This review page is supported in part by the sponsors whose ad banners are displayed below

As headphone amp: With two pairs of Create 300Bs I was perfectly set for instantaneous A/Bs between BA and Woo Audio Model 5. The Audez'e LCD-2 recabled with Ken Ball's new eight-conductor round woven silver/copper leash is the best headphone in my collection. It clearly sails past beyer's T1 and Sennheiser's HD800 (also recabled) and with quite a lead. I'd thus focus on the planarmagnetics and only invoke HifiMan's HE-6 to report on gain sufficiency into very inefficient headphones. For a reality check against transistors meanwhile I'd sneak in Burson Audio's $1.100 HA160D. In combination with the LCD-2 (and iPod with Onkyo ND-S1 digital-direct dock) I'd crowned that my Favorite of 2010 hardware. For thrice the dosh but no 24/192 S/PDIF and 24/96 async USB DAC of high quality, the BA in this context would have to compensate elsewhere to become more than exotica.


300B vs 300B: Though running identical output glass, the Eddie Current and Woo amps sounded quite different. The Woo became the ModWright of the first preamp session. It was dense, chewy, robust and clearly drier and more damped. The BA had more top-end sparkle, air, space and decay gossamer. The Woo was stronger on bass and accordingly also darker. The Eddie Current was more illuminated in both directions - inward as greater insight into and through the musical weave; and outward as transmission of more energy. This also created higher magnification on tone modulations and shifts in timbre. The Eddie Current was the leaner more ripped operator.


In this juxtaposition I couldn't in good conscience give either machine any demerits on 'negative 300Bness' as I'd done in preamp mode vis-à-vis the PX4. The BA was simply the more liquid, the Woo the more massive flavor. Perceived issues of opacity, slowness or thickness didn't factor. I'm not certain why except to say that the LCD-2's raw resolution is so ahead of the game as to suffer fools far better than lesser devices. Clearly Craig's leaner more transparent voicing makes the BA perfectly suitable for rolling in some vintage 300Bs of Western Electric and TJ/Full Music caliber to move sonics into the Woo amp's direction if one wanted to.


PX4 vs. 300B: As over the speakers with an interceding transistor amp but even greater in magnitude now, moving the BA in headphone mode from Create/Snyergy 300B to KR Audio PX4 hit a light switch. The entire sonic landscape opened up. In Highlander speak this was the quickening. In corporate takeover lingo it was expansion. To borrow from an earlier 45 SET review, it was that quasi hallucinatory heightened-state type of clarity or suchness where one seems to see everything simultaneously but rather than getting confused or overloaded from hyper rez one stays serene, present and in the zone. Them are fighting words. But Joe Eagleeye was right. All I can add is that like love, when it happens you know. I'd also add that to my ears the PX4 magnifies what makes the Balancing Act special. Even the best 300B moves it back again just a tad closer to more ordinary normalcy.

Gain: In its highest setting the Weiss DAC2 puts out 5.48V max. That equated to a ca. 14:00 volume setting with the HifiMan HE-6 (the Audez'e played equally loud at high noon). In both 1.35V and 1.78V mode I flatly maxed out the BA on the HE-6 to suggest that an industry-standard 2V-out digital source is really borderline. The 2.74V setting worked fine at about 16:30 but on classical music with a low recorded median even that could prove insufficient particularly if you enjoy high SPL. In short the Balancing Act will properly drive the most inefficient headphones if you precede it with a source that puts out a minimum of 4 volts.

Tubes vs. transistors: With both the BA and HA160D fed from the Weiss DAC, the transistors were edgier and sharper with just a slight propensity for brightness. When I switched output devices in PureMusic to USB DAC however and ran the Burson from its own asynchronous USB input, this changed. Now it and the Weiss/Eddie Current combo were on equal footing. The PX4 did more audible space on decays which to some could suggest tube microphonics. Without airborne disturbances from fullrange loudspeaker—those could incidentally be addressed with Pyrex chimneys around the valves—microphonics would have to get triggered by physical impacts to the amp chassis. Obviously I didn't commit those. Whatever the cause, the direct-heated triodes had the edge on dimensionality not in terms of lateral space but by injecting more air between the stage actors.


In terms of tone color intensity (what valve speak calls saturation) it was a draw however. Tube supremacists will scoff at that as impossible yet it's precisely why in my big rig the Burson as DAC (volume control wide open) has displaced the Weiss. Here the class A HA160D simply had the same inside-out tone 'pressure' as the PX4. Meanwhile the outsides of the tones were drier or more damped where the valves were a tad looser or fluffier. Talking of insides and outsides of tones as though they were translucent soap bubbles is ridiculous of course. As long as the subjective response of sonic differences translates for someone who wasn't there, all is well however.


Take the absolute must-own album Cigala y Tango (must-own if you loved Lagrimas Negras that is). This is a live concert cut like Blanco y Negro. With the audience applause the BA had more energy sparking off the clapping hands into the venue. On fast flamenco guitar runs, the Burson was sharper and more percussive. On Diego's glorious vocals, both were equally saturated and intense but the HA160D focused more on physicality, the Balancing Art more on presence in space. This small difference was symptomatic and arguably the core distinguisher. If we build up a polarity collection like piling weights on a scale, we'd do damped/loose, robust/airy, focused/spacious, transients/decays, compact/expansive. This properly bypasses tonal balance, harmonic distortion and obvious colorations which weren't in play. These polarities instead point at the predominantly textural differences as long as we remember to paint with a fine brush.


The Burson's powerful resistance to go packing and cede the ground to the $4.000 challenger reinforced my admiration for it. Those who prefer the BA—and I could imagine many would—ought to admit that their preference comes not only at quite the price but really is no clear-cut victory of 'better period '. It's nothing but personal taste. That said, once we leave the Audez'e behind and reach for designs more in need of tonal assistance (I'm thinking Sennheiser HD800, AKG K702), the Balancing Act's particular contributions at least to my ears become more necessity than luxury. The Burson/Audez'e combo is simply one of those where everything sums to quite transcend the individual parts.


Balancing out this act: Craig Uthus' direct-heated triode machine is headphone amp first, preamp second. That's not slighting its performance in the second application. It's simply a reflection on equivalent—similar if not identical—results being possible with rather less costly passive volume controls of Bent Audio Tap-X or StereoKnight Silverstone caliber. As headphone amp, the Balancing Act overtakes the fully optioned-out Woo Audio Model 5 on resolution, illumination and finesse. That puts it right on top of Mount Olympos.


Whilst the power supply could mildly hum on occasion only to be dead quiet on others (hello vagaries of AC power delivery), the actual signal feed into speakers or headphones was never anything but perfectly quiet. The BA is an ideal showcase for the legendary—oft invoked but rarely delivered—linearity and low distortion of triodes. That's because it doesn't attempt any heavy lifting involving high current and extremely low output impedance. It bypasses the entire hit 'n' misery of low-power triodes and speakers. It presents these output devices with an idealized environment to truly shine. Enter line-level or headphone drive. This elegantly eliminates the usual gross colorations and limitations. It gets us down with what these bulbs can do when they're liberated from mundane worries. This is probably as close as one can come to encountering their pure essence.

In the case of the PX4, that bottle then gets elevated to the purity, directness and speed of premium transformer or autoformer volume controls. What still distinguishes the glowing glass was described above.


In the case of the 300B by comparison one should conclude that its standing in the DHT community has been quite overrated. Against the PX4 best of breed 300Bs are instantly delegated to second tier even under such idealized conditions. From personal familiarity I'd add the 45 and VT52 to the list of 300B killers. Friends of mine deeper into exotic tubes also mention the AD1 and 50.

To wrap up and considering the competition, the Eddie Current Balancing Act is a clear Blue Moon Award winner as a headphone driver with first-class add-on preamp functionality. While limited to XLR outs as delivered for review, the customizable nature of its boutique origins probably means that a customer wishing RCA pre-outs can be readily accommodated. Those into balanced-drive headphones with custom wire harnesses (either dual three-pin XLRs or single 4-pin XLR) also have in the Balancing Act the perfect platform to experiment. With sufficient gain for even the beastliest current production cans if the source can swing 4 volts or more, it's also an equal opportunity platform. $4.000 for a headphone amp is admittedly way off the reservation for any but the most fully committed... until we remember reader Joe Eagleeye. Let's quote him again for the catchiest true closure on this assignment:


"I've got the Audez'e LCD-2s (recabled with Stefan Art Audio's balanced Endorphin wire) with an Eddie Current Balancing Act headphone amp. The sound is spectacular. My source is the Metric Halo LIO-8 pro DAC which is quite the rage on computeraudiophile.com. That replaced a Weiss Minerva and a tweaked Technics SL1200 turntable. I lost my listening room which prompted the move to headphones. I haven't regretted it for a moment. I used to have Avantgarde Duo Omegas and Shindo electronics in a 1,500sf open loft." Indeed. I'd say the same for the BA/LCD-2 combo if circumstances forced me to abandon my big system anchored by Franck Tchang's fabulous ASI Tango R speakers.
Quality of packing: Good. Ships in two separate cartons.
Reusability of packing: A few times.
Ease of unpacking/repacking: Easy.
Condition of component received: Flawless.
Human interactions: Very transparent on technical questions but not very savvy anticipating user issues due to lack of communications.
Pricing: High for the headphone amp genre, merely lower mid level for valve preamps.
Final comments & suggestions: As delivered the RCA outputs are unlabeled but fixed to bypass the volume, output selector and on/off switch. Production will henceforth label them as such and also explain this feature in the owner's leaflet. This machine can be delivered for 45/2A3 or 300B/PX4 operation but not both. Lack of remote control could be a deal breaker where preamp applications are dominant over headphone use. As preamp the 300B exhibits similar sonic thickening as we know it from speaker drive. Particularly in a modern high-resolution context the PX4 should be far peferable. In headphone use meanwhile, many loads will benefit from the tonal colorations of the 300B. With this amp you can have it both.

Eddie Current website
Enlarge!