August 17, 2021 8 min read
he story of the Ampsandsound Zion Monos (website) is the story of the best amplifiers I’ve ever had in my system. Full stop. Go back and read that twice. If It seems like I’m giving away the punchline before I’ve told the story, it only gets better from here, because this is also a story about one of the most beloved hi-fi amps ever made—the Harman Kardon Citation V.
The little brother to the Citation II, which was released in 1959, the Citation V followed Harman Kardon designer Stewart Hegeman’s philosophy of massive bandwidth and linearity. The original output transformers on the Citation II, built by Freed, are exceptional feats of engineering and boasted a bandwidth of 230 kHz full power. This is a pretty astonishing number even by the standards of today’s solid state amplifiers.
The input stage was, somewhat strangely, 12BY7 pentode input tubes—likely selected for their wide bandwidth—followed by triode 7581s, or more commonly these days, 6L6GC. The input stage is a simplified version of the earlier Citation II, doing away with the complex phase splitter and multiple nested stages, but keeping the fairly high feedback, which helps the amp achieve that remarkable output bandwidth.
For anyone who has heard these amplifiers, they do not conform to typical expectations of 1960’s tube amplifiers. While the imaging and soundstage are remarkably textured and organic, they are also exceptionally resolving, surprisingly linear and in some setups can even sound a bit dry and hyper-resolving. Bass far exceeds what one might expect from the conservative 60W rating, and the amplifier has earned a deserved reputation as a bit of a vintage collectors item.
There are some downsides however. The Citation II doesn’t have an easy way to bias the tubes, and the 7581 tubes are becoming increasingly rare, meaning 6L6GC tubes often get substituted. A bias pot mod has become popular, followed by power supply modifications such as a choke, more capacitance and updated resistor boards.
In enters ampsandsounds’ Justin Weber, whose gear I’ve long liked but recently come to appreciate more for being one of the only hi-fi manufacturers channeling those classic vintage sounds we seldom enjoy any more. There are some surprising and deep secrets in these classic designs which, to my ears, very few if any modern designs can replicate. And I don’t just mean minimal feedback SET amps.
In conversions with Justin he expressed to me that he set out first not to make a new flagship monoblock amplifier, but instead to build a pair of amps for his personal use. Full turret board construction 12 gauge cold rolled steel, and an output transformer which could live up to the magic of the old Freed iron were all on order, and as the amp morphed into a new product—as these things often do in hi-fi once a customer gets wind of a special creation—some tweaks to the original design were in order.
The product page has an excellent overview of the design:
“This is a Classic design, decidedly prosaic. The Ampsandsound Zions are built in a way few modern amplifiers employ. This is not due to intrinsic inferiority, but rather it is impossible to rush and is incredibly expensive to produce. Some of the most familiar tube amps ever produced utilize this method, including; McIntosh, HK, Leek, Quad, & Western Electric. These amplifiers demand to be played and built to last a lifetime.”
Point-to-point wiring, the aforementioned turret boarding, and an ampsandsound addition of tube rectification, make this a bit more similar to something like a modified and repaired Citation V than the original amplifier, however the Ampsandsound Zion Monos do include the original DC balance adjuster.
As Justin lives just a little over an hour away from me in Southern California, I opted to go pick up the amps, and was treated to a wonderful listening session in his home listening room before he helped me lug these hefty works of art into my car. I’m quite glad to have had this help too, as even with the very nice flight cases with wheels—honestly every piece of audio gear should come in casing like this—they still weighed somewhere in the realm of 60 lbs or more, and were quite unwieldy.
Setting them up was a relatively straightforward affair, simply a matter of lugging the extremely heavy amps into position, inserting tubes, and remembering to turn the amps on last and off first. Justin kindly included extensive bench results indicating the units were tested and working and that both amps were outputting just shy of forty watts.
Also included were instructions on how to bias the amplifier, which was no mean feat as a signal generator and scope are recommended. Owning these beasts is not for the technically averse. My one complaint about this unit revolves around this: there isn’t really any concessions made for convenience in the design. If you don’t know what a DC balance control is, how to operate a scope and bias tubes, signal generation, etc. then the Zion Monos will require you have a tech on hand who can do such things.
Additionally I found one quirk with the units, which was that switching them on and off rapidly would pretty reliably blow the rectifier tube. If you switch off the units, you should give the amps about ten minutes to bleed off any excess current before turning them back on. As I said, no concessions have been made for modern audiophiles used to sophisticated autobiasing, handholding, auto-mute switches and the like.
Fit and finish is spectacular and old school. The chassis is a gorgeous painted black steel that feels like armor plating for a tank. Both XLR and RCA inputs are provided, though I preferred the RCA slightly. Justin mentioned that the XLR inputs are using transformers, and while very good, they do scrub a little high end off. Differences are minor and both will serve you well, as will the choice of several impedance taps. 8 ohm seemed happiest with my Proac D30RS speakers, so that was what I generally stuck with, though I did try all the taps.
Oh my lord. Living in LA and working in the audio industry, I have the pleasure of hearing both expensive studios and rarefied and exotic pieces of audio history. Some of the experiences are disappointing, others astonishing, and more still sound very good but in unusual or odd ways. What the very best gear accomplishes is something that very few pieces of hi-fi manage, or even come close to, and that is a total involvement in the music. Old 1940s theatre systems, certain Altec amplifiers or Langevin equalizers from the 1960s, strange tube synthesizers from the 1930s, whatever it may be, the cream of the crop does something which rises above any ideas of frequency linearity, or dynamics or indeed any technical description of sound, and simply serves you a musical cocktail that leaves you totally addicted. I am rarely surprised, but when I hear gear that does this, it rekindles my love for the hobby.
To say that my jaw dropped when I first played music through the Ampsandsound Zion Monos would be an understatement. Running through an all triode system consisting of a ModWright PH9.0 phonostage, a custom triode Bendax 6900 tube linestage and the Zion Monos, vinyl was breathtaking. For the listening session I frankly couldn’t tell you anything about the frequency response or technicalities other than that they were astounding. I took me two or three sessions to really get a handle on these puppies—and I listen to sound for a living.
What is immediately apparent however is an unbelievably tactile and palpable sense of the auditory image. Gone is any sense of artificiality or in-harmonic specs in the soundstage, replaced by the densest, most pristine and most elaborately textured auditory image I’ve heard in my setup. I typically try not to wax poetic, but when I put the Zion Monos into my system, I became aware of a kind of pressure in the room, almost similar to the feeling of achieving the maximum bass pressure a room will handle before walls start rattling. Instead of bass pressure however, the Zion Monos presented an electric and harmonically charged presence that quite literally sent tingles down my spine, goosebumps up my arms and made my chest flutter as I engaged with music familiar and unfamiliar at meditatively deep levels.
What makes this presentation even more special is that the bass was tight, titanic and lower than any amp I’ve had in this system, yes that includes several hundred watt solid state amps. I never heard a single inch of excess midbass hump, softness or bloat, and yet even at high volumes, my Proacs seemed to puff up their chests, stand tall and fill my converted downtown loft with subterranean information like 8-foot tall dual 15-inch behemoths.
The top end was likewise simply perfect. Unlike many amps where tonal or harmonic juiciness comes at the cost of aberrations or colorations in frequency or dynamics, the Zion Monos were also amongst the cleanest, quietest and most precisely detailed speakers I’ve heard. Delineation between quiet and loud, and that special tube quality of adapting to the relative micro-dynamic plankton of each recording were all present, yet I could detect almost no audible coloration. Only several weeks in and during deep A/Bing with several other amplifiers I know quite well did I detect perhaps a slight extra density and richness in the lower midrange. Rather than a major frequency response hump, this was not distracting and only enhanced the meaty, super tactile presentation, and I can’t imagine it being a problem in system matching unless you have a severely tubby room response.
I don’t often compare the exotic gear I hear in LA homes and studios to anything in the hi-fi world, but here was an amplifier collecting and channeling a significant degree of the magic of that old gear, while retaining and surpassing the technical capabilities of any hifi gear I had in my possession. These Ampsandsound Zion Monos didn’t sound like Citation Vs at all—they sounded better. Much better.
When it comes to dynamic capability the apparently modest 39 watts also shocked me. I was hearing both vinyl and digital explode out of the speakers like canon blasts, never drawing my attention to specific frequency ranges or instruments, simply immersing me in the music and arranging every iota of musical information around me like some kind of planetarium star chart, infinitely well defined and inescapably immersive well beyond the visual periphery. I pretty much failed at making any listening notes because I zoned out every time I turned these amps on.
As for soundstaging, the entire audio image became almost comically disconnected from the speakers. Hard panned left and right elements were so wide as to almost seem as if sound was emanating from the walls, and images became so transparent I could walk around the room, well away from the sweet spot and still get a strong sense of the auditory image without any collapse even close to 90 degrees off axis. Woah. That’s a new trick.
If it seems like I’m raving a bit, it’s because I am. The Ampsandsound Zion Monos are quite simply the best amplifiers I have ever heard in my system, and quite possibly the best hi-fi amplifiers I have ever heard. Not counting museum pieces and raritanium of course, because unlike those, you can actually purchase these amplifiers for $16,000/pr.
Now, I have to say the lack of convenience features is a big hurdle, even for someone relatively comfortable with tube amps, biasing and even using a scope to do balance adjustments. Being careful about pops and cool-down time was likewise an annoyance. But if you those things don’t bother you, and frankly they aren’t terribly big cons in my book, I have a hard time actually naming an amplifier which I feel is in the same league as these. If you’re looking for the very best, and you have speakers which will work with these—i.e. not sub 2 ohm beasts requiring massive current—I cannot think of another amplifier that’s in the same league as the Ampsandsound Zion monos. Given modestly efficient speakers, these have my unconditional recommendation, and I feel musically poorer since they’ve left my system.