The amplifier perfectly controls various acoustic systems, even the most "tight".

Specifications

Output power, 1 kHz, 0.1% THD + N: 2 x 200 W (8 ohms) 2 x 375 W (4 ohms)
Nominal load impedance: 4 - 8 Ohms
Frequency response: 0.3 Hz - 33 kHz (-3 dB, 8 Ohms); -0 dB / +/- 0.2 dB (20Hz-20kHz, 8Ω)
Output Impedance: 0.035 Ohms (20 Hz - 1 kHz)
Output Impedance: 0.4 Ohms (20kHz)
THD + N, equivalent level: 0.004% at 1 W (8Ω); 0.006% at 1 W (4Ω); 0.1% at 100 W (8Ω); 0.07% at 275 W (4 Ohms)
Signal / noise ratio, equivalent level: 113 dB (control 200W / 8Ω)
Channel separation: 84 dB (1 kHz, 220W / 8Ω)
Maximum output current: +/- 40 A
Network voltage range: 200-240 V AC. current, 50-60 Hz (230V)
Power consumption: 1.5 W (standby mode); 35 W (on, no output signal); 116 W (2x37.5 W / 4 Ohm); 820 W (2x300 W / 4 Ohm)
Width: 450 mm
Depth: 355 mm (with speaker connectors)
Height: 100 mm (with supports)
Net weight: 13 kg
Gross weight: 16 kg