It was a similar situation when I compared the NM24 to the Eximus DP1. The supremacy of tubes when it comes to space and tonal colors shone through. I much preferred listening to the NM24’s tube DAC than to the DP1’s op-amp-based output stage. You could argue again that the NM24 gives up some detail in the process, but it’s a trade I’m willing to make any day. As I mentioned earlier, my preference was to run the tube DAC output into an external preamp or autoformer volume control. Routing the tube DAC through the internal volume control and linestage resulted in a perceptible loss of transparency and detail. If you plan to use the volume pot, a possible aftermarket modification suggested by C.C. Poon would be to replace it with a good-quality stepped attenuator.
The NM24’s most significant caveat in my estimation was its limited mastery over macrodynamics. It excelled in bringing microdynamic nuances to life, zooming in as it did on the music’s embedded passion and drama. Reproduction of female voice benefitted greatly in the process. However, its reproduction of dynamics from loud to very loud was somewhat restrained; I would rate it at best as an 8 on a scale of 1 to 10. That was especially obvious on the Analysis Audio Omega planar speakers.
One of the best investments you can make is to upgrade the stock Sovtek 6922 tube complement. I settled on a pair of JAN 7308 (graded by Upscale Audio) for the tube DAC buffer and Siemens E88CC gold-pin types for the line section, though of course many other vintage choices are possible. Expect better image focus and enhanced image separation within a spacious soundstage. Tonal color saturation was also more realistic.
Finally, getting back to the solid-state DAC, I wanted to give it one last chance after I discovered that feeding the output directly into the NM24’s line-level input was not a good idea. (The result was not pretty, harmonic textures being rather coarse and grainy.) I asked about the possibility of using a coupling transformer to limit the bandwidth as was discussed on the Monarchy Audio website. C.C. Poon suggested that a better idea would be to try Dignity Audio’s model PML2XLR Dynamic Server. This is a fascinating buffer featuring a choke-loaded 6H30 super-triode, which is coupled to a Permalloy-core output transformer. It’s not cheap at $1290 (shipping included) but it totally transformed the sound of the solid-state DAC. The end result, though not as sweet sounding as the tube DAC, yielded a big-tone balance and a 3-D soundstage. The Dynamic Server is available direct from Dignity Audio, a Hong Kong-based company that has been specializing in transformer design for over 40 years.
The Monarchy NM24 teaches us three important lessons about digital-to-analog converter design. First, there’s still plenty of audio magic left in Burr-Brown’s 24-bit/96kHz PCM1704 chip. Second, a tube buffer is sonically superior to an op-amp-based buffer, as can easily be ascertained by auditioning both built-in buffers. Third, it is much easier (i.e., less costly) to design a good-sounding DAC using an R2R chip than it is to deploy the currently ubiquitous delta-sigma type. Its sound character is exceedingly analog-like, as the NM24 sidesteps the halo of brightness that permeates the harmonic textures of so many delta-sigma-based DACs. You’ll have to look in the neighborhood of $5k in order to exceed its performance.
SPECS & PRICING
Tube DAC output/impedance: 2.5V/3k ohms
Solid-state DAC output/impedance: 2.0V/510 ohms
Linestage gain: 16dB nominal (15–19dB, tube dependent)
Linestage output: 27V (max)
Linestage output impedance: 300 ohms
Dimensions: 17" x 4" x 12"
Weight: 24 lbs.
380 Swift Ave., #21 South
San Francisco, CA 94080
MacBook Pro computer running Amarra V2.6 software, April Music Stello U3 USB Link, Sony CDR-W66 transport; Analysis Audio Omega, Tannoy Revolution XT 8F, and EnigmAcoustics Mythology M1 loudspeakers; Lamm Audio M1.2 Reference and VTL Manley reference series 100/200 monoblock amplifiers, First Watt F7 and Futterman H3 stereo amplifiers; Perla Audio Signature 50 integrated amplifier; PrimaLuna Dialogue Premium line preamplifier; FMS Nexus-2, Wire World, and Kimber KCAG interconnects; Acoustic Zen Hologram speaker cable; Sound Application power line conditioners