POSITIVE FEEDBACK ONLINE - ISSUE 30
i84 integrated amplifier
as reviewed by Akhilesh Bajaj
Vista Audio is a relatively new manufacturer. I had many conversations with Boris Sasic, the head of their engineering section, in the course of writing this review, and Boris emphasized to me that Vista relies on objective engineering measurements first and subjective impressions, or "voicing," second. Given my penchant for single-ended triode (SET) amplifiers—products that usually do not measure well but have an ineffable musicality and rightness—you would be correct in categorizing me as someone who puts sonic impressions first and measurements second. But then, I am in audio primarily as a hobbyist, and can afford to indulge in my pet beliefs. A manufacturer is answerable to a wider audience, and objective measurements are much more defensible than subjective qualities.
This being said, I prefer to discuss how Vista's 15-watt-per-channel i84 integrated amplifier sounds, as opposed to how it measures, so I'll get the measurements out of the way quickly. According to Vista, the i84 has very low total harmonic distortion (THD), below 0.5 percent, and a relatively linear increase in THD with increase in power. I have no reason to doubt Vista's claims, especially since they do not seem outlandish. The i84 is a push/pull amplifier of classic design, using two EL84 output tubes per channel, with the ubiquitous 12AX7s used as input/driver tubes, one per channel. The amp retails for $729. The run from which my sample was sent had a small manufacturing error—the input connectors for the left channel had red connectors, which is contrary to industry practice. According to Boris, there was a mixup in the assembly drawings. To compensate for the error and reinforce their commitment to quality, Vista decided to offer the units from this batch at a 15 percent discount, for a total of $619. Quoting Boris, "The quality of our product has always been well above their price, and it has to stay that way." Vista offers a fourteen-day, money-back guarantee, not including shipping, and a tiered restocking fee for sixty days. The amplifier also comes with a two-year warranty.
My conversations with Vista, as well as my impressions of the i84, indicate that care was taken in the construction, especially where it affects the sound. The amp has a nice, clean appearance. The chassis has a mirror finish, with plastic side panels in piano black. Like many Far Eastern offerings, the amp comes with white cotton gloves to maintain the mirror finish. It is not going to win any design awards, and it certainly does not look expensive, but I think it looks a lot better than the DIY kit amps available in its price range. I prefer the subtle look of the i84 to that of the more lurid offerings of today, and suspect that it will pass the test of spouse acceptance. If you are looking for lots of wood and chrome (or worse, gold), this is not your amplifier, but if internal parts—ones that are actually in the circuit—are important, the i84 delivers.
I am a big believer in good parts, especially output transformers, power supplies, and coupling capacitors. While output transformer quality is more critical in SET amplifiers, it is also very important in push/pull designs. Unlike many inexpensive amplifiers available today, Vista claims that the i84's transformers are made from "transformer grade" metal, not scrap metal. Further, all of the i84's transformers are completely potted in thermally conductive epoxy to eliminate any possibility of mechanical hum and to facilitate heat transfer. The benefits are: (1) slower aging, and (2) a smaller increase in winding resistance. The amp is assembled in Serbia, and uses toroidal transformers supplied by the Trafomatic Company, located in that country (for information, go to www.trafomatic.com). According to Boris, the core material is grain-oriented steel M5 or M6, 0.27mm thick, and the sourcing varies between Sweden, Bulgaria, and South Korea. Transformer insulation, a critical element, is sourced in Germany. The power transformer is oversized by 25 percent, and the output transformers are oversized by 33 percent.
The power supply is a capacitor-resistor-capacitor type, and uses bypassed solid-state rectifiers. The coupling capacitors are metallized polypropylene film, with construction equivalent to WIMA MKP10. The volume control is made by ALPHA, with an equivalent ALPS as a second source. An upgraded power cord (Shield III by Audio Limits of Canada) is available for an additional $60, but I listened to the amplifier with the standard 14-gauge power cord.
The i84 arrived in a compact box, about 12 by 8 by 16 inches, and weighed about 17 pounds (yes, I weighed it). It was double-boxed, and packed with lots of Styrofoam and peanuts. A simple, to-the-point manual was included, once again emphasizing that Vista is low on marketing and high on engineering. According to the manual, the EL84 output tubes should be replaced every 1500 hours (about 18 months), and the 12AX7 tubes every 2500 hours (about two years). At current prices, it will cost about $50 to retube this amp.
The i84 was very easy to set up. It has nice, thick, high-quality speaker binding posts that can easily hold 8-gauge speaker wire. The power switch is at the back. The amp felt very light to me, but this was probably because the output transformers in a push/pull amplifier are lighter than those in a SET amp.
On to the listening. I let the i84 play for about forty hours before listening to it, which burned in the circuitry and the tubes somewhat. After starting to listen, my impression was that the sound of the amplifier did not change significantly after the initial burn-in, although a warm-up time of about five minutes was useful for best results. I used two different systems to get a handle on the i84. In the first system, I used a pair of single-driver speakers that employ a D'Charles Audio 5.5-inch full-range driver in a PAWO horn. While these speakers are somewhat unconventional (to the best of my knowledge, only two pairs exist), they are the only speakers I've heard that offer reasonably high efficiency (around 90dB), that allow me to listen to a full-range driver with no passive or active electronics, AND that reproduce frequency extremes satisfactorily, have reasonable dynamic range, and have no irritating frequency aberrations. In other words, these speakers offer as much purity as I know how to get, while keeping things realistically musical.
Lest you think I'm a single-driver fanatic, I should say that of all the speakers I currently listen to on a regular basis this is the only one that is pure single-driver. It is also not my primary speaker system. However, if the goal is to evaluate a component in the upstream signal path, it is best to minimize speaker-related problems, and this setup certainly does that. For the source, I used a modified, non-oversampling TDA154A-chip Philips CD player, a source used by ultra-fanatical analog purists who want the coherence and realism of analog sources, especially in the highs. The speaker cable was 10-gauge wire bought from a large electronics store, hand-trimmed, without terminators, by yours truly to the minimum required length, about five feet. I used simple Radio Shack™ gold-plated interconnects, one meter in length—again as short as required. I did not use any power filtration, since the goal was to get a feel for the broad sonic qualities of this amplifier rather than focus on the small improvements gained by tweaking.
The room in which this system was set up was a living room, about 12 by 16 feet, with a ceiling that slopes up in the middle from about 9 to 14 feet. The room has about average liveness or reverberance. At first, I used a Far Eastern 2A3 SET amplifier (3-4 watts) that I own and have tweaked with better tubes, and that costs about the same as the i84. The system sounded musical and clear. In fact, I was impressed with the 2A3 amplifier, since I had rarely run it full range. The sound was something I could live with. When I substituted the i84 for the 2A3 amp, there was a significant improvement in three areas: bass, dynamic range, and transparency. The i84 had much better control of the drivers, so the quality and quantity of the bass was much better. There was also more transparency, and I could hear the highs a lot more clearly. Finally, the system exhibited significantly more dynamic range than it did with the 2A3 amp. The i84 was the best match for the single-driver speakers of all the amplifiers I tried, and it made me appreciate them even more than I had before.
I played many different types of music on this setup, over a period of several weeks—including female vocals (Sinead O'Connor, Diana Krall, and Margaret Timmins of the Cowboy Junkies) and classical music (Holst's The Planets and pieces by Beethoven and Mozart). I also played the Ultimate Demonstration Disc by Chesky Records. This disc has several cuts that are helpful in evaluating an audio system, demonstrating qualities like dynamic range, transparency, focus, and midrange purity. The i84 handled these tracks well. I'd rate it as very good to excellent, with its strong points the ones I have already mentioned: bass, dynamic range, and transparency. Soundstage depth was as good as it was with the 2A3 amp, as were the highs. The "Visceral Impact" track on the Chesky disc had almost no impact with the 2A3 amp, but with the i84, I could feel it. Every instrument sounded clearer and more delineated, and imaging was rock solid. The differences between the tonalities of similar instruments (for example, the "Visceral Impact" track has two drum sets) was easier to discern with the i84.
At one point, a friend brought over a Sophia Baby amplifier, and we compared it to the i84. The difference in power output was obvious, as the Sophia needed to be turned nearly to maximum to get anywhere close to the volume that the i84 achieved at 9 o'clock. The midrange was a tossup, with the Sophia producing a softer, more rounded tone. My friend preferred the midrange of the Sophia, as he considered it more musical. I slightly preferred the clarity of the Vista amp. The i84 had significantly better bass control and extension. We both agreed that the Vista amp was ballsy, reminiscent of the old organ amplifiers. In my opinion, the advantages of the i84 greatly outweighed its weaknesses in comparison to the Baby. At one point in my listening sessions with this system, I tried using a laptop with an average-quality soundcard. The laptop sounded slightly different than the Philips CD player, but the sonic qualities of the i84 were consistent with what I had already observed.
Next, I thought it would be fun and informative to try the i84 in a very different system, with the same CDs. The first source I tried in this system was a Pioneer PDR509, an inexpensive CD recorder with what I would characterize as late-'90s mid-fi sound. The Pioneer was connected with inexpensive three-foot interconnects to a .9-watt 12B4 SET amplifier, which was connected with AudioQuest speaker cables to a pair of 1978 Klipschorns with updated crossovers. These speakers have a clean balance, with the updated capacitors in the crossovers making a very large difference in coherence and clarity. Despite their 104dB sensitivity, the K-horns are a moderately difficult impedance load. My 12B4 amplifier has very clean highs, a pronounced midrange, and somewhat reduced bass. It works well on the K-horns because of their extreme sensitivity. The room was a little smaller than the one I used for the first system, and quite dead acoustically (a good thing). After listening for about an hour to this setup, I replaced the 12B4 amplifier with the i84. Not surprisingly, there was much more bass and dynamics, but the midrange sounded a little compressed and the top end was a little bright.
Then I removed the PDR509 and changed the source to a Berendsen CDP-1, a high-end CD player built in West Germany. The Berendsen transformed the sound quite significantly. It was much more musical, still very detailed, but much better balanced and more rounded, with no brittleness at the top end. The fact that I could perceive these changes testifies to the transparency of the i84, which transmits everything in the signal path. The $600 Vista amp fit in quite well with a $2200 CD player and the expensive Klipschorns. The strong points of the i84 were the ones it had exhibited in the previous system—bass control, dynamics, and transparency—but the differences in dynamics were more emphasized because the 12B4 amplifier is of such low wattage. The "Dynamic Range" track on the Chesky disc revealed the i84 to be much better in this department.
After listening to this system for a while, it began to seem a little crisp to my SET-attuned ears. One of the advantages of the i84 is that you can switch the input tubes from 12AX7/ECC83s to 12AU7/ECC82s. When I removed the stock 12AX7s and replaced them with a pair of NOS ECC82s, I heard subtle but audible changes. The ECC82s made the i84 softer and more rounded, with a slight loss in clarity, all of which makes it sound more SET-like. With these tubes, this system sounded more musical to me. After listening for a few more days, I substituted the 2A3 amplifier that I had used in the first system for the i84. The midrange was now more pronounced, but some of the bass control and dynamics were lost. Still, given the very high efficiency of the K-horns, the losses were smaller than they had been with the single-driver speakers. Even with the NOS input tubes, the i84's midrange was not as smooth and rounded as that of a SET amp, but its dynamic range, clarity, and bass control were much better.
I've said several times that one of the strengths of the i84 is bass control. I do not mean to say that the bottom end is overemphasized, just that there is a lot of well controlled bass. There is no rounding off or softness in the midrange, either—no lush images, just clean, crystal-clear sound. On brighter systems, it may be advisable to use 12AU7/ECC82 input tubes, but on neutral or dark systems, the supplied 12AX7/ECC83s will work just fine.
The Vista i84 will be an excellent fit for systems of moderate to high efficiency that need more bass control or transparency. If you own single-driver loudspeakers, you owe it to yourself to audition this amplifier. If you own ultra-efficient horn speakers, the tradeoffs between a SET amp and this amp will make your choice more difficult, since a good SET will do some things (midrange softness and musicality) that the i84 will not do, while the i84 will be better in other respects (bass control, transparency, and dynamics). In my experience, as the speakers get less efficient, the i84 becomes progressively superior.
Aside from the Sophia Baby, I have only compared the i84 to SET amps, which may lead to cries of "Foul!" but most people who are considering the i84 will also be looking at SET amplifiers in its price range. I do need to add, though, that compared to other push/pull amplifiers that I have heard, the i84 really has no weak points. In my opinion, sound quality is not in the circuit but in how it is executed, and the i84 is one of the best executions of the classic 12AX7/EL84 configuration that I have heard. At its price, the Vista i84 is a steal, especially when compared to some of the similarly-priced kit amplifiers that come with cheap parts. I strongly recommend the i84 amplifier for its value, its quality of manufacture, its capacity for inexpensive tube-rolling, and last but not least, its superior sound. Akhilesh Bajaj