The Eddie Current Balancing Act Page 2

The Eddie Current Balancing Act

The Eddie Current Balancing Act is a transformer balanced headphone amp that can use 300B/PX-4 or 2A3/45 tubes.

That brings us to the item of discussion, the Eddie Current Balancing Act, a fully balanced input and output transformer coupled headphone/preamp featuring a 6SN7 input tube driving the user’s choice of 300B/PX-4 or 2A3/45 output tubes, switchable through the flip of a toggle on the back. The top panel slopes downward at an angle towards the front panel, in arguably one of the most unique designs ever featured for any kind of amplifier, much less a headphone amplifier, meant to recapture some of that original Moth aesthetic. The amp has myriad balanced and unbalanced inputs and outputs, with enough headphone output options to accommodate practically any kind of headphone, whether it is terminated in 4 pin XLR, dual 3 pin XLR, or ¼ in. Output transformers utilize Electra-Print’s Partial Silver Secondary transformers – using silver in the secondary of the output transformer is claimed to offer numerous sonic benefits such as increased micro-detail and resolution.

Unique to this headphone amp --- and any other headphone amp for that matter --- is the external power supply, which in addition to dual power transformers, two 6X4 rectifier tubes, and dual regulated B+ supplies, features an 18 watt 40kHz discrete power amplifier with current limiting that drives the filaments of the direct-heated output triodes with high frequency AC, rather than constant voltage or constant current DC. This is a key, and ultimately a huge part of what influences the sound of this particular topology, as the filament of a DHT and how it is heated has a huge impact on the sound. Craig believes AC heating to be superior to any other form of heating the filament, and counteracts the hum caused by traditional AC heating of the filament by using a 40khz AC signal, in which the “hum” created is outside the audible range. This kind of set-up is only featured in the most esoteric of amp designs, traditionally only reserved for the true hard-core DIY tube junkies, as the cost would be too prohibitive for most commercial implementations. Craig is able to do all the above for $3950, which when compared to some of the high-end options offered by Woo Audio or Todd the Vinyl Junkie is within the realm of “reasonable.”

Sound Impressions
I’ll cut straight to the core of my sonic impressions and flat-out declare this amp, easily heard within the first few minutes of listening, to offer the most expansive, most realistic soundstaging of any headphone amp I have ever listened to. Its damn right other-worldly, and is simply instant transportation into something very hard to describe but easily heard and felt. It’s a seamless soundscape that develops perfectly in front of you as a listener from wide left to wide right, without any sort of blob-effect in-between that occurs with lesser setups. The feeling is eerily reminiscent of being actually inside and absorbed into the sound, and I often found myself physically looking around to the left and right and behind me, as the aural cues from the recordings were conveyed with a sense of vividness and life. We could debate on what exactly about the design is most responsible for its soundstage presentation, (I personally give most credit to the AC filament heating), but honestly it’s probably a number of factors, from the filament heating to the highly regulated power supplies, and the partial silver secondary output transformers don’t hurt either.

Resolution is incredible and the amp really brought out details hidden deep underneath the recording (gotta love that little bit of silver in the output transformer). The Balancing Act was super-punchy and articulate, and would make any transistor-lover think twice about declaring that tubes, especially direct-heated-triodes, can’t do bass or PRAT. Ultimately, tube lovers value smoothness and tonal richness and the BA didn’t disappoint whatsoever. Mass strings were rendered beautifully and mass choirs were conveyed with stunning realism. The above impressions were through my Grado HP-1000’s, a set of Audeze LCD-2’s, Meridian 508.24, and a Firstwatt F1 and Lowther Dx65 Alerions for speaker usage. The excellent soundstaging characteristics were very obvious through my speaker set-up. The Firstwatt F1 is about as close to neutral as you can get, simply passing through whatever sonic impression is fed into it, and the Lowther DX65 is one of the most resolving and detailed of the 5” high-efficiency drivers. The soundscape, for lack of a better word, grew in depth behind the speakers, expanded inches outwards, while bringing the lead midrange a layer or two closer to you, providing even more three-dimensional depth.

The Eddie Current Balancing Act rear panel with multipe balanced and unbalanced ins and outs.

Tonally the amp was very dependent on tube-choice and overall tube-rolling. Craig sent me the 300B/PX-4 version with numerous tube options, ranging from AVVT, Sophia Electric, and KR Audio. The 300Bs from AVVT and Sophia Electric were very dense and rich, with the AVVT being somewhat dry and flabby down under, and the Sophia Electric just a bit tighter. The KR PX-4 was the perfect match for the Balancing Act, and to my ears was tonally perfect, providing some of the PRAT and drive that a tube like the 45 can offer, while still offering the tonal richness of a 300B, albeit not as exaggerated. My personal recommendation is stay with the PX-4 version of the amp, plug in a KR PX-4, and be done with it. I have listened to 300Bs, 2A3s, and 45s, and the PX-4, for lack of a better word seems to capture the best of what all three have to offer. While I have not heard the 2a3/45 version of the Balancing Act, my experience with Craig’s earlier Moth Si2a3/45H leads me to believe that one is still better off sticking with the PX-4 version as, like I stated before, you get a lot of the tonal richness of the 300B/2A3, with the articulateness and PRAT of the 45, while still being a very resolving and linear sounding tube.

The Eddie Current Balancing Act leaves nothing on the table, and is deserving of its title as a “statement” piece, offering the best design chops that Craig Uthus currently has to offer. Its price point of $3950 makes it competitive against its closest rival, which is the TTVJ Apex Pinnacle at $10,000, another fine sounding amp that offers similar functionality and sonic ability. The Balancing Act can accommodate all the inputs you would expect to have in a normal system, while offering excellent preamp functionality and pretty much will support any kind of termination that headphones are currently offered in. The soundstaging has no parallel with any other amp I have heard, and fits perfectly the core value of Craig’s design philosophy that audio gear should strive to transport the listener inside the music itself. Detail and resolution are extraordinary and with the PX-4 the amp is spot on tonally. Nothing else can be said on my behalf other than saying the Eddie Current Balancing Act is one of the finest commercial headphone amps I have heard, and I am positive any possible owner will find themselves extremely happy with its sound.

Resources Eddie Current's Balancing Act web page.
Head-Fi Balancing Act thread.

Eddie Current
23658 Clover Trail
Calabasas, CA 91302
(818) 224-3782

jvlgato's picture

Sounds like a really great amp. And having met the author, I can say that I really trust his ears. Great review, thanks!

dalethorn's picture

I was doing well in high school - well on the way to being a career criminal, where I could have afforded these things. But I reformed, and now my income is too low to purchase a $4000 amp. I look at this, then I can't sleep for a week. No wonder people go crazy.

Tyll Hertsens's picture

... you and me both, Dale.

But hey, I'm glad there's picture of Ferraris to gawk at ... and the Ferraris that go with them ... and the wealthy folks who buy them to make it possible to take pix.

At least I have a chance to listen to one at a meet.

I'll never get to drive a Ferrari.

(My FJR is pretty fast though.)

donunus's picture

I usually have my denial helmet on when listening to gear of this caliber. In this specific case, I would probably compare this with the low end ECSS solid state amp that they make and say hmmm its just a little bit better, not by much though hehehe :)

n_maher's picture

Excellent contribution, Ryan.

zippy2001's picture

I've heard several versions of the Balancing Act and have to say that this is the best headphone amp that I have had the pleasure of listening to. I really like it with the KR PX4 tubes, it is an extremely pleasant listen. I want one!