In our last episode of High Efficiency Adventure, the review of the Zu Audio Union loudspeaker, I spoke with delight about the 2A3 Classic Mk2 power amp mated with the very high efficiency Zu speaker. To review, I wrote:
my review of the EL84TT, Carl Ng offered to send me their 2A3 Classic Mk2 stereo
power amp ($2888 CDN). It had arrived that same day and while Tom listened to
classical music I cut open the box and inserted the tubes. It uses a pair of
Sino 2A3C (a new variant of the 2A3) from Guiguang, rumored to be a sister
company of the more widely known Shuguang, and it is favored by Carl for its
sound, fit, looks and price. It looks like a 2/3 scale version of a 300B —
larger than you might expect for its 3.5 watt output. The rectifier tube is a
NOS Mullard GZ32 favored by many, but easily replaced thanks to Triode Lab's
unique "Uni-fy rectifier stage" to tune the amp to your preference.
And the 6SN7 tubes are OTK Military Grade which is the cheapest 6SN7 you can buy
but accurate, neutral and laid back. The amp is Class A with an auto-bias
circuit and unusually, it is AC heated by preference. Triode Lab also makes a
hot rodded 2A3-S special edition for $3888 CDN with premium transformers and a
chassis that will likely satisfy your desire for audio jewelry. The S version is
for the connoisseur who not only likes to roll tubes, but roll amplifiers as
We put the CD
into forward, listened for a brief moment, looked at each other and
simultaneously broke out into laughter. This is a seriously good amplifier
in spite of its humble appearance. The top end is rolled off. The presentation
is dark, being centered on the lower midrange with a full, sumptuous bass.
Attack is good, decay is long, midrange focus is very good and the holographic
music grabs your gut and pulls you right into the collective soul of the
performers. Forget about a subwoofer. With the highs rolled off and the ripe
mid-bass you don't miss the lowest octave because you're so emotionally
engrossed in the music. In fact, if I wasn't so indoctrinated in the philosophy
of the so-called high-end audio, I could call this an end game and move on to
another hobby called high fidelity all the while enjoying the music. Should
I put this paragraph to rap music? No wonder Carl tells me a lot of his
customers with Zu speakers own this amp. These could be the 3.5 most important
watts on the planet. And if not these watts, I'd be tempted to ante up for the
2A3-S. (Can you hear me now, Carl?) Combined with the transparency, dynamics and
focus of the Zu Union, you get all the pace, rhythm, timing and timbre that's on
the recording. You ask about the Chinese Drum cut? It barely required more than
the first watt yet the Triode Lab delivered as much slam and more delicious
timbre than I've ever heard from this piece. Tom went home about 11 pm and I
fell into bed at 2 am after "just one more song".
Well, Carl Ng heard me, all right. But had I painted myself into a corner with the rave remarks about the Classic Mk2? The adventure continued as it had before with Carl hand delivering the 2A3-S to my home. I was excited because I expected it to be a lot better than the Classic Mk2 and the suspense over which color he would deliver was over-stimulating me. It comes in either Mercedes Benz Design Tri-Coat White or Porsche Bordeaux/Rubin Red. Both appear luscious in the photos on their website, though the white is clearly the more understated choice. I would have loved either. As I pulled the amp from the red silk-like bag with Triode Lab logo and "Made in Canada/Fait au Canada" silk-screened on it, my eyebrows twitched upward and a subtle smile came to my face. It was Porsche red with mat black paint and gold emblems on the James transformers and a gold Triode Lab emblem on the front face. The Cardas RCA connectors and the speaker binding posts out back were also gold plated. Simply beautiful!
I had suggested to Carl that he add wood side
panels like I had seen on other amps on their website, but what he came up with
was rather ordinary looking thick blocks for the review sample. The revised Plan
A would be to call Chris Harban at Woodsong Audio out in Idaho. Chris
specializes in Linn LP12 turntable plinths that are visually stunning. He
indicated to me that side plates for amplifiers would be easy for him to make.
They won't be inexpensive ($175 to $250), but the 2A3-S and the higher end
Triode Labs amps will be taken to the pinnacle of design by adding them.
2A3-S uses a pair of Tung Sol 6SN7 GTB tubes from Russia rather than a more
generic 6SN7 tube that is also sourced from Russia that came on the Classic Mk2.
I used the very same CV 593 rectifier tube and 2A3C tubes with gold pins in both
the Classic Mk2 and the S versions although they suggest you can use a variety
of rectifier tubes to fine-tune the amplifier. Other sonic differences come with
the use of the very finely crafted James Audio Transformers and the Mundorf
Silver/Gold/Oil capacitors in the 2A3-S. I've already indicated in the Zu review
(quoted above) that the 2A3 Classic Mk2 is considerably different sounding than
the previously reviewed EL84TT integrated amplifier but let's delineate some of
the basics of these amps so you don't become hopelessly entangled in the
Uses Hammond output transformers, Hammond choke filter, Hammond power
transformer, Mundorf ZN Tin Foil capacitors and EL84 tubes. It is an integrated
amplifier with a passive input stage, putting out 6 watts per channel.
Mk2: Uses Tomiko Kyushu Output transformers, Hammond choke filter,
Hammond power transformer, Mundorf ZN Tin Foil capacitors and 2A3 power tubes.
It is a power amp that puts out 3.5 watts per channel.
2A3-S: Uses James output transformers, James choke filter, Hammond power transformer, Mundorf EVO Silver/Gold/Oil capacitors and 2A3 power tubes. It is a power amp that puts out 4 watts per channel.
The Zu Union speaker was used to review all of
these amps, sometimes in conjunction with a pair of prototype Tekton Design
powered subwoofers that were connected via speaker cables from the amplifier
(not with a line level input from the preamp). This coaxial Zu speaker with a 10"
nearly full range driver and a concentric tweeter that crosses over at 12 kHz
was short lived. Product improvements using nano coating of the 10" cone and
improvements in the minimal crossover to the (super) tweeter improved the
majority of speakers in the Zu line. This brought the updated Soul model ($2000)
very close in sound quality to the Union. The difference in price did not
justify the difference in sound, so they kept the less expensive updated Soul
and dropped the Union. This is important, because my comments should be taken in
the context of the older Zu speakers, not the current production that reportedly
has a smoother upper treble. I haven't heard any of the new Zu speakers, but it
is a typical case of the good just getting better and better — something that
happens with regularity in this hobby. Using even more costly amplification than
we're looking at here, I achieved outstanding results with the Zu Unions and
gave it a Blue Note Award for 2013.
Moreover, the missing upper treble becomes more apparent when using a subwoofer, causing the center of the spectrum of the music to shift toward the lower midrange. As I said in my review of the Zu, the speaker blends very nicely with subwoofers because it drops off cleanly and quickly when the speakers are placed out into the room away from the walls and corners. The downside of adding a subwoofer here is that the missing upper-treble becomes more noticeable with the additional mid and lower bass information. So it's a bit of a trade-off. The quality of the mid and low bass coming from the subwoofer when fed directly from the power amp with speaker cables was taught and dynamic — much better than I expected coming from a 4 watt SET tube. As for the volume of the mid and lower bass, that is controllable with the twist of a knob on the back of the subwoofers. Suit yourself. But if you should have a larger speaker that digs down into the 20-30Hz range your only recourse for controlling bass output will be in positioning the speakers in the room. If you have such a full-range speaker, you may want to consider selecting the ZN capacitors that will give you a more prominent top end to balance off the deep bass.
other minor shortcoming I found with the 2A3-S is the somewhat diminished
dynamics when compared to the 2A3 Classic Mk2 and the EL84TT. The attack of the
notes and the hard rim shots literally leap into the room with these other amps,
contributing to their greater sense of transparency and dynamics. Such dynamic
drive also commands more attention to the music and it can wear you out more
quickly. The 2A3-S was always pleasurable — never irritating or tiring. Carl
readily admits that this is why so many of his customers prefer the 2A3-S with
their Zu speakers. He also suggested the difference lay in the transformers. He
sensitivity [of the Classic Mk2 and the 2A3-S] is the same, just the output
transformer is differently designed in its approach and presentation. The Tomiko
[in the Classic Mk2] might sound louder at first, but could be breaking up
faster in max volume. Whereas the James comes in nice and smooth, then gradually
increases its loudness. On measurement, the James is supposed to be better,
whereas the Tomiko is less ideal (more edgy on the curve seen on the scope).
However, like many people say, measurement is always not the first priority.
(This argument is often used by lower grade/cheaper parts sellers, as they claim
their sound is #1). But for me, and most other engineers I know, measurement and
specifications is still the #1 priority. And to have both [good] sound and
specs, the transformer will usually cost significantly more. But I have to say,
the Classic MK2 is already a very best voice to beat.
The power amp resides in the middle of the chain
so it sees what is handed down to it and feeds whatever speaker you might have.
At one point, thinking I had not burned in the amplifier sufficiently, I
re-installed my Musical Design preamp and did some critical listening with the
2A3-S. Totally catching me off-guard, the transparency seemed to pick up a
notch, the dynamics kicked in and there was more music in the mid-treble. The
downside of this combination was an increase in grain, more vagueness in the
soundstage and less tonal coloration. Because of the different volume controls
of the two preamplifiers it was impossible for me to match levels but the
differences were obvious enough to make the point that what goes in will have a
significant impact on the output of the power amp. The 2A3-S deserves a very
high quality preamplifier and source; it was not out-classed by the Coincident
Statement Line Stage.
Time For A Nightcap
Carl had some pertinent comments on the Mundorf EVO caps. He wrote:
The Mundorf EVO Silver Gold Oil Caps to my surprise didn't add any greasiness or slowness to the sound at all like some oil caps do (or in short, the cap's personality override everything else). [With] some oil caps I also hear a bigger treble rolled off, which could be a problem to classical music listener, because the pitch of force striking the piano key will be gone and now the violin high note passage [will] sound more like a viola high note. Some micro details in the high frequency can also be gone. Anyway, it did not happen with the [Mundorf] EVO S/G/O cap and it actually added a grand kind of sweet coating on it... some of the micro details actually come out more clearly.
The Last Dance