April 15, 2008
Belles LA-01 Preamplifier and MB-01 Mono Amplifiers
I have many pleasant memories of Pittsford, New York. During the years I was a graduate student at the University of Rochester, I often bicycled down the towpath of the Erie Canal, which runs through Pittsford, ate at the trendy restaurants, and bought fresh fruit, vegetables, and pumpkins at the farm stands just outside of town.
Unfortunately, those memories of Pittsford do not include visiting Dave Belles at his shop, where hes been building amps and preamps for over 30 years. At the time, my audiophile passions were yet to arise in earnest -- I was listening to mid-fi gear and reading absolutely nothing in the audiophile literature. But while Dave Belles didnt found his company, Power Modules, Inc., until a few years after I left Pittsford, he was already deep into applying his engineering skills to the problems of audio amplification, often as a consultant for other companies, and building a body of experience and knowledge that would result in some remarkable audiophile products.
Cases in point: For the last month or so, two of his latest pieces of gear have been doing an amazing job of reproducing music in my listening room. His class-A monoblocks, the Belles MB-01 ($14,000 USD per pair), have been dynamically pumping out music fed to them by his high-end preamp, the Belles LA-01 ($6750). Plus, they look sharp. My wife has a thing about the often strange assortment of gear on the audio racks in my listening room (i.e., her living room), but she liked the silver Belles components and their handsomely coordinated faceplates.
The Belles MB-01 monoblock amplifier puts out 75W biased into class-A, which means it runs hot -- I mean, really hot. A class-A amp is always drawing current from its power supply, and most are designed to deliver far less than 75W -- I was grateful to be reviewing the MB-01 during one of the coldest Wisconsin winters in quite a while. The massive and elegant 1"-thick aluminum front plate is matched with 0.25"-thick panels enclosing the rest of the chassis as well as substantial aluminum heatsinks, for a total weight of 75 pounds per amp. All of it gets warm, and when its been given a workout by playing loudly for a while, the top panel and heatsinks become uncomfortable to touch.
All of this is a good thing. Class-A amplifiers avoid a variety of output distortions associated with other designs, and are generally regarded as having the greatest potential to produce clean, pure, detailed sound. Realizing that potential is another thing, however -- since the Belles A, his first amp design of over 30 years ago and also class-A, Dave Belles has come a long way.
"I havent been building class-A amps, mainly because they cost extra," said Belles. "Theres also the heat problem. But there are definite advantages to pure analog. There are holes in all the competing designs -- class-B, class-AB, and particularly digital switching amps. The signal is chopped up and data is missing. I built the MB-01 for the person who wants to go a little further."
I asked Belles why he went for a solid-state design when the state of the art of class-A amplification seems to be tubes. "There are a number of advantages to transistors," he said. "Reliability is one, plus better bass. You can also get better, more true highs, because you can minimize phase shift better. Tube amps, even the good ones, also tend to sound more colored."
Belles MB-01 is powered by 1000VA toroidal power transformers, and 20 MOSFET power-output transistors slam out the current. The result is that the Belles MB-01 is stable even into a hard-to-drive 1-ohm load, which can be the recipient of up to 458W of peak power.
The MB-01s other components are also distinctly high-end. Metal-film resistors, proprietary polypropylene capacitors, a glass-epoxy circuit board, and OFC wiring are used throughout. Considerable emphasis has been placed on ensuring the synergy of these components, and not merely relying on their reputations for producing good sound. To minimize the chance of those components going fsssst!, theres also a soft-start power-on circuit to eliminate surge transients.
The result is a combination of power and finesse. The MB-01s peak current capability is reported to be a total of 80 amps, while its total harmonic distortion is rated at 0.01%. The frequency response is from 0.2Hz (not a misprint) to 100kHz, and the signal/noise ratio is rated at greater than 100dB. A damping factor of over 5000 keeps an iron grip on the speaker drivers.
Each MB-01 has one balanced XLR and one unbalanced RCA input; the power input is a standard 15-amp IEC socket. The width (17") and depth (13.5") of this hunky amp are fairly conventional, but its tall at 10.5". If you put your amps on a rack, the vertical space between the shelves will be a consideration, particularly with all the heat to dissipate. The MB-01 also comes equipped with Stillpoint feet, which drain internal vibrations away and isolate the amps from external vibration.
I was fortunate to receive one of the first production models of the MB-01s most recent upgrade. The MB-01 is a relatively new design, but when Dave Belles compared it with his most recent monoblock, the Belles MB-200 ($6750/pair), he decided to rework the MB-01 to take advantage of some of the sonic improvements resulting from the MB-200s design.
Bruce Jacobs, marketing director for Power Modules, told me the story: "When we realized that the MB-200 outperformed the flagship, we couldnt let that continue," he said. "Dave took the MB-01 back into the shop and eliminated an amplification stage. He also made the first of the two remaining amplification stages more dynamic. The result was more openness and clarity, as well as a quicker response. Compared with the MB-200, the MB-01 now expresses more midrange beauty and harmonic structure, and is more highly resolving at lower levels."
Belles amps have a reputation for big bass, and I asked how that is achieved. "First, we dont put anything in the way," said Jacobs. "Particularly circuitry that will compromise the timing. One of the goals overall is to shorten the processing time so that we can get the maximum amount of current into the system in the shortest time with the signal intact. Dave is a genius at doing that."
The other component in the Belles trio was the LA-01 stereo line preamplifier, which is designed to provide the signal with a direct and uncluttered path: no tape outputs, no home-theater outputs or circuits, and a focus on listening in only two channels. As with the MB-01, the LA-01s aluminum panels are thick (from 1/4" to 1/2") to eliminate vibrations. Both the preamp and its power supply sit on Stillpoint feet to further isolate them from vibration and improve performance.
The power supply is housed in a separate box and isolated from both the preamp and the AC power source. Connecting the two boxes with a specially designed power cable keeps the noisy power supply from affecting the signal. Four stages of decoupling from the outside AC power line are intended to give the LA-01 a level of performance approaching that of battery-powered preamps.
The LA-01 has four single-ended inputs and two single-ended outputs. The lack of balanced inputs and outputs made me question whether the LA-01 was the ideal companion to the MB-01 monoblock, which has a balanced-input option. Dave Belles said that he has developed and seen the value of balanced designs in situations where many circuits are connected (for instance, when he was involved in wiring the literally thousands of communications circuits at the Cape Kennedy control center in the 1960s), and also when power amps are bridged. But he sees little advantage to balanced circuits in home audio as long as other key elements, such as the ground, are designed well and theres enough output power. "You just end up paying for extra things you dont need," he told me.
Bruce Jacobs raised the potential advantage of a balanced design in driving long or high-impedance cables, or an amp with high input impedance. "But this isnt a problem for the LA-01," he said. "The preamp is producing 10W of class-A, which, even unbalanced, can drive any amplifier and accommodate any cable." Belles himself was straightforward about the benefits of his preamp, which uses power MOSFETs in the output stage: "The LA-01 can give any power amp a good swift kick in the ass."
Beyond power, the LA-01 is designed to provide high-quality amplification without coloring the sound. Belless goal is that it produce detailed sound with clarity and openness, and he expects it to be able to compete on quality and performance with any preamp on the market.
Setup and system
There were a couple of challenges in making sure the review gear was heard in the same context as my reference equipment. The Belles monoblocks and preamp fit nicely on the 24" x 20" x 1" acrylic shelves of my twin homemade audio racks. But all four of the Belles boxes were fitted with Stillpoint feet, which sounded considerably better than the hard rubber feet under my Conrad-Johnson Premier 350 power amp.
So for the first week or so of listening, I used my own vibration-control devices (myrtlewood blocks sandwiched between slices of hard agate) under everything, lifting the Belles Stillpoint feet into the air so they no longer functioned. A much better-sounding solution presented itself shortly afterward, when I was able to borrow some Stillpoints with risers to use with the C-J for the duration of the review. They uncluttered and clarified the sound beyond what my own improvisations were capable of, without changing the pitch of the instrumental timbres. Dave Belles was wise to include Stillpoints as standard equipment with these products. I liked their effects so much that I bought a batch of them after finishing my listening for this review.
The other challenge had to do with the power supply. First, I plugged all the gear into my PS Audio Power Plant Premier power regenerator, but after a few minutes of listening discovered that the sound was starting to break up. PS Audio warns that there may be brief occasions (usually transient events such as powering up a big amplifier) during which the Premier cant regenerate enough current for the devices connected to it. But the Belles monoblocks, hungry for current all the time, may have overloaded the power regenerator. That was fixed by hooking up the MB-01s to a Shunyata Research Hydra Model-4 power conditioner and leaving the Power Plant Premier to handle the source and preamp. Although my C-J amp works well with the PS Audio Premier, for the purposes of comparison, I also used the Shunyata Hydra with my reference amp during testing.
Other gear on board for the review included an Esoteric X-03SE SACD/CD player, a Bent Audio NOH passive-transformer line stage, Triangle Stratos Australe and Esoteric MG-20 loudspeakers, Legenburg Apollo speaker cables and Hermes interconnects, and ESP Essence Reference power cables.
To get a sense of how the Belles products worked together and by themselves, I listened to various combinations of my reference gear and the LA-01 and MB-01. My first impression of the Belles combo was a simple one: "Wow, this is fun!" Any music that had a bit of swing or drive to it -- such as "Cantaloop (Flip Fantasia)," from Hand on the Torch by Us3 [CD, Blue Note 102362], or "Bean Time," from my favorite live album, Leo Kottke Live [CD, On The Spot 2132] -- got the chance to show off its paces. If one of your criteria for enjoying music is to feel foot-tappingly engaged, the Belles gear needs to be on your audition list.
At the same time, the Belles combo did a great job of preserving the timbral accuracy of acoustic recordings. For instance, I found myself listening a number of times to a CD of piano jazz, New World A Comin [CD, Centaur CRC 2468]. Composed by my friend Joe Makholm (plus a couple of guys named Brubeck and Ellington) and played by Willis Delony, this isnt the most sonically sophisticated solo-piano recording. But the combination of very engaging music, a credible performance by Delony, and the Belles gears ability to reveal the drive and drama of the music, made it something I repeatedly returned to. What made it particularly appealing was the same thing that Sherlock Holmes found remarkable about the dog in the night: the piano never "barked," never sounded like anything but (remarkably) a piano.
I found the same virtues displayed in larger orchestral pieces, such as Chabriers Espana, performed by Paul Paray and the Detroit Symphony [SACD, Mercury Living Presence 475 6183]. This high-resolution reissue is an orchestral workout with dynamic range and drama, and the Belles gear brought forth its best. It was easy to listen deep into the recording for details, and the orchestra filled the soundstage with convincing images.
In rearranging my equipment so that I could compare the MB-01 more directly to the C-J Premier 350, I found that the MB-01 had impressive microdynamics and dug a bit deeper than the Premier 350 into the subtly expressive elements of the music that make it sound more realistic and present. The C-J was a bit leaner and perhaps more detailed, the Belles richer and more expressive. Both let acoustic instruments speak in their natural voices, but the Belles went deeper and more expressively into the lower frequencies. Overall, the Premier 350 sounded a bit tighter and more in control, the Belles MB-01s bigger and more enthusiastic.
The comparison of the LA-01 with the passive-transformer Bent Audio NOH was interesting in part because it perhaps illustrated the strengths of the differing technologies as much as the differences between the two preamps. With the LA-01, the edges of the music were a bit crisper than with the NOH, and all types of percussion, including piano, sounded more impactful. The Belles preamp was captivating and dynamic; it would not let me ignore the music. Another orchestral piece illustrated this beautifully: Aaron Coplands "Hoe Down" from Rodeo (better known as the music in the "Beef -- its whats for dinner" ad campaign), performed by Robert Shaw and the Atlanta Symphony [SACD, Telarc SACD-60648]. The dynamic shifts in this recording were more expressive through the LA-01, an effect that held true for any number of jazz and pop tunes I played through this preamp over the course of the month.
On the other hand, the LA-01 has electronic components in its signal path, and, being a pair of passive transformers (curved wires with gain?), the NOH does not. Instrumental timbres were more natural through the Bent, with an inner smoothness and reality to the texture of acoustic sounds. The Belles preamp made violin and orchestral details slightly more edgy and less convincing in Coplands Appalachian Spring (also from the Telarc SACD), and it was a bit harder overall to be drawn into classical and instrumental music on an introspective level.
Considerations and conclusion
To thrive, the Belles MB-01 monoblocks need the right sort of environment: unobstructed electrical current, plenty of space to dissipate the heat they generate, speakers that work well with high damping, and an owner with $14,000 to spend. Assuming those conditions are met, the MB-01s offer an enormously appealing way to listen to music. Theyre detailed, dramatic, and downright seductive in their expressiveness. As Dave Belles said, they are for "the person who wants to go a little further" into the territory where sound quality is not compromised by the design restrictions of amplifiers not biased into class-A.
The LA-01 preamplifier is a great companion for the MB-01. It matches the MB-01s expressiveness and enthusiasm, and easily draws one into the music. While it may lack the last bit of refinement, it more than makes up for that with its appetite for drama and flair. Anyone who listens to music with bounce will find this preamp appealing. Its high output also makes it more likely to work well with other amplifiers, and it has the power to drive signals a long way down a single-ended interconnect, if it has to.
No longer will I suffer a lack of pleasant memories related to Dave Belles. Ill remember the MB-01 and LA-01 as some of the best amplification gear Ive ever heard.
MB-01 Mono Amplifiers
Power Modules, Inc.
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