July 2011

World Premiere!
Napa Acoustic Mistral MT-34 Integrated Tube Stereo Amplifier
A wonderful unit that the wife will love!
Review By Alfred Roy Fredel

  Over the years, I have seen audio gear manufacturers come and go and it is a great thing to see new blood infused into our industry. The consumer is now very well conditioned to get the most they can for their hard earned dollar, more so now in this difficult economy. As many of you know, getting the best value/performance ratio is always on my radar and I enjoy sharing my thoughts about gear that fits this profile. Enter Napa Acoustic, a company that also shares these same values by bringing high quality products to market that are affordable for all music lovers.

Napa Acoustic was formed in August of 2009 as a design and production company focused on building and selling acoustic room treatments and audio equipment. Also in 2009, Napa Acoustic chose to represent Mistral Audio in the United States, an audio manufacturer from China. Mistral Audio has more than 10 years of experience in designing and producing high quality audio products and they have collaborated with Napa Acoustic to design several of the offerings that they represent here in America. The company is recognized worldwide, earning high marks for their equipment and loudspeakers and have now started targeting the United States marketplace. By offering innovative audio products at affordable prices, Napa Acoustic and Mistral Audio hope to make a successful entry into this tough and crowded market.

Napa Acoustic offers several vacuum tube based integrated amplifiers that are all under $2000. For as little as $399, you can have the warmth of "tube sound" in your home or office. This is exactly the target audience that I enjoy engaging: people looking for good sound at a reasonable price. After speaking with the company's president Joseph Kwong, I decided to review a new piece that is being readied for release to the American market that is a lot different from Napa Acoustic's current offerings. This new product, Mistral's MT-34 integrated amplifier, is a little bit upstream in terms of price point from their current inventory but even at $1199, it is more than fairly priced in regards to its competitors.

The Mistral MT-34 is a 35 watt per channel stereo integrated amplifier that features two heavy-duty toroidal power transformer, solid-state rectifiers and oversized Raytheon capacitors for high voltage. One of the toroidal transformers is dedicated for high voltage (335V), while the other transformer is for filament voltage and negative bias voltage. The preamplifier section of the unit consists of one 6n1 vacuum tube for each channel set in a shunt regulated push-pull configuration. The power amplifier section of the unit features one 6n1 and two EL-34 tubes in shunt regulated push-pull arrangement for each channel. Fixed biasing is incorporated for each EL-34 vacuum tube. The compliment of tubes for the power amplifier section are Chinese Shuguang branded valves, which have been noted to be good performers by many tube enthusiasts and are based on a classic German design that is known for its low mechanical noise. Around back, the unit features well-made binding posts with taps for 4ohm and 8 ohm loads, two high quality sets of RCA inputs with a toggle switch to select each input and a detachable power cord and power switch. Looking at the front, there is simply a rather large yet elegant volume control directly in the center of the panel. The look is clean and sophisticated with a solidly built chassis that is double layered in a high gloss black finish. The unit is sturdy and really pleasant on the eyes with a demure footprint for such a hefty piece. Also included is a cage that nicely protects the tubes and little fingers, but lets the beauty of the tube glow shine through, something that every tube lover covets.

Finding The Right Space
There is a lot of audio gear in my humble home and finding a spot for this new piece was not an easy task. The challenge was to find a space that was not too small with adequate room to let the MT-34 perform. I found a space in our dining room much to my wife's displeasure. There was an empty space on the dining room furniture and that is where it settled for the duration. Eventually, the MT-34 became a very conspicuous centerpiece in that room. Along for the ride, I enlisted a pair of Arcaydis bookshelf monitors at 4 Ohms and a pair of Rogers LS8a floorstanding loudspeakers at 8 ohms. Interconnect cables are from XLO and speaker cables are Audioquest Rocket 33 at 8 feet. The front end for this listening experience included a PURE i20 iPod dock with digital out, a Musical Fidelity V-Dac and an Audio Refinement CD Complete. The dining room is 15 feet wide and 20 feet deep, enough room for the MT-34 to sing to me.

I first connected the Arcaydis bookshelf monitors, since it was easier to place them in the room. My initial thoughts were very positive about the sound that I was hearing through the PURE i20 dock and Musical Fidelity V-Dac digital to analog converter. The high-resolution files on my iPod sounded rich with detail. I noticed that there was a very nice tonal balance between the instruments, especially on my favorite jazz recordings. In "Waltz for Debby" by Bill Evans, the piano and bass were clean and the imaging was strong. The unit presented a very believable soundstage. The MT-34 excelled when it came to vocal, acoustic or instrumental music. In most recordings the bass was clean, although it could have used a little bit more impact. As the music began to become denser, I sensed that the MT-34 might not be comfortable driving the 4ohm load due to some slight distortion that I began to hear. There was no punch when I fed the unit some of my "chunkier" rock and pop files. It was interesting to note that the same effect occurred while listening to various CDs on my Audio Refinement CD Complete. I decided to ditch the 4ohm monitors and connected the Rogers LS8a loudspeakers that were a lighter load at 8ohm and a little more sensitive. This proved to be a good choice and made a world of difference.

With an 8ohm load, The MT-34 seemed to be in its own element. Gone was the strained sound that I heard at times with the 4ohm monitors. With the new loudspeakers, the bass tightened up and was punchy and the sound became more involving and smooth. I would definitely recommend that one consider an efficient loudspeaker with a lighter load to pair with this integrated amplifier.

The Joy Of Tubes
For many, the experimentation process and customization is part of the joy of choosing to own a tube amplifier. Unlike solid-state equipment, the user can easily swap out the vacuum tubes they have to the offerings of another manufacturer or in some cases a different tube all together to suit their taste. Napa Acoustic has suggested that one can use an EL-34 or 6CA7 for the power amplifier and 6N1 or ECC40 marked tube for the preamplifier. I believe that the Chinese EL-34 tubes provided with the unit sounded very good, but I wanted to try a matched quad set of Russian-made Electro-Harmonix EL34EH tubes. I find them to be extremely musical, with a sound that is rich, smooth, and highly detailed without being harsh. To my ears it made a big difference in the sound of the MT-34. There was more detail and better bass response when using the EL34EH tubes. This was very clear to my ears on Nelly Furtado's track "Say It Right" from her album Loose. On this track, there is a lot of percussion that dominates the song and the MT-34 with the Electro-Harmonix tubes handled it with ease. All throughout, there was a warmth and presence that was truly wonderful. Had I had a bigger selection of tubes on hand, I could have spent weeks lost comparing the pros and cons of each of them.

Summing It All Up
Okay, tube amplifiers are not for everyone. There is always the chance that a tube will die, the amplifier is not properly biased and the maintenance needed to keep up the unit is more that the user bargained for, but the rewards can many times outweigh these minor inconveniences. With tubes, you get warmth, detail and the flexibility to experiment with different combinations that can make a real difference. The MT-34 is a solid choice in which to enter into the world of tube amplification and again with the price tag of $1199 it is a considerable bargain. Considering its sturdy build, use of quality components, aesthetic appeal and sonic performance, there is very little to say other than it is just a wonderful unit. After a while, my wife got used to having the MT-34 as the centerpiece of our dining room and commented that it actually looked and sounded nice. Score one for Napa Acoustic and Mistral on the wife approval scorecard and one on mine for very good sound.

Specifications
Type: Stereo integrated tube amplifier 
Frequency Response: 20 Hz to 25 kHz
Tube Compliment: One 6N1 and four EL34
Power Output: 35 wpc, two channels 
Output impedance: 4 or 8 Ohms
Inputs: AUX and CD
THD: <1% at 1kHz
Signal To Noise Ratio: >90dB
Input Sensitivity: 300 mV 
Input Impedance: 100 kOhms
Size: 300 x 460 x 200 (WxDxH in mm)
Weight: 33 lbs.
Price: $1199

Company Information
Napa Acoustic
44380 S. Grimmer Blvd
Fremont, CA 94538

Voice: 510-371-3416
E-mail: info@napaacoustic.com
Website: www.napaacoustic.com