POSITIVE FEEDBACK ONLINE - ISSUE 37
The Tube MKII preamplifier
as reviewed by Ryan Coleman
If there are four ubiquitous words that are to describe the ideal sonic impact of a preamp, they'd be "straight wire with gain." I cannot tell you how many times I've read that phrase. But truly, all preamps are just that—the kicker is that, much as wires sound different (the reason we don't just use $3 interconnects), all preamps do as well, and ultimately their sonic influence can make or break a system. But why is this the case? A preamp's job seems simple enough: provide source selection capabilities, and amplify the incoming signal, right? Well, let me offer an analogy. Have you ever tried hitting a baseball? That seems simple too: see ball, swing bat, hit ball. Piece of cake! Well, not quite…hitting a baseball is the hardest task in professional sports, and it strikes me that preamplifiers have a far more difficult task than we assign to them (though admittedly, loudspeakers have the toughest job).
I realize this, as when listening to a statement preamp like the Einstein The Tube MKII, one realizes how most preamps commit a predictable series of errors, in dynamic contrasts, harmonic complexity, and tonal accuracy. It is only listening to the Einstein that I can identify and describe these errors by their absence with this unit in the system.
I was originally turned onto the Einstein preamp as a serious piece by some local audiophiles who found it (as I did) superior to the legendary CTC Builders' Blowtorch preamplifier. I reviewed (and purchased) the original version of the Einstein preamplifier for Dagogo a few years back (found at http://www.dagogo.com/EinsteinTheTube.html), and refer you there for background information on design, ergonomics, and general impressions. Indeed, I stand by every word of the original review, and if you've not read it, I'd encourage you to do so before continuing with this piece.
In rereading the original review, I think it worthwhile to elaborate upon a point that we audiophiles struggle against in what is ultimately a losing battle: dynamics. Lets ignore for a moment how poorly mastered most music is, where ham-fisted engineers compress dynamic contrasts into a hot, flat, lifeless recording where a drum attack conveys no further dynamic impact than a guitar strum. Instead, let's look at the home audio system: source gear, preamp, amp and two speakers. Now, simple physics dictate that there is no freaking way that a home system will ever bring the dynamics of a live band into the home. A live band/orchestra/ensemble takes up the whole stage of the venue, and we want that same scale replicated by some puny speakers? Its not happening, folks. Unless you're getting speakers as big as a Mack truck in a mongo listening room, you just don't have the size necessary to convey that same dynamic scale.
Beyond the undersized speakers we live with in real-world listening rooms, we all known that a suboptimal speaker and amplifier pairing will not reproduce dynamics properly; this occurs whenever amps are underpowered for the speaker's sensitivity and impedance. This is well known. What is far more insidious is the fact that preamps routinely rob music of its dynamics. My experience with various passive preamps confirms this fact; despite short interconnect runs and impedance matching components, passive preamps just don't have any cojones. So, the corollary of this thinking is that active preamps are required for proper dynamic reproduction, and if we're talking active, we're effectively stating that the power supply is the determinant of dynamic reproduction within any amplifying design. Hallelujah! I've been preaching this fact for years: you listen to your power supplies. And the Einstein Tube preamp, with dual transformers running in Class A, strikes me as having one of the most elaborate and over-engineered power supplies I've ever seen in a preamp. As a result, it should not be surprising that the Einstein has, hands down, the most forceful, impactful dynamic range of any preamp that's crossed my path. Assuming the rest of your rig is up to it, the Einstein MKII preamp can be downright scary in its ability to let dynamic music explode into the room. Live music is visceral, and the Einstein Tube MKII is, if nothing else, visceral. Conga drums, pianos, kick drums have jump, drive and verve, where lesser preamps simply have the sonic details. No, the battle to reproduce lifelike dynamics in the home cannot be won, but losing never felt better.
Rare as they are, other highly dynamic components are out there. However, a common bias against ‘high-impact' stereo is a tonal whitewash, where pianos are a bit too threadbare, a cymbal loses its shimmery decay, and Sinatra sings a bit more in the throat than the chest. And that's generally what I've heard with other gear that does justice to music's dynamic nature, whether it be from high sensitivity horns or mega-watt solid-state amps; while they deliver the dynamic envelope, they fail in fully fleshing out the tonal palette. The devil is in the details, and it's the micro-details, fleshed out far better in tubes than in semiconductors, that fully develop that tonal palette I wrote of. Now, tube amps don't have this tonal limitation, but as there's no free lunch, power and drive are lacking compared to their solid-state brethren. (In system building, I'd generally recommend a tube preamp delivering the harmonic complexity with a solid-state amp for the linear drive and dynamic gestalt is the best way to balance sound.) The Einstein preamp is of course tube based, and it always displays a midrange and treble with all the low level harmonic complexity that gets lost in all but the best amplifying devices made. This is one of the areas that I could easily perceive the differences of the MKII preamp vs. the original Tube; thanks to the elaborate vibration-resistant input tube sub-chassis (which I'll discuss further in a moment), the upper registers are delivered with even more crystalline shimmer. Cymbals have their last dying gasp of brassy decay, pianos tinkle like water, and Sinatra bellows at his highest powers, singing with the voice of God.
At this juncture, I must give my regards to the tube rollers in the audience. For those of you (like me) who think that tube rolling is a fun and worthwhile effort in the pursuit of your system's optimal performance, the Einstein MKII is going to be a hoot. The Einstein uses 18 of the ubiquitous 6922 tube, eight for the output stage and 10 for the input stage (only two are active and used at a time; one for each channel, two for each of the five source selections). Rolling the input stage tubes from the Jan 6922s to some 1970 Mullards helped me reduce the mid-bass wooliness I was getting in my rig (common in my speakers) while providing a bit more linearity in the top octaves (rather than the tipped up balance Wilsons are known for). For audiophiles with state-of-the-art systems, tube rolling can change the entire voicing of the rig. What is right for my rig might not be right for yours, but with the infinite varieties of the 6922, you can eventually find the tube that's best for your system, keeping the Einstein at the heart of it.
During tube rolling, I noticed the most obvious physical change between the original Tube and the MKII unit. All of the tubes in the input stage are suspended with a spring-based vibration control system, rather than simply being screwed into the chassis. When rolling tubes, the tube catchers bob up and down as you push and pull on the tube (to roll tubes, simply hold an adjacent tube stationary and voila!). This is likely the reason why the MKII unit is clearly superior to the original version of this preamp with regards to one element that eludes so many systems and components: focus.
I think back to my first high-end audio experience, at a dealer now defunct who had Wilson Watt Puppy 6s with Audio Research gear, which meant absolutely nothing to the uninitiated such as I at the time. I stumbled in on a lark, and didn't even know how to listen properly, but I do remember that when I turned my back on the system (again, I didn't know how to listen), I got the distinct impression that there was a clarinet player piping away in the room; a pulsing, physical body was right behind me, clicking away at the valves of the clarinet while sucking in air and thrusting it through that woodwind. And I thought "my God, I never knew a stereo could do that." That was my introduction to focus, which has since been revised upwards as my experiences have grown. And that's what the Einstein Tube MKII preamp in the system does: it gives a new definition of focus.
To elaborate, focus is the difference between a sharp photo and one done by a professional with a highly focused lens on a 35mm camera. Focus is the difference between a 1080 LCD with HDTV and an analog television set. Focus is the difference between hearing a guitar being strum and hearing the strumming along with the individual strings; it's the difference between rollicking bass and a musician picking the specific notes on an electric bass guitar; it's the difference between a soundstage and space between and behind the performers. And in my experience, the presence or absence of these sonic playback parameters that I define focus with goes hand in hand with the presence or absence of our mutual enemy, dear reader, and that enemy is micro-vibration.
Cheap stereos sound cheap because they flex and bend constantly; if they didn't, they wouldn't be cheap any longer. That's what defined my first audio experience; I finally heard a system that could focus because it didn't flex and vibrate. As time passed I took ownership of quality high-end gear that did resist vibration and was duly rewarded with great tunes; but as an audiophile intent to push the envelope in this hobby, I found focus to be like the ocean: you can go 10 feet deep, or a mile deep…and the deeper you go, the more you see that you never would have imagined on the surface.
I like reading Art Dudley, and he's one of the only writers in a major print rag that I read every word, but he's obviously not pushing the edge of the art if he's not trying to remove every last vibration from his system. Some audiophiles give short shrift to tweaks like footers and stands as overpriced hoopla, but these are audiophiles whose systems are not of sufficient quality (or are poorly optimized) to hear the obvious sonic differences of vibration control systems. In audio playback, everything matters. Vibration control in line level gear is no different than it is in loudspeakers (where staging and detail is dependent on an uber-stiff loudspeaker chassis that gives the drivers an inert reference for their movements). Those low level signals are delicate, people! Whether in the speakers, source, the preamp, or your cables, take care to keep them isolated, and you shall be rewarded. If you get good gear, position your speakers properly, and address bass nodes and reflection points in your room, you will have a good system, but until you isolate the signal from vibrations, you will not have the lowest level information that defines focus. Doing so can and will unleash a level of detail and clarity that will amaze you. I've spoken of this in my follow-up review of the EMM Labs CDSA player, and I will say that the new version of the Einstein preamp is a clear improvement over the original thanks to the vibration control system on the input tubes. Simply, it is all there. Everything the source retrieves, the Einstein delivers with force and clarity.
I'm not inclined to say this is a world-class, paradigm-shifting preamp that must be heard to be appreciated; after all, I said that in my original review, and I'd hate to repeat myself (despite the fact that I am just as enthusiastic about it two years later). What I would like to impress upon you, dear reader, is that the MKII version of The Tube from Einstein takes a state-of-the-art design and improves it in ways that are clearly audible for the enthusiasts whose systems justify spending big bucks for a linestage. The isolation of the linestage tubes greatly improves the overall focus of the unit, manifesting itself as a more clearly defined soundstage with 3-dimensional depth and body along with better articulation in bass transients and reproduction of microdetail within the midrange and treble.
But rather than getting mired in the details of the improvement between the original Tube and the MKII version, let me again impress this matter on those considering a reference preamp: you will not find a linestage that can deliver the dynamics of live music into the home better than the Einstein The Tube MKII preamp, and without this level of dynamics, you will never be able to approach the illusion of live music in the home. Now, couple the visceral performance I've described with an impossibly small noise floor, fully balanced operation, frequency extension, a see-through soundstage and the ability to swap tubes (the 6922s) in order to sculpt the tone of your system to your taste, and you've a preamp that can adapt to any reference system you currently have (or may build in the future), while taking it to levels that were previously unknown. I dare say that "system matching" will never be an issue when the Einstein preamp is at its heart.
At $17k, this preamp is not for everyone. But if you've the resources, an audition is mandatory before purchasing anything else. I offer this unit my highest recommendation. Ryan Coleman
The Tube MKII preamplifier
Questions to Volker Bohlmeier, President of Einstein Audio.
How long has Einstein Audio been in business? How many employees does it have?
Einstein Audio got started in the late eighties and there were only three people in the company at that time. Now there are 10 people working for us and we will continue to expand step by step.
I understand you've been expanding your operations as of late?
Yes, we expanded our operation quite a bit lately. We've always been able to sell all the products we manufactured in Germany, so we were never in a hurry to explore additional markets for export. But the export market is growing and we've had to as well.
I was obviously fond enough of the original Tube to have purchased it as my reference piece, but evidently you found room for improvements. What prompted this?
I think there is always room for improvements with every item. Our philosophy is that we constantly improve our products when possible. Referring to The Tube, we got some nice ideas for isolating low level signals from vibrations thanks to our efforts on our newly designed CD Player The Source.
What changes have been made in the MKII version of The Tube preamp vs. the original?
One thing was to isolate vibration and resonances from the 1st stage of our preamp (the 1st stage is the input stage as well as the differential stage). As we saw in The Source, we found that at the 1st stage micro-vibrations and low frequency resonances damage low level information, and this low level information is critically important for the imaging, the focus, the detail retrieval and the overall musical presentation. So we came up with the idea to isolate these vibrations with a suspended chassis. (Incidentally, this is very common on early turntable designs.)
Because of this mechanical operation, we had to increase the quality of the power supply, as well as shorten the signal path to the second amplifier stage.
Electrically The Tube MKII is even more `dead quiet` than the previous one.
Can the original unit be upgraded to MKII status?
It can be done, but economically this doesn't make any sense at all. Since the changes to be made are very time consuming it will be too expensive. It would make more sense for owners of the original Tube to simply spend the money on an isolation system beneath their preamps; it's the same goal in both—isolating the signal from micro-vibrations.
Volume controls are routinely responsible for signal tracking errors, image wandering, and sonic degradation—as they say, there is no perfect part. But in both the previous and the new MKII version of your Tube preamp, the volume control is outside of the signal path, which from a purist standpoint is the best possible configuration. How did you achieve this?
Our potentiometer acts as a shunt and reduces the impedance with lower volume settings.
Signal to noise remains about the same (around 95dB) even on very low output levels.
What other design features in The Tube are you most proud of?
I think there are quite a lot interesting ideas in the design of The Tube.
There is no relay, switch or semiconductor in the input circuit of the tube. To change the input, we switch the filaments of the tube itself.
The two differential input stages generate a truly balanced output signal, independent of the input signal.
The high current, low impedance output stage is capable of driving very low impedance loads (down to 100 ohms).
Extremely wide bandwidth (around 2Hz to 300kHz) results in absolutely phase linearity, but this is accomplished with very low distortion.
It seems Einstein electronics strongly rely on balanced connections as opposed to the more common RCAs, why is this?
Simple: Signal to Noise is much better with a balanced design.
The dual transformers run hot for a preamp; I gather they are biased in class A. Why did you use 2 transformers instead of using just one, and why would one choose class A instead of class AB (which runs cooler)?
We use a class A circuit, because it has much better linearity; as an added benefit, the output impedance is much lower, making amplifier compatibility easier.
We use two transformers to realize two completely independent channels, which allow us to optimize our star grounding arrangement, thus providing the best imaging and lowest noise floor possible. A stereo's preamp should be the center of a stereo's ground, in order to overcome any hum and noise problems. Our source components are designed to meet this design idea.
What do you consider the biggest challenges in the design of high performance audio electronics? Achieving a low noise floor? Getting realistic dynamics? Tonal accuracy? Detail retrieval? Etc.
We have to get it all. Music is so complex, that you can't miss any of these challenges, or you change your stereo system like your socks.
Why do you think most audiophiles fail in their goal to reproduce the live experience in their listening rooms?
Most audiophiles believe that cables, sound bowls, and other accessories made a bad system sound good. That is not real. If the basis (room, amplification, and source) isn't good enough, then the system will never be right despite uses the most expensive cables and the most expensive accessories.
To get an excellent musical system you have to start from the basis, the roots; only after that should one try to get the finest details with the help of cables or accessories.
What designers and products do you admire?
Peter Walker and his incredible design of the Quad ESL 63 Electrostatic speaker.
Simon York and his excellent S7 turntable.
NAD`s first 3020 integrated amplifier design ages ago.
The idea behind the Decca pick-up.
Well executed OTL tube amplifiers.
The Klein and Hummel Tuner FM2002.
Your products seem to exist in the "cost no object" territory. Do you design and build to achieve a price point, or are all your electronics built without regard to cost?
We will never design a product to achieve a certain price point. This will always limit your design. If someone has the brains to create an excellent product, they should do it and not be constrained by price points.
However, our electronics are not built without regard to cost; we could have a thicker front panel and we can have massive gold knobs, but is the world waiting for these features on our electronics?