Awesome Class D for the Sierra LX (review of my choices)

[piaresquared]

I bought my Sierra LX speakers in January. Now that they are settled in and sounding good, I thought I would share my thoughts on a cheap and cheerful initial setup and then the present, much nicer configuration.

Initial Configuration

I initially set up the LXs with a WiiM Amp, which is just 60W maximum and does not have a flat response at frequencies above about 8 kHz. I’ve owned a Pass Labs XA25, Benchmark AHB2, Jolida EL34 tube, and GaN Class D amps with previous, bigger systems, so I did not expect much from the WiiM Amp. However, I was very surprised at how musical and detailed it sounded and how much bass it could provide in a small to medium-sized room (about 12x18).

I did try a pair of GaN Class D amps (from Class D audio) running from a WiiM Pro Plus, but the excellent tweeter of the Sierra LX revealed too much of the high-frequency grunge in that setup (probably due largely to the digital volume control on the WiiM Pro Plus and its poor analog stage).

I would definitely recommend the WiiM Amp with the Sierra LX if the total system budget is ~$1700. The only caveat is that I do have a ~$3,300 power conditioner (Puritan PSM156-XX) that was probably going a long way to clean up the AC into the WiiM Amp. I did not try the WiiM Amp without the Puritan, so I can’t confirm how much the Puritan contributed.

Bigger and Better Things

While I was enjoying the WiiM Amp, I expected that the Sierra LXs would benefit from more headroom and control. I started investigating the recent iterations of class D amps from Purifi and Hypex. I already own a pair of GaN calss D monoblocks as mentioned above, but I haven’t been convinced by their handling of high frequencies. I listen to a wide range of music, including classical and acoustic music, that needs well-reproduced harmonics.

Bruno Putzeys developed the NCore Class D amps for Hypex, and then he went on to develop Eigentakt class D amps with Purifi. Since I already had a GaN amp and had concerns, I thought I would look into the NCore and Purifi. I ran across a ~2 hour listening test on Youtube using a pair of Schoeps studio microphones: https://www.youtube.com/watch?v=NdZFAWe1Nxo

The differences in tonality and timbre of the amps used in the test are easy to hear. In addition, the newest Hypex amp, the Nilai, was amazingly good at preserving the harmonics in piano while retaining the detail retrieval and bass control of the Purifi amp. The Purifi amp seemed to push the bass more forward, and it seemed to present the pieces of the composition with excellent detail while tending to lose the flow and coherence of the whole.

That same YouTube channel, Alpha Sound, also posted a comparison of the Hypex Nilai with a Yamaha A S2200, in which the upper midrange provided by the Nilai sounded more open and detailed than the Yamaha in a way that conveyed the emotion in the human voice more effectively.

After reading more on the technical advances in the Nilai (primarily the use of additional noise reduction in the power supply and an additional loop of noise reduction in the amp module), I decided to order an assembled Nilai stereo amp kit from VTV Audio. I had them install a set of WBT Cu speaker binding posts as well.

To complement the Nilai amp, I bought an Eversolo DMP-A8 to serve as streamer, DAC, and pre-amp. This new front-end setup is ~$3500 compared to the $300 of the WiiM Amp. The Puritan power conditioner and Puritan power cables are running things, so that does add another ~$4200 in equipment, to be fair.

The New Sound

Everything has had ~140 hours of burn-in, and the sound is amazing. The Sierra LXs are very articulate in the midrange, upper midrange, and treble (besides being excellent in the bass). The Nilai provides the decongestion and natural timbre and harmonics that the LXs are able to convey; it has transformed what I am hearing. Massed strings and busy symphonic passages are now open and textured without the strain I’ve often heard in previous systems. I am now able to follow individual instruments in complicated passages, and their timbre is very naturally portrayed. Vocals are also more expressive and realistic, and this doesn’t come at the expense of conveying the weight and speed of electronica or the grunt of Zeppelin II. Finally, the Nilai is giving the LXs enough power and control to open up the bass in the very lower reaches and to provide texture and timbre there that I wasn't hearing with my previous speakers (open baffle with two 15" mid-woofers). I will, at some point, swap those large floor-standers back in to see how they sound now, but they were not as good as what I'm hearing in the midrange and treble from the LXs, so I don't have an expectation that they will be preferable overall.

Given that the LXs will benefit from class D power, I think the Nilai is a terrific choice. I have not heard the very latest Purifi 1ET9040BA amplifier module or the AGD GaN amps (which are GaN amps designed for audio rather than the repurposed GaN chips that were not designed for audio), so there are certainly other viable options. But for ~$1250 (or $1500 in my case) the Nilai stereo amp kit is seriously good. The less expensive Eversolo DMP A6 would likely be excellent as well, so a full system of very articulate and musical sound could be put together for ~$3500. If I had had something like this 30 years ago, I would have saved a lot of money over the decades!