REVIEW: Lyngdorf TDAI-2170 Stereo Amplifier
The Lyngdorf TDAI-2170 is an audiophile level stereo amplifier that does not shy away from using digital technology to achieve its high quality results.
Indeed, digital is at the core of this unit because the stereo amplifier section is operates in the digital domain. It’s rated at 170W per channel into 4Ω. It includes a DSP to allow the system to adjust the sound for room correction and to set crossovers.
The front panel is minimalist: with a display on the left, a selector knob towards the centre, a large volume knob to the right and to its right a small Standby/On key. At the rear are the inputs along with sturdy binding posts for one pair of loudspeakers. There’s a hard wired power switch at the rear as well.
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In standard trim (but see Options below) it comes fitted with two analogue audio inputs, two coaxial digital audio inputs and four optical digital audio ones.
Options
One of the nifty things about this amplifier is that it can be optioned up with additional inputs and outputs. There are three modules available.
First, you can add more and different analogue audio inputs. The ‘High-End Analog Input Module’ adds three pairs of RCA inputs and one pair of balanced XLR inputs, all analogue as the name suggests. Since the amplifier is digital, this module’s inputs must be converted to digital. Rather than using the main analogue to digital converter, it has its own on-board AKM-AK5394A ADC. This has a rated dynamic range of 123dB.
When dealing with digital sources, with this amplifier it’s better to use the digital inputs rather than the analogue ones, since that eliminates unnecessary digital to analogue to digital conversions. So the second module is for that other digital mainstay: HDMI. There are four inputs and one output. Their audio support is for PCM up to 192kHz, 24-bit and Direct Stream Digital in both standard forms (i.e. DSD64 or 2.8MHz) and double-rate (i.e. DSD128 or 5.6MHz) both in stereo. They do not support the various versions of Dolby and DTS sound, but your Blu-ray player should be happy to convert these to suitable PCM. The HDMI output supports the Audio Return Channel for use with sound from a TV. They passed through the video without processing, aside from overlaying the volume and input setting when these are changed. While they handled 3D video, I could not get them to pass through 4K video signals.
Finally, there’s the streaming USB Input Module. This has a single connection: a USB Type B socket and it is for connecting to a computer. It acts as a USB Audio 2.0 device, supporting PCM up to 384kHz and 32-bit, as well as DXD, DSD64 and DSD128. DXD stands for Digital eXtreme Definition and is, basically, PCM at 352.8kHz and 24-bit. It was developed because for technical reasons DSD is a pain in the recording and editing suites. DXD was originally intended to be converted to DSD as a final stage, but is higher resolution that both DSD64 and DSD128 so there’s potentially value in skipping the conversion and decoding it directly.
The review unit was loaded up with all three of the optional modules.
Setting Up
Most of the setup is straightforward. Just plug your stuff in. But there are a few things you might want to pay attention to. First, if you’re using a subwoofer with your speakers, the unit is extremely flexible. You can set up a low pass filter to the subwoofer, complete with your choice of filter crossover and style (Butterworth, Linkwitz-Riley, digitally implemented, along with the filter order or steepness). And a matching high pass filter to the main speakers, so that they aren’t wasting their capacity on deep bass with which they can do little.
The unit also includes a room correction system called ‘RoomPerfect’. This is designed to identify and correct defects in the sound produced by your room. A microphone and stand are supplied with the amp to facilitate this. You start with the microphone in the main listening position, and the amp produces the most Sci-Fi sounds imaginable. Then repeat this with the microphone in a number of different random positions throughout the room until the amplifier indicates it has achieved a ‘RoomKnowledge’ of at least 90%, preferable 95%. This required four additional measurement positions in my room beyond the prime one.
When playing music, you can select ‘Global listening’ or ‘Focus listening’ as the playback mode. The former gives a general optimisation for the room, the latter for the prime listening position. There are also a number of EQ modes available.
The set up does not include an on-screen display, even with the HDMI module installed. The menus are shown in the front panel display. During playback, the input setting and volume, global/focus and EQ status are visible on the display.
Performance
The performance of this amplifier with a range of loudspeakers was exemplary. It exercised complete control over them – even my very low impedance floorstanders –had enormous reserves of power and simply delivered smooth, dynamic and precise stereo music.
The RoomPerfect settings seemed to do their stuff with no noticeable degradation of the sound quality, as you’d expect from high quality digital signal processing. Nonetheless the purist in me settled on the ‘bypass’ setting, which left the signal in its original state. The ‘Focus’ setting brought the stereo image a little closer to me than I’d prefer. With my favourite speakers I preferred the increased image depth delivered in bypass. ‘Global’ did a decent job of balancing the sound to inoffensiveness throughout the room, except of course close in to the corners.
A nice feature is that the arrow cluster on the remote allows you to switch easily between these three modes, and also to select the EQ setting (there’s a graphical representation on the front display).
Initially I was unimpressed with the input selectors, especially given the number of inputs the unit had with all the modules installed. However you can go into the settings and disable all the inputs not in use, so the cycling through and up/down functions become much more efficient.
The volume control on the front panel was glorious, rotating with utter smoothness and with a nice feeling of momentum. The push buttons on the remote, though, were overly precise, changing the level in 0.1dB increments. The volume adjusts quite quickly enough if you hold it down, but for those slight adjustments where you might normally stab the volume button once or twice for a 1dB change, this one requires ten presses.
Being digital, the amplifier runs very cool. Even after a couple of hours of solid music at very room-filling levels, the enclosure was only slightly above room temperature.
Speaking of volume, the unit also starts with a particular volume setting, rather than the last one you used. You can set the default. Still, I prefer a system that just goes with the last setting.
The Windows 8 USB driver supported the standard Windows Direct Sound format (suitable for mixing in with system sounds) and both event and push style WASAPI, which allow the music software to communicate directly to the Lyngdorf driver and thus provide bit perfect performance. However, unusually, there was no ASIO support. Consequently I could not supply the unit with DSD this way (an ASIO driver is required) from Foobar2000, nor DXD. Perhaps there’s a workaround, but Lyngdorf gives approximately zero information about how to use this module to best effect (‘start playing music on your computer’ is all it says).
Anyway, Foobar2000 consequently converted both DSD and DXD to PCM. The ‘Info’ panel on the amp showed the DSD as 88.2kHz PCM and the DXD as 352.8kHz PCM.
I tried running some frequency response tests using the analogue audio outputs and digital signal inputs, both via optical and USB and the unit presented some difficulties. In particular it seemed to apply a soft-clipping algorithm to the test signal peaks, bringing them down a couple of decibels from their natural peaks. Investigating further, I found that a process called ICC (for ‘Inter-sample Clipping Correction’), which adjusts headroom to avoid clipping, was engaged. Switching this off, though, seemed to make matters worse.
There was no evidence of this at all on listening through the main speaker outputs, so I’m not at all sure what was going on there. Given that I can’t vouch for the reliability of the measurements, they aren’t worth mentioning.
Conclusion
What I can say is that the Lyngdorf TDAI-2170 stereo amplifier is a high performance, fine sounding unit even without employing its extensive digital technology to optimise your listening room.
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