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Reviewer: Srajan Ebaen
Source: Zanden Audio Model 2000P/5000S; Raysonic CD168; Ancient Audio Lektor Prime; Abbingdon Music Research AM-77 [on loan]
Preamp/Integrated: ModWright SWL 9.0SE; ModWright LS-36.5; Music First Audio Passive Magnetic; Bel Canto Design PRe3; Wyetech Labs Jade; Supratek Cabernet Dual; Melody HiFi I2A3; Eastern Electric M520; Yamamoto HA-02; Trafomatic Audio Experience One [on review]; AMR AM-77 [on review], Red Wine Audio Signature 30.2 [on review]

Amp: 2 x Audiosector Patek SE; 2 x FirstWatt F4; Yamamoto A-08S; Bel Canto e.One S300; Fi 2A3 monos; Coda CX and CSX [on review]
Headphones: AKG K-1000 w. hardwired Stefan AudioArt harness; audio-technica W-1000
Speakers: Zu Cable Definition Pro in custom lacquer; Mark & Daniel Ruby and Maximus-Monitor with Omni-Harmonizer; WLM Grand Viola MkII Monitor with Duo 12 passive subwoofer, Duo amp and Sys V active crossover; DeVore Fidelity Nines; Rethm Saadhana

Cables: Crystal Cable Ultra loom, Crystal Cable Reference power cords; Zanden Audio proprietary I²S cable; Zu Cable Varial, Gede, Libtech and Ibis; Stealth Audio Cable Indra, MetaCarbon & NanoFiber [on loan]; SilverFi interconnects; double cryo'd Acrolink with Furutech UK plug between wall and transformer
Stands: 2 x Grand Prix Audio Monaco Modular 4-tier
Powerline conditioning: 2 x Walker Audio Velocitor S fed from custom AudioSector 1.5KV Plitron step-down transformer with balanced power output option
Sundry accessories: GPA Formula Carbon/Kevlar shelf for transport; GPA Apex footers underneath stand, DAC and amp; Walker Audio Extreme SST on all connections; Walker Audio Vivid CD cleaner; Walker Audio Reference HDLs; Furutech RD-2 CD demagnetizer; Nanotech Nespa Pro; Acoustic System Acoustic Resonators
Room size: 16' w x 21' d x 9' h in short-wall setup, with openly adjoining 15' x 35' living room

Review Component Retail: $1,949

Déjà vu all over again? Reverse engineering? These concepts collided in the JAS Audio Bravo 2.3. Hadn't I just applauded Almarro's A318B, an 18-watt 6C33C SET from Japan selling for below $2,000? Now China retaliated by adding remote volume, user-adjustable negative feedback, auto bias and a tube cage while asking $1,949. Reverse engineering -- more like back tracking -- its flight path to Larnaka/Cyprus showed Global Village tentacles. The planes had flown via Poyle/Great Britain, Paris/France, Memphis/Tennessee, Anchorage/Alaska, Lantau Island/Hong Kong to finally arrive at the box's drop-off location of Tsuen Wan, Hong Kong. The shipping papers named Dignity Interl (HK) Ltd in Mongkok Kowloon's 56 Dundas Street as the shipper and point of origin respectively. Why FedEx hadn't chosen Dubai as the single stop-over necessary to bridge HK and Larnaka remains a mystery.

No mystery at all is why Steve Monte of NAT Distribution and Quest for Sound should have solicited this review. He is JAS Audio's US distributor, replacing Opera Audio Consonance which he previously represented. If Steve wanted to reverse-engineer the Realsization Award I had bestowed on Almarro's overachieving A318B, all he had to do was submit a machine based on the same concept, the same output tubes and the same price class. Unless his maker had somehow fouled up a proven recipe, Steven's plan was destined to succeed. Staring at the Bravo 2.3 in the flesh looking rather better than its web photos, I confess that thoughts of feeling predictable and getting manipulated raised their gnarly little grimaces. Yet there was nothing in the least untoward about any of this. Just timing. Had I not volunteered for this assignment after nobody else on staff proved available or interested? In the end, budget-conscious high-performance hunters deserve another discovery in the valve integrated sector that offers sufficient power and current to drive a wide range of realistic speakers. Don't blame the messenger should the outcome turn out wholly predictable.

I don't believe politics belong in audio discourse. When it comes to Sino goods, the savvy shopper insures that quality distribution and customer support will accompany one's investment into the future, all matters for personal due diligence. And to be clear, the use of the term reverse engineering was entirely tongue in cheek. Nobody owns exclusives on basic single-ended tube circuits ending in 6C33Cs. Should such designs enjoy undue commercial success -- the precedents of Lamm and BAT in particular make this very much the case -- it's simply good business sense to stake one's own claim on this turf, especially when the most famous proponents cost serious money; when one's own infrastructure allows one to offer superior value; and when a prior such high-value example was greeted with great fanfare. Looking at the Bravo 2.3, you'll easily forgive the redundancy of High End Valve Tube Amplifier of the transformer cover's wood engraving. Unless JAS Audio meant to imply tubes squared. In which case the last laugh could be on our friends from Kowloon even on this detail.

While the companion JAS amps in the new Bravo line duplicate the tranny wood cover also for the tube deck, the 2.3's potent 6C33C heat radiators suggested against it. The second wooden dress panel thus finds itself wisely replaced with translucent acrylic. That telegraphs the black chassis paint underneath with its red silk screen of model name and tube types: 5AR4s between the 6C33C power triodes, Russian 6J4P (6AU6, EF94) drivers preceding the rectifiers.

The guts show the motorized pot tucked beneath a small green PCB and dual-mono choke filtration.

The tube cage removes by loosening four bolts. It fits tight enough to eventually scratch chassis paint. This warrants a minimum of removals, practically speaking just one to insert the separately packed valves and then leave it off.

The frontal controls are surrounded by clock-type markers and fitted with a miniature pointer to confirm setting. The IR eye for the remote sits above the negative feedback control which, contrary to expectation perhaps, reduces clockwise and thus begins with the highest possible NFB value. Minimal feedback potentizes dynamics but also energizes the treble. Chances are, most listeners with modern speakers will have this control set to at most high noon.

The binding posts offer the usual 4- and 8-ohm tabs and are quality CMC USA issue. Four line-level RCA inputs and the customary IEC power inlet with mains fuse holder round out the back panel features.

Concluding visual inspections, the Bravo 2.3 is wrapped in classy though not overdone threads; avoids the garish blue power LED in favor of an elegant mute yellow; ditches the nearly de rigeur lethal weapon called heavy-duty metal remote for a credit-card lightweight version that works splendidly; and is electrically perfectly quiet over 101dB speakers, with the barest of mechanical hums issuing from the transformers when the ear hovers right above a 230V machine condemned to a 240V feed that's been measured to fluctuate as high as 260V. That's flawless noise performance.

The number of amps running 6C33Cs, at least outside Russia, is far smaller than the more recognizable 300B, 2A3 and 45 triodes. One reason could be price. Industrial 6C33Cs are dirt cheap by comparison to designer triodes. They lack bling and nostalgia. Another could be the valve's fluctuating operating parameters. This includes gain which requires close matching (the reason why Almarro's A318B added gain trim via bias adjustments despite the circuit's fixed bias). One designer I talked to is so enamored with the 6C33C's sonics and likewise so annoyed by its potential for extreme bias drift that he designed a sophisticated servo circuit for his bias supply. It's the amp he listens to personally. Yet he refuses to go commercial with it. He favors other valves for his consumer products. Since WLM became the Almarro importer for German-speaking Europe earlier last year, more than 60 Almarro 6C33C amps were sold, no tube stability problems reported. As always, implementation is key. The most hi-profile commercial 6C33C amps in the West are by Lamm and BAT. Warning signs of 6C33Cs aging are intermittent transients through the speakers; dulling tube getters; and unsteady bias. Replacement tubes will be of very low cost and it's advisable to keep a few on hand. While the 6C18C is a drop-in substitute, reliability is purportedly dubious so stick with proper 6C33Cs.

This tri-nipple valve is a high-conductance or high GM tube for lower voltage and higher current swing than for example a 300B. The 6C33C's internal resistance is very low, hence its many appearances in OTL amps where transformer impedance matching is omitted. Because 6C33Cs run hot, proper cooling of ideally top-quality tube sockets is mandatory for longevity. Filament wires, solder, bias resistors and bias trim pots must be of high quality. For some, this could preclude feeling comfortable with affordable 6C33C amps from companies without any prior track record valve for electronics like JAS Audio. Plate dissipation of up to 60 watts is possible but most designers will advocate 50 watts tops, with ca. 200 volts on the plate and about 200mA of plate current. A 6C33C takes about ten minutes to operate at proper plate current and a delayed turn-on protocol built into a proper amplifier circuit will avoid overheating the anode. Additionally it's sensible to not play your most stressful blockbusters immediately but to wait for half an hour. This should extend life expectancy for the output tubes.

It's uncomfortably easy at times to blame certain behavior on components when one lacks the ability to distinguish between external and internal factors. My AC in Cyprus is supposed to be 240V but tends to be higher. This can cause transformer hum which might not be replicable at 240V on the nose. A voltage regulator could stabilize the wall AC but my one experience with such a device had been sonically so disastrous that, prematurely perhaps, I've given up on the whole genre. To the point, the Bravo proved stunningly quiet on certain days, not so on others. It never got bad but on sub-optimal days, the amp wasn't as quiet as the Almarro A318B had been. Would dedicated 240V transformers rather than the supplied 230V have stabilized this variability?

Like the Almarro and thus perhaps a signature trait of the output tube -- experienced 6C33C fanciers might agree or not since implementation remains the moving target to require familiarity with a wide range of implementations before making accurate wide-ranging statements -- the Bravo 2.3 is texturally drier but considerably ballsier than a 300B. Unlike most 300Bs in my experience, its flavor is far less midrange specific, more full spectrum and rather more extended in the treble. It thus lacks the peculiar emphasis 300Bs can shine on the vocal range. The tonal fabric is more of a piece. The top end seems to benefit from proper application of feedback at least in the two circuits I've heard to avoid a potential for glassiness. At first I was bothered that I had to elevate the volume for the curtain to rise. It's something my Rethm Saadhanas' 98dB Lowthers categorically don't need. They already paint the full picture at whisper volumes - if an amp's fraction of the first watt is up to it.

This initial reticence mellowed with break-in. Another (non-audible) break-in phenom involved the wooden dress plate. It is attached to the transformer casing in the corners, with the mounting holes disguised by wood filler. Perhaps due to adjacent heat, this dress plate began to bow a bit in the middle. Only long-term ownership can settle this conclusively but I question whether wood belongs anywhere on this 6C33C amplifier (the earlier wooden deck plate shown above having already been replaced by acrylic). Heat exposure and thin 'floating' wood panels don't seem quite the happiest of bed fellas.

To keep observations on raw resolution honest, the Bravo 2.3 was squared up to the FirstWatt F4 and Red Wine Audio Signature 30.2 on my Rethms. My Raysonic Audio CD-168 with Mullard bottles and variable outputs became a financially matched source of choice to accommodate the volume-less amps and the more expensive Ancient Audio Lektor Prime CDP/preamp saw duty as well. Compared to the F4, the Bravo wasn't as preternaturally separated and resolved. Distances between notes were smaller. If you've ever studied music scores with dense clusters of 32nds crammed into a few bars, you'll appreciate how more space between notes is welcome. The Pass amp also had the literal edge on bass articulation. At this level of the game, with very revealing but non-challenging speakers, the magnitude of differences was minor. The JAS Audio piece played it a tad looser and fluffier and its delineation of outlines was a touch more watercolor than the crisper acrylics of the Californian. On the flip side, the tube amp was a bit weightier and heavier. While spatially not as capacious, its colors were somewhat deeper - what I think of as inner pressure when notes feel more like ripe fruit. The uppermost treble of the Pass amp was more refined and smooth, its overall demeanor tauter.

What I took away from this comparison was admiration for the Bravo's surprising similarity to a world-class transistor amp in overall linearity. Granted, these first speakers use self-amplified sub-75Hz bass systems and their 98dB Lowther DX-55 sensitivity presents little drive challenge. Still, in such a non-stressed context, the Bravo 2.3 proved fantastically quiet and honest while injecting tube density and color 'pop'.

With the 91dB DeVore Nines and at 2:30 o'clock on the dial under max feedback, the Bravo 2.3 was matched how most prospective buyers likely would - to a sensible, fully passive load of appropriate sensitivity and bass artillery of twin 6ers per side. As its review described, John DeVore's 2.5-way is a highly linear and resolved loudspeaker with very taut and punchy bass and an accurate rather than hedonistic take on proceedings. To fill out its frame for pleasure seekers requires nothing more than the $2,500 Red Wine Audio Signature 30.2, a battery-powered class T amp of uncommon attributes.

In the 'meat-packing' department, the Bravo 2.3 out-packed even the RWA unit, an across-the-shelf action that included the low bass for yet greater mass and pounding when massed rolls of African drums on Jamshied Sharifi's A Prayer for the Soul of Layla [Alula 1005] demanded it. For those relating to the Nines as desirous of more body, these 6C33Cs are tailor made. How exactly they pull it off without defaulting into editorializing or artificial warmth is an excellent question. Compared to the Tripath amp, the JAS Audio unit had more tone saturation and forward projection as though the musical reins were pulled tighter and gathered up. That this action gets more pronounced in the amp's higher gears such as the DeVores invoked over the Rethms points at a power sweet spot. In other words, the Bravo isn't as much a first-watt amp as certain other SETs in my arsenal.

The same sweet spot was entered by my WLM Grand Viola Monitors. This supports conjecture that the Bravo 2.3 circuit comes fully alive at output levels beyond your typical direct-heated triodes. It thus isn't a complete stand-in for 2A3s, 300Bs or 45s. Instead, it's the "next size up" option that sounds best when used without being strangulated by a barely cracked-open throttle.

The horn-loaded twin-tweeter array of the WLMs also confirmed again why the Bravo makes its NFB zero setting the default maximum. With that control fully opened for minimal feedback, the treble gets frisky, even hairy on certain material - the aforementioned glassiness that goes beyond "lit up" into slightly objectionable turf. Below 12 o'clock on the feedback dial, this is controlled. On a speaker like these deceptively harmless-looking WLM monitors and with material like Ojo de Brujos' latest [Techari Live, Pias 015], the Bravo 2.3 is fully in its element. With this hi-energy live fusion of Cuban brass and piano, impossibly fast Latin rap, Flamenco rumba, the Reggae hit "Get Up, Stand Up" undergoing the Ketama morph, Martirio injecting Cante Jondo screams, turntable scratching, conga and tabla duels, the name of the game is perfectly timed attacks.

This calls for taut upper bass delivered in dry, no-flab punches. Like the Almarro before it, the JAS Audio integrated presents this as a particular forte of the 6C33C. It refuses to go soft when the shelling commences in the 100 - 300Hz band that's vital to convey drive and rhythmic fidelity. Where the usual small-power triode starts its magic in the midrange or perhaps the treble, this amp seems to begin in the upper bass and spreads out from there. Those looking for limpid fireside romance will find the sound too fresh and muscular. Those who find 300Bs too specialized and unfit for the hard-hitting stuff will be thrilled.

The remote worked well without jumping hence smooth gradual increases or decreases of volume were easily achieved. Let's collect impressions then. Mated to suitable speakers, the JAS Audio Bravo 2.3 is an uncannily lucid and apparently linear performer with terrific timing. Rather than lit from within, it's pressurized from within. The former is most typical of deep triode. There the PX25 arguably remains king from among personal encounters. The pressure sensation combines the mass one expects from push/pull circuits with the quicker, more gathered-up gestalt of proper SETs. Put differently, the sound is similar to a superior tube-pre/transistor-power combo where the solid-state amp isn't too dry. That the Bravo 2.3 can combine those qualities in a single enclosure should appeal to smart shoppers who don't need much power.

As someone who presently favors the modern Emission Labs 45 direct-heated triode for its crystalline purity and speed over all other DHTs, the two 6C33C amps I've listened to add control and drive to that recipe without unduly shifting the overall gestalt of the performance. To my ears, it thus makes the JAS Audio Bravo 2.3 into a kind of "45 with muscle" amp where bottle cost is far friendlier than my fave EML 45s. This negates concerns over tube replacements. The only reservation one might entertain is JAS Audio's present lack of track record. We know nothing yet about long-term reliability for their Chinese-built tube amps to preclude special merit considerations. This area of due diligence, on dealer or distributor service support, is for the customer to perform.

If your domestic market checks out satisfactorily in that regard, the JAS Audio Bravo 2.3 gets a strong recommendation not simply as 'starter kit' for the tube newbie but as a serious performer for speakers that sing on 10 watts to leave some dynamic headroom. If you've been curious about the world of direct-heated famous triodes but didn't know where to enter that world, I'd leapfrog the 45s, 2A3s and 300Bs in favor of the 6C33C. They're cheaper, more powerful, deliver more current and control and thus are altogether more applicable for DeVore-type 'conventional speakers with inbuilt valve friendliness'. They're also more accurate and transparent than most thicker, slower, somewhat elephantine 845 implementations. For single-ended and if you can only have one amp, the 6C33C might just offer the most attractive combination of virtues. The JAS Audio Bravo 2.3 enables an apparently painless path into this sector and the inclusion of both a substantial tube cage for domestic approval and remote volume to make the Year 2008 cut covers practical essentials. JAS makes a promising debut with their two-point-three times bravo!
Quality of packing: Double cardboard with massive foam end caps.
Reusability of packing: At least once.
Ease of unpacking/repacking: Easy.
Condition of component received: Flawless.
Completeness of delivery: Power cord, manual, screwed-on tube cage, tubes separately packaged in cartons or bubble wrap.
Quality of owner's manual: Basic.
Website comments: Sufficient but could benefit from an overhaul.
Warranty: 3 years.
Human interactions: None were required but US distributor Steve Monte's track record in that regard is excellent.

Pricing: Affordable.
Final comments: The tube cage mounting scheme is liable to scratch the enclosure with repeat use. A preferable solution might be banana fittings. The wooden transformer cover dress plate bowed a bit.
Manufacturer's website
US importer's website