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Equipment Review
October 2001

Belles 350A Stereo Amplifier

by Doug Blackburn

Reviewers' Choice Logo

"Definitely this reviewer's choice."




Review Summary
Sound "A wonderfully transparent, open, unsmeared, pristine, and clean-sounding amp"; "dynamic capabilities…are right up there with the best you can find"; " no character to the 350A's mids," which also applies to the treble; "bass performance came from remarkable driver control, incredibly low distortion, rich detail, pitch-perfect tonality and a combination of brute power and stunning dynamics."
Features MOSFET output devices, bi-polar voltage gain, and J-FET input stage; balanced or RCA connections, detachable power cord; ultra-high damping factor and ultra-low crossover notch distortion were design goals.
Use Will drive almost any loudspeaker load effectively; best when used with other components that are also neutral, transparent, detailed, and natural.
Value "The amp for audiophiles who want super-amp sound on an under-$4000 budget."

The 350A is a typical Belles/Power Modules product. Like the 150A and 150A Hot Rod amps, it is all about the sound. The visual and tactile aspects of the products are perfectly adequate for the job, but nothing fancy. The 350A is presented in basic black. The heavy front panel has two milled vertical detail lines, an LED, and a power switch. The rear panel contains the high-quality binding posts, RCA inputs, XLR inputs, balanced/unbalanced toggle switches, and IEC connector for the power cord. The full-height cooling fins run the length of both sides and are very closely spaced.

The power rating is 250Wpc into 8 ohms and 400Wpc into 4 ohms. The 17"W x 5 1/4"H x 16 1/2"D, 65-pound, dual mono $3495 USD 350A has the circuit boards and output devices mounted directly on the heat sinks to minimize internal wiring. A single 2000kVA transformer is used rather than a pair of 1000kVA transformers to provide more current for bass transients.

The 350A’s unique character is a result of a new amplifier circuit that Dave Belles is reluctant to reveal too many details about lest his work starts to appear, uh, elsewhere. But Belles does reveal that the input stage uses J-FETs, the voltage-gain stage employs bi-polar devices, while the output stage is MOSFET. Each solid-state device is selected for suitability and sound quality in each specific application.

There are three design aspects that Belles will discuss in generalities: crossover notch distortion, class-AB operation, and damping factor. Belles’ new circuit for the 350A is claimed to essentially eliminate crossover notch distortion, including any amplitude or temporal mismatch between the positive and negative halves of the waveform. He believes that this new approach is responsible for the openness, ease, and clarity that the 350A has. Dave Belles has also been a big proponent of class-A amplifier design for many years, but with 350A's circuit, class B was taken to what Belles believes is so close to sonic perfection that it makes class A superfluous. The 350A employs only a few watts of class-A operation to generate enough heat to keep the output devices and other internal components in a temperature range that sounds good. Finally, for the 350A, Belles ended up with a damping factor that is incredibly high -- "over 1000," but just between you and me, it is way over 1000. To put this in perspective, even expensive push-pull tube amplifiers have a difficult time exceeding 20. Single-ended tube amplifiers will generally have damping factors under 10, perhaps way under. The Mark Levinson No.33-series amplifiers, which are considerably more expensive than the 350A, have a damping factor specified as "greater than 800." Belles’ "over 1000" specification indicates that the amplifier essentially absorbs anything that is returned from the loudspeaker with no effect whatsoever on the output of the amplifier.

Clear as a Belles

The 350A is a wonderfully transparent, open, unsmeared, pristine, and clean-sounding amp. The effect of all this clarity is one of no barrier, not even a sheet of sonically transparent Saran Wrap, between you and the musical performance. You can clearly observe this superior transparency on standard CDs like the exceptionally well-produced Steve Davis Project Quality of Silence [DMP CD-522], on which the silent spaces between notes are as much a part of the music as the notes themselves. The 350A produces absolutely clean silences punctuated with pure, dynamic, rich instrumental tones. It reveals the recording as it was recorded without editorial comment. There is no sweetening, no artificial depth added, no huge soundstage injected where none actually exists. But put on a recording that has these characteristics, like the remastered Dire Straits Love Over Gold [Warner 947772-2], and hold on for one massively entertaining listening experience.

The Live Recordings at Red Rose Music sampler [Red Rose Music RRM01] is an excellent test for the subtler aspects of an audio system’s performance. I was impressed by how lively and natural the sound was when my system was driven by the 350A. Piano notes launched into the room like musical fireworks -- all percussive at the beginning, but quickly becoming round, sweet, soft, and mouthwatering with an amazingly delicate and rich decay to silence. And the decay itself was perfect -- harmonically rich, tonally pure and containing an ideal balance of both string and cavity resonance. The 350A consistently produced solid, pure tones with all the complex harmonies and heartbreakingly delicate decays all the way down to the noise floor of the recording. I’ve heard sax played live in my listening room, and I have to tell you that the sampler tracks with sax on them made the hairs on the back of my neck stand up. It was just like having a sax in the room again. The image was so solid that I half expected to be able to reach out and touch the instrument.

Associated Equipment

Loudspeakers – Green Mountain Continuum 2, Vandersteen 3A Signature with two Vandersteen 2Wq subwoofers.

Amplifier – Belles 150A Hot Rod.

Preamplifiers – Audible Illusions Modulus 3A with Gold phono boards, Belles 20A.

Analog – Roksan Xerxes turntable, SME V tonearm rewired with Nordost Moon Glo cable, low-output Cardas Heart cartridge.

Digital – Perpetual Technologies P-1A/P-3A, Assemblage D2D-1, heavily modified Pioneer DV-525 DVD player with Audiocom DVC-1 Master Clock Kit (used as a transport).

Digital cables – Cardas Lightning, Perpetual Technologies I-squared-S cable.

Interconnects – Analysis Plus Copper Oval, Audience Au24, Magnan Signature, Nordost Quattro-Fil, Nirvana SL.

Speaker cables – Analysis Plus Copper 9, Audience Au24, JPS Labs NC Series, Magnan Signature.

Power cords – Analysis Plus Power Oval; Audience Power Chord; AudioPrism SuperNatural 9.5; JPS Labs Analog, Digital, and Power AC.

Power conditioners – VansEvers Model 85, Unlimiter, jr. Video, jr. Analog, Reference Balanced 5; Magnan Signature; two Richard Gray's Power Company 400S; two Quantum Life Symphony.

Room acoustic treatments and accessories – Michael Green Audio and Video Designs Pressure Zone Controllers, Argent RoomLens, VansEvers Spatial Lens and Window system, AudioPrism Wave Guides Nordost Pulsar Points.

The dynamic capabilities of this amp are right up there with the best you can find. The 250Wpc will keep up with any real-world loudspeaker and leave headroom for reproducing even sustained dynamic peaks, all with no sense of limiting or compression. High-energy recordings like Paula Cole’s This Fire [Warner/imago 946424-2] and Erich Kunzel's Big Band Hit Parade [Telarc CD-80177] can stress even some powerful amps driving demanding loudspeakers at moderately loud listening levels. But with the 350A, both of these recordings could sustain louder levels than I cared to endure for any length of time with no hint of running out of steam or compressing even the smallest detail.

When the music gets slower and dreamier, the 350A shifts gears to compliment the suave sounds as if born to the task -- also quite apparent on both of these discs as they contain a mixture of maximum-volume tracks and slower, sweeter sounds. When the amp ratchets down for the quieter work, sounds don’t change character. Piano, for example, has the same wonderful tonal character it has when being played more forcefully; it’s just brought down to scale. The 350A is consistently excellent in presenting dynamic contrasts at every volume level. The entire loud-to-subtle range of sonic details is laid out with amazing precision, allowing you to hear every detail with complete clarity but without any forced or pushy character of any kind.

My first reaction upon hearing how the 350A made the Vandersteen 3A Signature's sealed-enclosure woofers sound was to chuckle. I was finally hearing how good the bottom end of these loudspeakers could be. When the 350A was used with the Green Mountain Continuum 2, which has a ported 12" woofer, the change in bass character was almost astonishing. The woofer suddenly came under the iron-fisted control of the 350A and did things and produced effects that other amps I tried with the speaker just could not duplicate. The 350A literally made the Continuum 2 sound like it was a much more expensive loudspeaker. The deep bass on the Paula Cole This Fire disc was better than any amp that has been in my system --– massively better than most other amps, but not to be mistaken for the over-emphasized bass you may have experienced from some amps. This bass performance came from remarkable driver control, incredibly low distortion, rich detail, pitch-perfect tonality and a combination of brute power and stunning dynamics. The bass of this amp is so obviously outstanding that it still makes me smile during every listening session.

And the deeper the bass, the more advantage the 350A has in terms of bass detail. Drum sounds are widely varied and ultra detailed on Emmylou Harris’ Wrecking Ball [Elektra/Asylum 61854-2]. Skin sounds are revealed to be a composite of three to six different types of sound depending on the drum type. There are some rather powerful deep-bass synthesizer notes on Paula Cole's This Fire. The 350A reproduces them with great solidity -- the sounds take on a physical presence in the room. In comparison, other amps have moved a lot of air, and moved the floor and walls, but none of them convinced me that those sounds were a physical presence, an entity, in the room.

There was no character to the 350A's mids. Every recording sounded different -- but always clean, totally transparent, completely neutral and incredibly detailed. Ease, speed and tonal accuracy are the hallmarks. There is no tendency to darkness or brightness. There are no "a little too much of this" or "not quite enough of that" situations. Every recording I listened to sounded perfect, within the confines of the production and mastering quality, that is. Bad recordings like the too-bright Beatles CDs were still enjoyable in spite of the production flaw. Good recordings were not over-hyped, over-detailed, or exaggerated in any way. I have to admit that I was half expecting the 350A to make less than ideal recordings unpleasant to listen to -- so good was it on great recordings. Whether the perspective was forward or distant was completely a function of the associated equipment and cables. I was able to place the front of the sonic stage at any distance that felt right to me by selecting the right associated components.

The comments I made about the mids apply equally to the treble -- the 350A doesn’t editorialize the highs in any way. The range is fully extended, and you will hear everything the rest of your system reproduces, good or bad. You can’t ask any more of an amp. The highs aren’t sweet, pretty or polite. There is no roll-off, brightness, or harshness. But you can hear all of those things if they are present in the original recording. If you want to hear a sweet, tube-like top end, just pull out some RCA Living Stereo, Mercury, or six-eye Columbia jazz LPs that were recorded with tube electronics. If you want to hear an extended, linear top end with scads of detail, precision and harmonics, just put on a newer Chesky, Classic Records, DMP (like the previously mentioned Steve Davis Project), or Mapleshade recording and you’ll get it all.


The $1500 Belles 150A Hot Rod is my favorite amp for anywhere near its price and received a Reviewers’ Choice nod for its value. Comparing it to the 350A made an immediate impression. The extra $2000 the 350A costs gets you the obvious power increase of 150Wpc. But that’s an insignificant thing compared to the sonic improvement. The 350A is definitely not just a bigger version of the excellent 150A Hot Rod. The 350A is significantly more open and transparent. It offers better dynamics, detail, bass, remarkable midrange and treble presence while retaining the essential musical quality of the sound that makes the 350A considerably more than just the big brother of the 150A Hot Rod. The 350A conveys a sense of power, control and ease that the 150A lacks. Yet the 150A can make other sub-$2500 amps sound equally outclassed.

The Warner Imaging amps I’ve been enthusiastic about in the past, both the stereo and mono amps, are slower, sweeter, warmer, and less transparent. However, the Belles 350A shows these amps to be this way. You won’t notice that the Warner Imaging amps are anything less than exemplary in their transparency unless you hear the 350A. The Warner Imaging amps deliver more of a lush, romantic listening experience, which some people will pick every time. Others will prefer the more neutral and true-to-the-recording sound of the 350A. I’d always thought the Warner Imaging amps could stand shoulder to shoulder with the bass performance of any competitive amps -- until I heard what the 350A could do. The 350A’s extraordinary bass control just can’t be matched in my experience.

Reaching conclusions

The Belles 350A is the amp for audiophiles who want super-amp sound on an under-$4000 budget. It is a no-nonsense, yet well-finished amp whose sound is that of the recording unaltered. The 350A is for connoisseurs of accuracy and faithfulness to the original performance as it was captured to LP, CD or one of the newer high-resolution formats. There are no added colorations, no weaknesses that hide behind hyped detail or sweetened sound, something surprisingly few amps at any price can deliver. The 350A has a killer bottom end, and its incredible rejection of back-EMF from the loudspeaker ensures sound quality that is as true to the source as may be possible with current technology.

It doesn’t happen often, but every now and then a reviewer is lucky enough to encounter a product that is so perfect that it is difficult to imagine anything being better in any substantial way. But what is unusual about the 350A is that it achieves this at the lowest price point I’ve yet encountered. The Belles 350A is an instant classic, and if there is any justice, it will sell like hotcakes. It's definitely this reviewer's choice.

...Doug Blackburn

Belles 350A Amplifier
$3495 USD.
Warranty: Five years parts and labor.

Power Modules, Inc.
479 East St.
Pittsford, New York 14534
Phone: (716) 586-0740
Fax: (716) 586-4203

E-mail: info@powermodules.com
Website: www.powermodules.com

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