Lyngdorf SDA-2400 Amplifier Review

If cool, quiet operation in an amplifier is important to you, the SDA-2400 deserves your attention.

Have you noticed lately that Class D amplifiers are on the rise in the audiophile world? A common misconception about them is that the “D” stands for Digital. It does not. These are switching amps that use a modulator (usually a MOSFET) to convert the input signal (analog or digital) to a PWM (Pulse Width Modulated) signal. It wasn’t too long ago that many Class D amps suffered from increased THD, dead time and shoot through, but most of those issues have now been overcome.

These new switching amps can rival the best Class A/B amps for shear power and beat them handily in efficiencies that exceed 90%. Lyngdorf has designed the SDA 2400 to be a highly dynamic switching amplifier with extremely low and linear distortion in the full frequency audio range. Boasting 200 watts into 8 Ohms, I think they have succeeded in their design goals.

Based out of Denmark with a USA office in LA, Lyngdorf has been known for audio components that are recognized worldwide as some of the best high-performance digital audio products available. Their R&D has developed Intersample Clipping Correction to restore clipped signals back to their original shape and a digital room correction that is built into their TDAI-2170.

The output stage of a switching amp is either fed a digitally modulated signal of PCM-to-PWM, or an analog-to-PWM. The SDA- 2400 is of the later analog type. The modulator converts the analog input signal to a PWM carrier that operates at an extremely high frequency. The magnitude of each PWM is described as width, as opposed to height, as in a PCM signal. The incoming signal is up-sampled to a PWM signal, which in the case of the SDA-2400 is 390 kHz.

Finally, the signal is fed to the H bridge output stage where the fixed 390 kHz frequency passes through a 12dB low pass filter at 50 kHz, which gets rid of phase problems in the audible range (effectively, any frequency above 44.1 kHz).The output filter coils used by Lyngdorf are ferrite cores which give the signal both low distortion and excellent linearity. The switching speeds are controlled by the latest technologies in MOSFET designs. (I will not bore you with a MOSFET design lecture. GOOGLE it).

This excellent switching performance increases the overall efficiency of the amplifier and greatly reduces the heat production that Class A/B amplifiers suffer from. Class D amps are often <90% efficient. The energy does not get converted to heat. Generally, Class A/B amps are around 50-60% efficient. Class A is around 30%, which is why you can fry an egg on them after an hour of music listening.

Thus, you will notice that the SDA-2400 does not have any ventilation holes on the top, bottom or sides. This sealed design also helps keep dust out of the component. After many hours of use, the SDA-2400 never even became warm to the touch and we know that heat is the mortal enemy of electronic gear. Even when idling, the “On/Off” nature of the MOSFET is optimized to keep distortion to a minimum.

Nothing is perfect, though. The biggest cause of MOSFET distortion is the switching timing, the On/Off speed, or more precisely the time the circuit is instructed to turn On vs. when it finally does turn On. Lyngdorf selected drivers that have as low as a 20ns delay and these are matched within 1ns between On/Off. If a switch stays On during a Off cycle, you have shoot through, which will eventually destroy the circuit.

If it doesn’t turn On/Off precisely, you can get distortion and timing errors. The SDA-2400 uses much less feedback on the circuit as other Class D amplifiers might. The use of negative feedback helps reduce the amount of distortion from less than ideal components. Ultimately, the noise floor is very low and linear in the audible range. Placing my ear up to my speakers with the music paused revealed absolute silence without hiss from my tweeters. Silence is indeed, golden!

Finding room for a new component is sometimes tricky in my listening room, but because the SDA-2400 was relatively thin and light, I decided to set it directly on top of my Emotiva UPA-100 mono blocks. As you can see in the picture.

The SDA-2400 can accept Toslink, digital coaxial, RCA analog connectors as well as a balanced analog input. There is a selector on the back panel that permits the selection of one of those choices. You can leave the amp in standby with the option of an audio input signal “waking” the amp up, having a 3.5 mm trigger or leaving the amp On all of the time. There is no On/Off switch on the front panel, but there is one on the back panel.

In standby mode, a small white LED blinks slowly (like my Mac Mini, actually). When the amp is On, the LED stays solidly lit. My pre/pro does not have a digital out, so to test the amps digital input I used my Oppo 103 to connect to it via a coaxial connector. If you do this, your digital device must have a volume control. Make sure the volume is low or off when you first power everything up and work your volume up till you get to comfortable sound level. I learned the hard way… so you don’t have to. I ultimately settled for the analog inputs via my pre/pro. It offered me room correction, DSP and bass management prior to amplification, but at least you have some options. I used the audio signal input to turn the amp on. I noticed over time that the amp did not always spring into action when I started with soft music. It took the relay a few seconds to detect a signal and the actual turning on process took another 2 seconds, sometimes clipping the beginning of my music selection. My other option was to leave the amp on all of the time, which I do not like to do. The amp will automatically go into standby mode after about 20 minutes of no audio input signal. As long as your speaker cables are wired in-phase, you are ready to go. For the record, my interconnects are Kimber PBJs and speaker cables are Zu Audio Julians. My main speakers for this review are Revel F12s.

I have heard from some critics that switching amps have to use harsh filters to remove the PWM carrier and that this makes them sound un-natural and un-musical. Lack of linear output is another complaint, which can be true in other designs. Others argue that the bass is flabby (ironic, since many powered subs use a switching amp). Fortunately, that was not what I found with the SDA-2400. I ran music through it that would have revealed any issues with noise or distortion. I was especially curious to find what would happen to the delicate decay of an acoustic instrument.

It was stone quiet in the silent places. This was made all the more startling when inky silence was followed up with the full orchestra in the next movement. Solid bass from the brass and timpani were all there. The tinkling triangle could easily be heard above the fracas. Imaging was very good as well as depth of the sound stage. I was impressed with how big and solid the sound was.

Orchestral music is one thing, but the human voice is another instrument altogether. Dawn Upshaw’s soprano was beautifully rendered with the SDA-2400. Hampson’s baritone was natural and resonant as it should be.

Squire’s bass line was deep and taut as it leapt across Southside of the Sky, Anderson’s distinctive tenor rang out clearly above the band while Rick Wakeman glided through all of the glorious chaos with his keyboard. Percussions sounded impactful and the Wilson mix had it placed perfectly in space, being much more up front than the recessed 2002 mix. I know, how does a guy that listens to mostly classical music enjoy Yes? I find their music to be quite “classical”, I guess. Wakeman is a classically trained keyboardist. Listen to Cans and Brahms, or Howe’s acoustic guitar in Mood for a Day. Good musicianship is good musicianship. But I digress. Bottom line, the Lyngdorf can rock and roll.

The bass notes are full and resonant, the treble sparkles and the hammers softly hitting the strings are almost palpable. The SDA-2400 reproduced the piano sound pitch perfectly. All of the detail I was expecting was there. More importantly, the sound was natural and the final decay of the fading strings was not harsh or granular. A true test of the quality of an amp is not only how loudly it plays, but often how well it sounds when being delicate, just at the threshold of hearing. The SDA-2400’s sound was musically satisfying. The inky dark background was just perfect for music rendition. I can’t imagine a music lover not liking the sound of the Lyngdorf SDA-2400. In my few months of auditioning this amp, I never felt I was missing anything in sound quality. It kept its composure no matter what music I played through it.

THE LYNGDORF SDA-2400 is one of the Quietest Amps I Have Ever Reviewed.

The Lyngdorf SDA-2400 answered many of the questions I had about Class D amplification. Would I replace my current mono blocks with this amp? I am inclined to think that I might. It has the same amount of dynamic power as my monos, the sound quality is superb and the low noise floor is remarkable. Stereo separation is also excellent with a wide and deep sound stage. On the other hand, I got my monos for a bargain basement price. If I were starting out again with a nice 2 channel setup, I would certainly give the SDA-2400 a close look and listen. It is efficient, musical, runs cool as a cucumber and has plenty of dynamic power on tap. It took me a whole 5 minutes to setup and has a sleek low profile design that exudes quality. Whatever your personal opinion about switching amplifiers has been in the past, get ready for the future. Class D has finally evolved into an audiophile product with the Lyngdorf SDA-2400. With more manufacturers using Class D amplification these days, it might be time to for you to consider switching. The Lyngdorf SDA-2400 will change the way you think about Class D amplification