Power amplifiers stereo — Lyngdorf SDA-2400

The SDA-2400 comes from the Danish company Lyngdorf Audio as a stereo power amp, listed at USD 2,400 in the American market. Lyngdorf positions it for stereo systems, as the power stage behind its own processors, or as an upgrade to an existing amplifier chain. It also accepts digital signals directly, so a streamer or transport with a coaxial or optical output can be connected without a separate DAC.

Key specs that matter

Each channel produces 200 W into 8 ohm and 400 W into 4 ohm. Four inputs are fitted - one single-ended RCA, one balanced XLR, one coaxial digital input accepting up to 192 kHz and 24 bit, and one optical input limited to 96 kHz and 24 bit. Frequency response is within 0.1 dB from 20 Hz to 20 kHz. THD+N is 0.004% at 1 W into 8 ohm, 0.006% at 1 W into 4 ohm and 0.02% at 100 W into 8 ohm. Signal to noise, A-weighted, measures 117 dB against 200 W into 8 ohm, and channel separation is 96 dB at 1 kHz at the same output. Lyngdorf gives the dimensions as 45 x 7.3 x 36 cm, and the weight is about 6.5 kg.

Engineering and use context

Its output section relies on pulse width modulation with a patented switch speed optimisation, running at a fixed 390 kHz switching frequency with minimal feedback control. Analog signals are converted directly to PWM at that carrier frequency. The output filter uses ferrite core coils forming a 12 dB low-pass filter at 50 kHz, and the MOSFET drivers have a 20 ns delay matched within 1 ns between devices. Idle consumption is around 25 W and standby draw is 0.35 W, so the unit can stay powered in a rack without much heat. Every input has signal detection, and the amplifier can be set to remain on permanently or to switch on when a signal appears. A 12 V trigger input and output allow control from a preamplifier, and several SDA-2400 units can be daisy-chained so that one trigger wakes a whole stack. The case is anodised aluminium in matte black, and rack mounting ears come with it.

Pairing

The balanced and single-ended analog inputs suit any preamplifier with a volume control, while the digital inputs make most sense after a source or processor that sends a variable-level digital stream, such as a Lyngdorf processor. Given that power doubles as the load halves, low-impedance floorstanders are within its range, and two units can be linked by trigger to bi-amp a pair of speakers.

Alternatives

An older stereo option from Lyngdorf is the SDA-2175, with the same per-channel power and fitted with a 650 VA toroidal transformer.