POSITIVE FEEDBACK ONLINE - ISSUE 34
NVS-003G OTL amplifiers
as reviewed by Jeff Parks
It seems these days that the high-end audio market in the United States may be slowing down due to the lack of start-up audio manufacturers coupled with the decline of traditional "brick and mortar" specialist audio retailers. On the other hand, the Asian market it quite robust. Over the course of the last two years or so, I have seen several new Asian companies sprout up and give it a try in the US market. While some of these manufacturers offer great value and sound for the all mighty dollar, there are few of these manufacturers who try to obtain "true" high-end purist sound by creating the best possible product they are capable of designing. One such manufacturer attempting to accomplish this task is Navison Audio.
High-end audio from where?
High-end audio gear from Vietnam…? Yes, that was a surprise to me as well. Why? Maybe it could be due to my own prejudice in discounting Vietnamese designers as a force within the high-end audio market due to what appears to be a freshman entry, or maybe it is due to recently accepting China as producer of reasonably quality priced high-end audio products.
Navison Audio is headquartered in Ho Chi Min City, Vietnam where their products are manufactured and assembled. Serving the U.S. market is a small support staff in San Jose, California. This is also the location of the North American corporate offices for Navision Audio headed by President and CEO Ben Nguyen. For those of you who are unfamiliar with Navison Audio, Ben and his engineering team have been designing and selling high-end audio products since 2000 for the vigorous Asian audio market. Upon completing my cursory investigation into the NVS-003Gs, $8900 per pair, the 75-watt per channel monoblocks are priced in a market that is currently dominated by the likes of Atma-Sphere Audio, Joule Electra (both top OTL designs), and my favorite pentode (non-OTL) design the Audio Research VT series, and the E.A.R. 890. This is tough company to keep in an ever competitive and sometimes ruthless high-end audio market. Ben claims he is up to the task.
No matter the perspective I look at this, it has been more than three decades since the United States tried to stop communism from spreading in Asia by fighting a "hot" war in Vietnam. A lot can change in 30 plus years as both nations are now looking to one another as business partners, as opposed to political enemies. Case in point, look how many United States high-end audio manufacturers have recently changed their business model—as they try to keep up with today's global economy—by keeping costs down with outsourcing of skilled labor jobs to Asia. Now that Vietnam appears to have completely recovered from the "Ten Years War", coupled with opening of economic doors between our two countries, Vietnamese products are starting to trickle down into the US consumer market. Once again another Asian company is exporting high-quality, reasonably priced, audio gear due to cheaper skilled labor costs in Asia for Navison Audio.
To tell you the truth, I was very pleased and highly interested with what Navison Audio could offer after I visited their website. It is hard not to notice how drop dead gorgeous their amplifiers and preamplifiers are upon first glance. Navison Audio's gear, with their mesmerizing beauty, is true audio jewelry. Not only could I hardly contain myself, my wife even made a comment as to how striking Navison Audio's gear was to the eyes. That being said, I immediately got on the phone with Ben at Navison Audio to acquire a review sample. Who could blame me for fantasizing over the NVS-003 OTL monoblocks with their 24k gold plated copper top plates, Barian Kingwood framing, Cardas Gold over Rhodium RCA input posts, Audio Note Rhodium binging posts, Auricaps, Jenson paper-in-oil caps, Mundorf power capacitors, Nichicon filter capacitors, WBT solder, and Ceramic tube sockets? These amplifiers are a "tweekers" end-of-a-dream with all of the tweaking having already ready been done in stock form. However, what was most striking to me was the drop dead beauty in terms of the quartet of triple-nipple 6C33C-B triodes flanked by a set of three 6SN7 tubes. The NVS-003G OTL is truly a sight to see—especially at night!
Getting the goods!
Shortly after my conversation with Ben I received a pair of NVS-003G OTL monoblocks directly from Vietnam. Since my pair came across the Pacific Ocean, both amplifiers were crated in order to protect them from the rigor of intercontinental transportation. Bearing in mind the wooden crates, for which each amplifier was housed, are very large and cumbersome, and coupled with 003s awkward weight, I felt it would be best to un-box each amplifier in my downstairs garage and then hand carry each to my upstairs soundroom. Often I have received damaged gear in the past via various shipping companies who move packages in and out of their facilities faster than a hyperactive squirrel. With the Navison 003s, I was pleasantly surprised to notice the pristine condition of my review samples. I am positive this was due to the shipping box with the well designed internal packaging. Kudos to the engineers at Navison!
Getting the amplifiers up and running was a snap. In my examination of the short, but still very descriptive owner's manual, I realized all I needed to do to get going was to install the tubes using a pair of gloves. This allowed me to place each tube in their respective locations without any incriminating fingerprints. No biasing the tubes, or placing a specific matched pair in a specific location—just place them in the amplifier and you are ready to go. One other thing I noticed was the beautiful engraving on each NVS-003G. The font chosen gives the 003 a sense of class that exalts it as a fine piece of serious audio gear. Unfortunately, due to an apparent loss in translation, instead of saying Triode Tube Handcrafted Amplifier, the engraving states Triode Tube Manual Amplifier. Apparently, the word in Vietnamese for handcrafted translates to manual. From what I understand Ben is aware of this error and is taking action to correct the problem in future runs of the 003. In the meantime, for those of us who own these "manual" amplifiers, it can serve as a good story starter. Since I love to talk, this is no biggie. As many of you know, misprints on audio gear are rare, but it does happen.
No biasing ability?
No biasing? What is up with that? Since all tubes age over time, doesn't it become necessary to re-bias the tubes over their lifetime? In contacting Ben, he states that 1) this is not necessary for the 6C33C tube (actually it can be done, but the process is quite time consuming, not necessary, and difficult to pull off for the novice), and 2) it was a safety issue to prevent premature failure due to some users not properly biasing their amplifiers. He has the amplifiers biased at a modest 110mA, so that when the tubes start to give up the ghost at or near 2000 hours of use, all one has to do is contact Navison Audio for a set replacement tubes—at the reasonable price of $200 for both amplifiers—and you are up and running. Once the tubes are placed in the amplifier, the 003 will auto bias to adjust to the new tubes, and you are good to go.
As to a safety issue, I do have to agree with Ben since I have seen many an amplifier blow up a tube (sometimes rather dramatically) due to the end user over biasing the tubes during adjustment. Heck, I once blew up at tube (rather dramatically I must add) when biasing an ARC amplifier. The tube blew due to its old age and my over biasing it. This resulted in me sending my ARC amplifier back to Minnesota for repair where the blown tube damaged one of the main transformers—a $1000 repair. To ARC's credit and outstanding customer service this was done under warranty—wow! Now that I am much more familiar with biasing tube amplifiers I know this problem will never happen again since once is enough for me. But, for those of you who are new to tubes, maybe Ben has the right idea in preventing the end user from biasing the amplifier. Just some food for thought.
No output transformer—hummm….
Describing the design philosophy I thought it would be best said by allowing Matthew Santa Maria (Navison Audio's US Marketing Director) to elaborate on this topic. "My first experience with a Navison amplifier was the NVS-003G. Frankly, it was the reason I joined the company. After owning several OTL designs and having kind of a love/hate experience with this approach, I was prepared to enjoy the transparency this circuit brings to the table. However, I was unprepared for the way the Navison amp makes music in such an organic way. This cemented for me the special nature of the Navison approach where I am proud to have joined their team. Match the NVS-003G with the appropriate loudspeaker and you will experience a flow and immediacy in your playback system that will change the way you listen to recorded music."
Matt is right good in that OTL designs can bring immediacy to the music that is so realistic it can almost be spooky. Those of you who are familiar with OTL amplifiers know they have a singular sonic signature due to directly coupling the speakers to the output stage of the amplifier, thus eliminating the output transformer. This direct coupling can result in a sonic purity that truly must be heard to be completely understood. When it comes to mid-range on up through the upper frequencies, OTL designs are at their best. This relationship results in a speaker-amplifier coupling that is tighter and more responsive resulting in better clarity of sound with increased micro-dynamic delivery without compromise to macro-dynamics and dynamic headroom. In other words, OTL amplifiers sound almost solid-state like in their speed as compared to other tube type circuit designs while maintaining tube sonic purity. So, the question lies can we have our cake and eat it too—meaning achieving a solid-state like speed and snap while maintaining the musicality of tubes? My answer to that question is maybe yes, and maybe no!
Or better yet, I can answer that question with another, "Are OTL amplifiers the panacea to your audio woes?" That really depends what your "audio" agenda is, and how the 003 falls into that plan. Like I said above, many proponents of the OTL design believe that by eliminating the output transformer, one is able to achieve a coupling with the speaker that normal output transformer designs only dream of reaching. And most engineers will agree that the weakest link in any amplifier's design is the output transformer. At low frequencies the output transformer's inductance steals current away from the load, and at high frequencies its stray capacitance, leakage inductance, and high frequency copper losses add up to attenuate amplitude that can introduce major phase shifts--a problem that has troubled engineers for decades. So no output transformer, no problem.
On the other hand, can we have it all when one has to bear in mind the bane of all OTL designs is how to drive today's demanding dynamic speakers without robbing the amplifier of dynamics and bass slam? Most people know that impedance issues are troublesome for many OTL designs. OTL amplifiers are engineered to be high-voltage, low current devices; whereas, most of today's modern speakers require high current with relatively low voltages; or exactly the opposite of an OTL design. Ben and his design team believe through their use of four Russian 6C33-B triodes in parallel per channel, a modified Circlotron circuit, a robust power supply, and proper application of negative feedback this goal has been accomplished. The four tubes run in parallel per each channel, adding cathode followers with 10dB of negative feedback. This results in the 003s output impendence being as low as .9 ohms at full power. While this does mean that some of us can run the 003s with dynamic speakers, Navison Audio still recommends a minimum of 8 ohms impedance with efficiency ratings in the high 90s. So in short, unless you are running a very efficient speaker of say 95dB with a minimum of 8 ohms or above you are going to find these amplifiers to be a bit under powered and potentially anemic to some degree at the bottom end. This can be a concern since the majority of today's loudspeakers are in the 4-8 ohm range running and are at around 86-91dB efficiency.
It's all about the sound—isn't it?
Upon receipt of the amplifiers and listening to them for the first time (yeah, I know I should let them break in a while, but damn it they were so pretty I just had to listen to them right away), I was seduced by the stellar detail of the 003s while maintaining the musicality of the upper octaves in my music. It was like these amplifiers had some sort of organic flow to them in that they seemed to be breathing a new life into the music. Never before have I heard an amplifier do this to my music. I was in audiophile heaven. Food for thought …doesn't it seem that quite often, once you have a new piece of gear in your rig, what you hear gets you so excited that you can't wait to call all of your audio buddies to share your new find? This was my experience with the 003s when I listened to them for the first hours they were in my sound room.
Okay so my first impression of the 003s was a great one, but knowing that gear sounds different (usually for the better) over time as it breaks in I knew I had to leave the sound room for a bit and allow the 003s to run in for at least a couple of hundred hours. Upon returning to my listening chair about a week later, I did hear some improvement as the 003s had broken in and started to take shape respective of their "true" sonic signature. Now it was time to place the 003s though my acid test of demo material of blues, bebop jazz, classic rock (my personal favorite), classical, female vocals, and lastly big band jazz. The Focal Automotive Test-CD I use has been my long time favorite, and to this day I still carry it with me to CES and audio club meetings. I acquired this CD about 10 years ago while visiting my last high-end audio gig where I worked as store manager from 1986-89.
Running the 003s with my Aerials was very enjoyable and quite musically convincing. And yet there were times when the music demanded large dynamic swings it appeared that the Navison amplifiers had run out of gas. Well, at least when compared to my Sonic Frontier Power 3 SE monoblocks. The cause was a result of two factors …well make that possibly three factors. One, my Sonic Frontier amplifiers are much more powerful at 260-watts per channel (compared to the 003s 75-watts per channel). Two, the Sonic Frontier amplifiers have a higher damping factor (they are rated at >50 as compared the 003s damping factor of 12) than the Navisons. Higher damping factor usually translates to greater cone control; thus, one experiences quicker and tighter speaker response. Three, the Sonic Frontiers have an output transformer which helps to better match their output to the demands of low impedance speakers - like my Aerials that are nominally rated 6 ohms. Knowing the 003 lacks an output transformer due to its OTL design means that the 003 is more sensitive to impedance issues. Please don't get me wrong, I liked the 003s a lot, but it must be made clear here they didn't really work with my Aerial Acoustics 7B loudspeakers. In short these speakers were not a good match for the NVS-003G monoblocks. However, I believe mated with the right speakers, the Navison NVS-033Gs can provide a sonic purity that is truly overwhelming and awe inspiring; a sonic purity that can transport your spirit to the exact moment in time and space of the original recording. They are that good! But more on that later.
While listening to the 003s I played three different tracks from my Focal test CD as my final evaluation. Again the reason why I use this CD and these particular tracks is because I am so intimately aware of the music with all of its nuances.
First up track one, Junior Wells "Sweet Sixteen" from Everybody's Gettin' Some (Telarc CD-83360). This track has a nice balance to it, in that the sound radiates almost equally front to back and side to side, with excellent stereo imaging. Systems that don't get this track right will end up sounding disjointed. For example the cymbals will appear as if they are coming out of two discrete speakers, as opposed to taking their rightful place center backstage. When listening to the 003s they did not disappoint; all the instruments and musicians were in their proper soundstage location. The music had a nice holographic, almost creamy, presentation that was easy on the ears and a joy to listen to.
Next up was track 2 featuring Michael Ruff's "Wishing Well" from Speaking in Melodies (Sheffield Lab CD-35). I use this track because of the demands placed on an amplifier to get the dynamic swings right. It also features a four person chorus that, if reproduced correctly, one can hear all four distinct voices on the same plane within the soundstage. Many amplifiers, when reproducing this soundstage, will blend all of the voices into one harmonic chorus, but it is not an accurate reproduction of the original. Again, the 003 did not disappoint as it reproduced the soundstage perfectly with excellent layering of performers and instruments. During the piano solo, which I love so dearly due to its big sound and realistic presentation, the 003s did everything right. Even my little acid test of the chorus within the song, all the voices were there along with the hardest of all to hear, the female vocalist. There she was with all of her glory stage left.
Next up was track 10, Jeannie Bryson "Fever" from Some Cats Know (Telarc CD-8391). I use this track for its outstanding close mic'd sound reproduction. The vocalist is accompanied by a drummer, a trumpet with a mute, and a bassist whose performance is so good it almost steals the show from Jeannie herself. Listening through the 003s Jeannie sounded great with her sassy voice being spot on while she performed an old signature song made famous by Peggy Lee. Though the 003s got the rhythm and pace of the song correctly, one thing that struck me was how the 003s petered out of breath when reproducing the demanding bass riff. No the amplifiers weren't clipping; they just were not keeping up with the power demands needed to get the bass right. Thinking this was a fluke I tried other similar material with the 003s, but the results were the same. When the 003s are presented with music that is demanding of an amplifier to take hold of the speakers and command them to do what they needed to do, the 003s just were not up to the task. Knowing upon first glance, or should I say listen, my bubble had now burst. I was at a loss. On one hand I loved the 003s for their excellent soundstaging, immediacy, and an outstanding layering of the organic textures found in my music. Yet on the other hand they clearly lacked bass control and slam, two qualities that I require and cherish from my system. I just couldn't get the 003s to come alive and knock me dead like I have heard with more conventional amplifiers.
Can someone say ...Road trip!
So it has got to be my speakers. Maybe they were not the right match for the 003s? Bearing in mind I don't have several pairs of speakers waiting in the wings (I do have to stay married you know), I decided to take the 003s on the road to my great friend Fred Kat of Katli Audio. On a Saturday afternoon Fred closed his store and me, Fred, and a friend of mine, listened to the 003s for three hours using three different pairs of speakers, and two different preamps (one being Navison Audio's own SEMKII). Again the results were the same as described above, great holographic sound, and creamy and lush transients. However the bass line still lacked that special slam that really makes the aural picture come alive. At this point I was thinking about passing on the review and moving on to another product. But, it was that initial impression that still stuck in my head; along with great holographic imaging, lush but vivid high-end reproduction and a mid range that was so real you swear the performers were there. Those experiences keep me in the review. I had to finish it.
Just about that time Matthew Santa Maria had come on board with Navison Audio as US Marketing director. After having a long conversation with Matt he convinced me to drive to Phoenix, Arizona (350 miles one way) to have a second listen to the NVS-003Gs in his system which he believed was a better match for the 003s. Realizing I had spent over 75 hours of my time researching and writing the preliminary review, and not wanting to toss out my efforts along with the over 40 or so pages of technical text I have read while investigating my research into OTL designs, I decided what the hell, let's go for it! So, once again I am on the road, but this time instead of driving 100 miles round trip I would be driving across state where my round trip would end up being over 700 miles of driving! The things we do for the love of our hobby, or was it the promise of great food once I arrived in Phoenix? Maybe it was a little of both, for those who know me my love for food is equal to my love for our hobby.
After a great dinner at Phoenix's premiere steakhouse, Durant's (where Matthew and I shared a huge 48oz Porterhouse Steak with two 8oz Australian lobster tails, some great wine, and cocktails), we were ready to head over to his showroom and do some serious listening. One quick comment about Durant's, if you are not familiar with the restaurant it is one of the best I have ever experienced. When you think of the restaurant, think of The Sopranos where you enter from the back through the kitchen to the seating area. All of the seats are in red leather—very classic 60s look.
After a settling down (after all I had just eaten half a cow!), we were ready to do some serious listening. The speakers we used for our demonstration were the Bastanis Apollos which, according to Matt, are a high impedance speaker (around 16 ohm) with 98dB efficiency—all of which should be a great match for the NVS-003Gs. Matt was right, these were a great match for the 003s. The life these speakers brought to the table was unbelievable! Everything with these speakers improved, including soundstaging with greater depth both top to bottom, front to back, and wrapping around the speakers. Imaging was holographic and crystal clear, even micro and macro dynamics improved. However, on some tracks I found that I wanted more bass reproduction and a bit more slam, so I informed Matt that this was the same problem I had with the amplifiers at home. Matt suggested this could be due to the subwoofer being turned down, so an easy remedy was at hand. It turns out that the Apollo speakers were not the full range speakers as I had thought. Matt did not mislead me; it was I who didn't ask the right questions regarding his speakers before driving out for our little demonstration. Regrets—none, I did enjoy our time together.
Matt's system did really sound great, though I still would have liked a little deeper (make that more) bass. On one track in particular the 003s really did shine while playing my current favorite CD John Prine Fair and Square (Oh Boy Records OBR-034). I became a fan of John Prine last summer while watching a live PBS performance of his from Austin, Texas. I have to come clean; I am usually not one that steps up to the country music bar. However, I liked John Prine's performance so much (no doubt due to his great story telling) that I bought almost all of his CDs and attended a live concert at the Cerritos Performing Arts Center in Cerritos, California last October! For those of you who have attended a concert at the Performing Arts Center it is an audiophile's dream. When designing the theater, the room acoustics were definitely taken into account as there is not a bad seat in the house. Back to the song of "Some Humans Aren't Humans", the presentation was so realistic that at one point I believed we had arrived at that "absolute sound" we all strive to achieve in musical reproduction. One that is so close the original performance that you feel nothing is missing. I believed this to be especially true after having attended the live John Prine concert shortly after my visit at Matt's home. I do have to say my recollection of what I heard in Matt's sound room was about as close as it gets to the real deal, though one still has to bear in mind the track "Some Humans Aren't Human" is mostly acoustic, it is no wonder the 003s sounded great. However, once the music required bass slam I felt the 003s were a bit lacking. Even with that exception it still was an excellent demo and the drive was definitely worth the time.
So, where am I regarding the NVS-003G? After all I have flip-flopped more than President George Bush Sr.'s comments regarding "no new taxes." For the record I did like my time with these amplifiers though they did not offer the type of bass reproduction that I am accustomed to hearing in my house. As mentioned above this could be due to not having the right speakers that match the 003s so that they could truly sing. For me this goal was never accomplished, even after two road trips and several pairs of speakers auditioned. Perhaps a full-range speaker by Coincident or Triangle Speakers (both rather benign loads) which according to Matt have produced great results with the 003s, would be the right fit. It is with these thoughts that I do still recommend the NVS-003Gs, but with the caution that proper speaker matching is paramount in order to truly take advantage of the 003's OTL design—something that I am sure any Navision Audio dealer would be more than willing to accommodate. Jeff Parks
NVS-003G OTL amplifiers