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Positive Feedback ISSUE45
the Symmetrical Balanced Preamplifier
as reviewed by Marshall Nack
An impressively large and heavy wooden crate arrived one day containing the NAT Symmetrical Balanced Preamp. Perhaps the factory favors oversize chipboard boxes to ensure safe transit from Serbia in Eastern Europe, where NAT Audio is incorporated. The crate reminded me of those used by Lamm Industries, which originate in Brooklyn, NY, right across the East River from where I live in Manhattan. And, as you'll soon see, the NAT reminded me of the Lamm L2 Reference preamp in sound-related ways, too.
But first let's cover some exciting design features, because the NAT is loaded with them. It is fully balanced. Many preamps make that claim; in truth, few are. For one thing, truly balanced design requires separate signal paths for single-ended and balanced inputs.
On the NAT, this means you flip the RCA/XLR toggle switch on the front panel to re-configure the machine when you change from one to the other. The Mute indicator comes on and the circuitry goes through a cycle similar to the soft start when you power-up, only it lasts about half as long, maybe 30 seconds. You witness its progress via a bank of blue LEDs on the front panel, which goes from full on to all off. Then the Mute indicator turns off and you're in Ready mode.
I have to mention the nifty volume control. Whether done via the remote or the knob on the front of the chassis, volume attenuation works by a network of relays. Not digital, or motorized, but relays, the kind that make a clicking noise loud enough to be heard from the listening seat, activating precision matched resistors. I understand that volume attenuation is "dirty," a known source of noise pollution. NAT must have determined the effectiveness of this solution, and therefore deemed it worth the extra expense and disturbance. Still, the clicking takes some getting used to. (BTW, a factory upgrade is available to install silent relays.)
The NAT is 100% tube, including power supply rectification. It is a zero feedback, all triode, full dual mono Class A design. There are 6 military grade or NOS tubes per channel. In fact, there is no solid-state inside. The NAT can make the impressive claim that the signal never sees a solid-state device.
We can expect a certain signature given this topology, right?
Start with a goodly dose of even-order harmonic distortion to sweeten up the serving. While the serving is indeed sweet—the midrange is rich like chocolate, the bottom is warm, the treble is round and smooth like honey—the effect is not as full blown as you would find in the classic valve devices of yore, like an old CJ or Marantz.
Hybrids and Solid-State units
The NAT's profile is closer to the reference-class, tube-hybrid Lamm L2 I reviewed a while ago. In both units the midband predominates and the treble is a little under-represented. The NAT's tonal balance is darker than the Lamm, its bottom-end is more abundant and warmer, and its body is more full.
These two preamps have wonderfully wholesome frequency integration and are notably grunge-free, clean and composed. (The NAT does not achieve the SOTA level of the Lamm, as occasionally it would let a treble instrument like a piccolo pop out, detached from the other frequencies. Also, it is not as composed.)
Compared to solid-state units, the recently reviewed Accustic Arts Preamp I - Mk 3 is tonally lighter and less saturated. My mbl 5011 preamp is darker. Both of these solid-state units have substantially less body and timbral richness. You'll never hear a violin with so much body from one of these.
Imagine a continuum with an older Audio Research Corp tube preamp on the right side and a vintage CJ at the other end. I'd place the NAT in the center, the Lamm a little further to the right. These preamps deviate enough from either extreme to warrant another designation, maybe "modern tube sound."
With moderate strength signals the NAT throws a somewhat hazy soundstage in the old-fashioned manner. As any particular instrument gets louder, a spotlight focused on it grows in intensity and the image comes forward. Presence and palpability are part of the territory and this is noticed with soloists, especially vocal soloists, who have a bit of a halo around them. This is hinted at, not taken to an extreme.
So, at any given time, you can have softly bowing strings in a hazy background, with the soloist standing up front, lit from within and highlighted in a tubey way. The NAT tends to fill the spaces between the notes—you don't get those "deep black silences" audio reviewers talk about. In other regards, transient quality, speed, decay and resolution are on par for a tube device at this price point.
Some Music, please
I've been listening to Joe Lovano's recently released CD, Folkart (Bluenote 3 91528 27) featuring his new group, Us FIVE.
On track two, the title track, the rhythm section is panned hard left/right. I register their presence in my peripheral hearing, but I don't particularly notice them. It's Joe's alto horn popping out from dead center that my attention is drawn to. That is because the instrument is so round, touchy-feely and lit up.
The piece evolves into a drumming face off—there are two percussionists in Lovano's new sextet. These guys are hard left/right, with nothing down the middle, and each drum set is a bit forward and highlighted. That tells me the artifact occurs all over, not just in the middle of the soundstage. When the piano takes its turn, there's no mistaking its acoustic character. The NAT nails this instrument's signature particularly well.
Speaking of staging, width on this CD was from speaker to speaker, but there was nothing beyond the cabinets. Height is good; depth is a little shallow.
I hasten to note there is no etch or abrasiveness anywhere. No unpleasant artifacts and very little tube noise is heard on quiet passages. Everything is a little rounded and… it all has that beautiful tone and timbre that only comes from filaments. The tone and timbre I'm talking about is what people mean when they say a certain component lets you hear the instrument's body, or the wood of the violin. You ain't going to get this from your solid-state preamp.
The NAT AC Coupler Grey power cord
I'd been using a TARA Labs The One power cord. Now I substituted NAT's own AC Coupler Grey power cord (MSRP $900). NAT makes a lot of single-ended tube amps. Their PC is voiced quite like I imagine those amps would be.
The NAT on NAT developed round, 3-D images, moving the marker leftwards along the continuum I spoke about above. There's more beauty—I wondered if it was too much. I would say about half my listening panel preferred the NAT PC; the others, the TARA.
The AC Coupler Grey is softer than TARA's The One, bass is less controlled and some degree of low-level detail was lost. But the musical point is communicated in no uncertain terms.
On Debussy: Nocturnes with Pierre Boulez and the Cleveland Orchestra (DG 439 896), the stage moved back behind the speakers and allowed easy access for a "walk" around it. Images were in the proper place and kept their integrity—that is, the NAT kept them stable. Their shapes are large and their borders have soft edges. Largely for these reasons, the stage is densely populated. The mood relaxed. The dynamics on the Nocturnes produced very satisfying crescendos.
On the Premiere Rhapsodie for orchestra and clarinet solo from the Debussy CD, the clarinet rises and soars above the orchestra, attaining a luminous and transcendent aspect.
The NATs dynamic range is impressive. It packs a ton of low-end weight, but it is better at big dynamics than little ones. It is more brawny than subtle.
Let's see how good those macro dynamics are.
About the largest orchestral forces demanded by a single work are required by Gustav Mahler's Symphony No. 8. I'm listening to Bernard Haitink's recording from 1971, with the Royal Concertgebouw Orchestra (Pentatone PTC 5186 166. This is an SACD; I'm listening to the Red book layer.)
It's subtitled the "Symphony of a Thousand" for good reason; in addition to the large orchestra, four choral groups are credited for a combined vocal mass approximating 300.
This is a brutal obstacle course to throw at a system. Most of the time I wouldn't even bother 'cause I know what'll result. Few preamps can pull it off. My mbl 5011 just about manages it; its bigger sibling, the mbl 6010D, wouldn't miss a beat, but now you're looking at $10.5 and $24K, respectively.
The NAT almost pulls it off. It manages to keep the several choruses in place as the music swells to incredibly powerful and densely orchestrated crescendos. It does this without breakup and without compromising quality—or, if there is some, it is covered by very soft clipping. Finally, under the heaviest onslaught near the end of Part I, stage width collapses a bit towards the middle, image integrity is compromised, and the treble hardens. Nevertheless, I'm impressed—experience with preamps at this price point led me to expect worse.
The NAT can handle anything less than that vast orchestra. It excelled with classical chamber works and jazz. Playing some first pressing Bluenote LPs through it was a match made in heaven, and made me appreciate what all the buzz (and market valuation) surrounding those LPs is all about.
A Tale of Misadventure
The performance I've described so far is using balanced inputs. However, early on I was playing a CD via the single-ended inputs and managed to alienate half of my listening panel.
With single-ended interconnects the sound moves leftward on the continuum, toward the classic CJ profile. Transients become soft and the decay lingers about. Definition suffers. This was unfortunate—the NAT's visuals and features initially had these listeners interested.
Owners should stick to balanced wires since the NAT Symmetrical is optimized for them. Fortunately, it comes well equipped with six XLR inputs (and the same number of RCAs). If you intend to use RCAs, you'd be much better off with the next up Utopia model ($8800), which is optimized for, and only provides, single-ended input.
Cosmetics and Appearance
The NAT chassis doesn't look like your standard black box. Most people found the CNC machined, aluminum chassis and thick, laser engraved, aluminum front panel attractive. It is well thought out and nicely designed. The NAT has a big footprint and is tall, about 6⅝". It gets warm to the touch, if not hot; you should allow some breathing room above it.
I mentioned the inputs above; there are also two sets of RCA outputs and the same for XLR.
The compact and heavy remote control is cut from a solid block of aluminum and provides Volume and Mute (via relays, of course).
The NAT Symmetrical Preamp is packed with impressive design features. It is dual mono and fully tubed, including power supply rectification. It can make the impressive claim that an incoming signal will exit without encountering a solid-state device. And, it is fully balanced, not pseudo-balanced like most preamps that make this claim.
There's no mistaking the filament nature of its presentation. While this is less robust than the vintage CJ profile, it is nonetheless wonderful. My wife claims I was seduced by the NAT's midrange. Now, when a wife talks about seduction, the wise husband takes note. It's true. It was that, plus the sweet treble and robust timbre that did it to me, again and again.
She, on the other hand, was put off by what she called the lack of definition, as were several other people. When I inquired, it was more a musical articulation shortfall related to the smooth transients. My usual listening panel bifurcated, with one camp saying the NAT resembled a classic Conrad Johnson machine, and the other finding it highly competitive at its price point. What can I tell you other than it's a matter of taste.
In other regards, the NAT is largely noise and artifact free, dynamic, weighty and only slightly euphonic, the latter two being less than what you would expect, the first three being more than the classic model. I would stay away from the biggest orchestral works. Anything else should be no problem. It excelled with classical chamber works and jazz.
Owners should stick to the balanced inputs. The NAT sounds decidedly better when XLR inputs are used. Fortunately, it is well equipped with six of these. Also, try out a few power cords. I liked both NAT's own AC Coupler Grey and TARA Labs The One.
The NAT Audio Symmetrical Balanced Preamp has an attractive cluster of characteristics voiced to promote musical enjoyment, rather than analysis. If that aligns with your perspective, it is well worth your consideration. Marshall Nack
Symmetrical Balanced Preamp
North American Importer