BackgroundThe following is a review and comparison of the Eddie Current Balancing Act and the Super 7. Craig Uthus of Eddie Current has been nice enough to lend Anaxilus and me the 2A3 and pre-production Super 7 for two weeks. Over this weekend, we also invited CeeTee down for a micro-meet to play with these toys. I've been trying to get him to spend more money. This is essentially a joint review with us comparing notes and me (Purrin) taking the lead on the write-up.
EquipmentDACs: Benchmark DAC1, PS Audio PWD
Headphones/IEMs: UERM, HD800, AD2000, LCD2r1, LCD3
Balancing ActThe Balancing Act (BA) could possibly be the best headphone amp on the planet - we at least believe that it's the best we have ever heard (I haven’t heard the Pinnacle, LF, or the Woo mono-strosities yet though.)
When I (Purrin) first took delivery of the BA, I stayed up until 2:30am every day for two weeks listening to it. Even now, every time I put on headphones powered by this amp, it’s always a "Holy <expletive><expletive> <expletive> Batman!" moment. There are only a few headphone amps that I’ve heard or owned that can compete in the same league: The WA5 (fully upgraded) and Apex Peak/Volcano (P/V).
The BA is priced at $3950 with new production EH 300B tubes. This is a steal when you compare it to some of the $10,000 amps out there. The WA5 is $4780 with the full upgrades including the Shuguang rectifier tubes. On that note, the BA does not need any fancy rectifier tubes. I rolled some TungSol 4x6WA to replace the stock rectifier tubes with no effect.
Much has been made about its soundstage - which is unsurpassed. I would refer readers to Ryan Clarin’s review on innerfidelity regarding the soundstage capabilities of the BA:
http://www.innerfidelity.com/content/eddie-current-balancing-act-page-2 Supposedly a lot of the credit for this goes to the high-frequency AC heater for the filament of the DHTs. No other headphone amp I am aware of takes this approach. (Someone please correct us if we are wrong.)
There are a couple of things however that we wanted to add about the soundstage. It’s not just soundstage width or depth as most of us typically think of it, it’s also the more subtle aspects of such as greater depth, precision layering of sound, and instrument separation. Musicians and instruments don’t come out flat or as one (or two) hazy blobs - they become distinct and three dimensional. This in turn affects all other aspects of the listening experience. The best analogy we can make is like how with HDTV, the elements in the picture just sort of pop out at you with better contrast and more vivid color.
The BA takes only one 6SN7 as the driver tube, which is nice because it alleviates the need for matched pairs. Two output tubes are used - the BA reviewed here was one that could take either the 300B/PX4. 2A3/45 and PX4/PX25 versions of the BA are also available. As of right now, there is only one good current production PX4 tube, and that is the KR PX4. The Sophia PX4 is a piece of junk - it lacks the richness of the KR. More importantly the Sophia lacks bass. Craig has indicated that the Sophia PX4 was really a 45 tube (same plate resistance and gain) disguised as a PX4. Comparisons of the pictures of the Sophia PX4 and Sophia 45 make us wonder. Finally the Sophia is not really a mesh either, more like a solid plate with little holes punched through it. In contrast, the KR just has much better tooling and looks to be much better constructed.
With a neutral driver tube such as the Tung-Sol Black Glass Round Plate and PX4 output tubes, the BA is a very clear sounding neutral amp with incredible speed and explosive bass. It’s almost solid-state sounding, but with the inner resolution and soundstage of tubes. One thing we noted comparing the BA to the 2A3, the Super7, and a few other cheap solid state amps we had lying around was that the BA is a very fast sounding amp. It’s scary fast given that it uses tubes.
Because most of the combinations of DACs and headphones that we were we running, we used the EML 300B solid plate output tubes to thicken things up a little bit. The EML300B is still fairly solid state sounding in the bass - tight and fast - just a slight departure from the PX4. More bloom in the midrange, not as clear sounding, and not as rich in the treble as the PX4. By the way, if we wanted a more classic lusher tube sound, we could have gone with the TJ Full Music 300Bs. The BA is still smooth and liquid sounding in the treble no matter the output tube.
The BA is by far the most dynamic amp I’ve heard, better than the Peak/Volcano which no slouch in this area either. The dynamic capabilities of the BA are excellent from throughout the entire audible range. The BA’s resolution and ability to extract low level information is also excellent. Whereas the Peak/Volcano is more analytical in this regard, the BA is more subtle. The P/V brings out micro-dynamics to the forefront. Personally I (purrin) prefer the BA more because it lets us concentrate on the music instead of the details. In fact – the BA forces us to listen to the music. The BA still gives to us the choice to examine the detail if we wish - but the BA always maintains a vector towards the musical performance.
Besides resolution and dynamics, there are important, subtle factors that really set the BA apart. These are much more difficult to describe because they are more commonly heard only on the "good stuff". The BA has a very immediate sound - of bringing us there to the performance and "in-time." It’s got a sense of authority and ability to dig into the music - that is of being able to instantly swing the intensity levels of sound in a way that’s very expressive. Perhaps the “phrase instantaneous dynamic-contrast” is a good way to describe it?
The BA provides us a continuity of volume levels - an infinite number of shades - very high granularity. This is akin to how a good CRT monitor or film projection screen is able to render to all shades of grey and dark rather than wash or blacken everything out (like on an LCD, especially the older generation LCDs.)
Finally the BA does have few weaknesses. Nothing is ever perfect. The bass is a little bit rounded - not as controlled nor tight compared to certain amps, i.e. (Apex Peak/Volcano, Dynahi, etc.) Do we miss this aspect of bass control? Yes, but the BA gets reasonably close enough and does so many other things better which suites our priorities. Some people may find the overall liquidity and treble smoothness of the amp unrealistic. The BA is not as analytical as certain amps. And the BA is not as lush and romantic sounding as would be expected of a tube amp. Finally it can be extremely costly to roll output tubes. The best 300B, PX4, and PX25 tubes can be extremely expensive.
