The Authoritative and Potent Violectric V281 Headphone Amplifier Page 2

Violectric_V281_Photo_TwoV281onDesk

When using a flagship amp like the V281, I see no reason to mess around. I go straight to my best gear so there can be no excuses, and nothing to hold back even the smallest bit of performance. The system includes an Equitech power conditioner, an Aurender X100L music server, the Audiophilleo 1 with PurePower, and a Resonessence Labs Invicta Mirus DAC. This setup is about as revealing as they come, giving the amp an absolutely pristine signal to work with. I used a wide variety of headphones including Sennheiser HD800, HiFiMAN HE-6, AKG K812, Audeze LCD-3, beyerdynamic T1, and even some custom in-ear monitors like the Noble Kaiser 10 and EarWerkz Legend R. Suffice to say I covered all my bases for every type of headphone imaginable.

How does the V281 handle such a broad variety of loads? In a word: effortlessly. The first thing that struck me was how truly effortless the amp sounded regardless of the headphone being used. I started with the notoriously temperamental HD800—a higher impedance headphone with a reputation for being fickle with amplifier matches. Make the wrong call and the HD800 is sure to get on your nerves, its technical brilliance overshadowed by a bright top end and less than ideal bass impact. Using a balanced cable with 4-pin XLR termination I could tap the full measure of Violectric's design, and what I heard was breathtaking. Or, to use less hyperbole, it simply sounded "correct", in every sense of the word.

I cued up Gerry Mulligan and Chet Baker playing their Live at Carnegie Hall which I often use to get a sense of dynamic ease. The CD version of this album is pretty good but I use a copy ripped from the 1975 vinyl release which is comparatively unfettered—more dynamic, with a sense of transient flow not present on any of the CD versions I've heard. I admit I have yet to track down the limited edition gold plated MasterSound release from 1995, but I'm not holding my breath on that one. In any case, the vinyl rip has explosive dynamics at times, and the V281 makes the HD800 jump like I've rarely heard. I expect this sort of thing from an LCD-3 or HE-6 but HD800 can often sound more restrained. Not so in this system. The funny thing is, this album is musically on the smoother side; this is no Holst The Planets in terms of sweeping dynamic bombast. And yet, the V281/HD800 combo made the hair on my neck stand up when it came to approximating a true live performance, with all the authority that entails. Brightness? Thin low end? Nope, not here. It struck me that the HD800 has been on the market for over 6 years now, and has yet to be definitively surpassed or even matched in the case of some competitors. I can sympathize with folks who don't love it but I also feel they perhaps need to hear what the Sennheiser is capable of when really driven to the limit. V281 does just that.

Switching gears, I grabbed my HiFiMAN HE-6 (again with balanced cable) and put on Felix Hell's Organ Sensation. A product of Prof Johnson by way of Reference Recordings, this is a killer release no matter which version you grab. In my case I went all the way to the top—the 24-bit/176.4kHz HRx release, because...why not? That said, the CD quality version streamed from Tidal is excellent in its own right. Young Hell, a prodigy in every sense of the word, displays his technical mastery in what is truly full range demo material. Very few real instruments dig down to a solid 20Hz (or below) which means we typically only get that type of deep sub-bass impact from artificial sources. Now, I do enjoy electronic stuff from Benga, Skream, and Pendulum, or old school bass music like DJ Magic Mike and Bass Mekanik, but it's refreshing to hear such massive rumble from a real life instrument. Not to mention the recording quality is in a higher league as would be expected from anything in the Reference Recordings catalog. The V281 drives the difficult HE-6 with pants-flapping aplomb, making this a highlight of my listening for the week. Prelude and Fugue on B-A-C-H: Prelude hits like a young Mike Tyson on this setup. The only thing missing is that visceral full-body subwoofer experience which sadly remains out of reach for headphone listening...but the V281/HE-6 combo does so well that my brain almost fills in the blanks.

The difficult HE-6, when not fed enough juice, tends to underwhelm. It remains decent but nothing special, and honestly I prefer the more affordable HE-500 under those circumstances. Running HE-6 from a powerful amp like Violectric's own V200 is where things start to change. The headphone begins to "wake up" and show its true abilities—bass slam solidifies which is a lot of fun, but more importantly the mid to high transition becomes more evenly balanced. Without proper amplification I find the somewhat bright HE-6 top end to overshadow the midrange. The V200 helps level things out but the V281 in balanced mode goes a step farther, showing HE-6 as a truly world class headphone. V281 clamps down on those highs with vice-like authority, letting clarity shine through while maintaining control and focus. And that midrange, so often buried, really comes out to play, showing a sense of swiftness and versatility rarely matched by other headphones. I dare say this is the best I've heard HiFiMAN's stubborn flagship. Other powerhouse amps I've tried (including speaker amps) have done a very good job but the V281 takes top honors in my experience. Keep in mind, it's not purely a numbers game. The Schiit Lyr for example is very potent but doesn't come anywhere near this level. It's great for what it is but just can't match a Bryston BHA-1 or Schiit Mjolnir, much less the V281. If raw power alone was the criteria we'd all be running the HE-6 from speaker amps. I've done so myself and know a few people who swear by it. All I can say is, I have here a few rather nice amps here at the moment including an Anthem A2, a BAT VK-220, and a pair of Merrill Audio Thor monoblocks. Each of these amps is a powerhouse, sounding great with the HE-6. Yet none do anything amazing that I don't already get with the V281. Color me impressed.

Moving on once more, I settled on the LCD-3 Fazor and prepared to be underwhelmed. I've been running the big Audeze from a monster setup consisting of two Questyle CMA800R amplifiers in monoblock mode. Surely the V281, as nice as it is, would not be able to compete. Or would it? Initial impressions showed the competition to be tight, but after more thorough listening I give the definite edge to Violectric. The monoblocks sounded quicker and more insightful for micro-detail fact finding missions. Soundstage may have possibly been a tad larger, though both options were exceedingly open sounding. Where the German model took the edge was what I'd like to call "authority". You want to hear the resonating body of Yo-Yo Ma's 2.5 million dollar Montagnana cello? How about the full-throated authority of singers from Johnny Cash to Leonard Cohen to Brad Roberts? What about the textured attack and decay of the various Taiko on the XRCD release Dancing with Drums? The V281 accentuated the "Audeze-ness" of the LCD-3, which in this case seems the only way to go. In comparison, the Questyle duo was more lit up, more snappy, but also lacking in comparative tonal richness. If forced to choose, I'd take the V281 most every time, unless the DAC in play was of the slower, darker variety. That might end up being too much of a good thing.

The V281 seemed unflappable in its ability to unravel complex material. Shostakovich, Ozric Tentacles, The Bad Plus, Animals as Leaders, Respighi, Meshuggah... whatever tricky, complex, downright difficult music I have in my collection, the V281 never faltered in presenting it about as clearly as I've heard. Soundstage? Massive, but believable. Imaging? Precise. Microdetail? Plentiful. And again, it never seemed to care what type of headphone was connected. Low impedance, low sensitivity planar magnetic? High impedance dynamic? Multi-armature in-ear monitor with wild impedance swings? Doesn't matter, V281 handled them all brilliantly. Another benefit: seemingly endless reserves of juice. When comparing to other amps at moderate volumes, the differences were often quite small. But with a twist of the volume knob I'd often hear the competition fall apart or take on some new characteristic—strident upper mids, flabby bass, etc, while the V281 maintained the same poise it had shown at low levels. This reminds me of the best electrostatic amps such as my KGSShv or the Blue Hawaii Special Edition—such overkill specs might not make sense until you hear what happens to lesser amps as the volume climbs.

Violectric_V281_Photo_Guts

VARIETY
One thing I enjoy about the AURALiC Taurus MKII is the fact that it gives a slightly different flavors—the 1/4" jack and the balanced output are configured differently and thus have their own character. It's almost like having two amps in one...almost. The same can be said of the Violectric flagship. Everything I've mentioned above applies to the XLR output. Using either of the two unbalanced outputs taps only half of the circuitry, which essentially means listening to a V220—not the full potential of the V281, but still nothing to sneeze at. Some of my headphones are hard-wired (Ultrasone Edition 12, Grado PS500) while others use a single-entry detachable cable (AKG K812 and K7XX) making balanced conversion a chore. For those models I use the single ended jack and am still plenty impressed with what I hear. It's a slightly darker, more laid back presentation, with a bit less treble energy than the balanced configuration. This could be good or bad depending on the headphone in question—but let me clarify, this is by no means a massive coloration. The V200 was never an overly warm, syrupy amp, but rather a generally neutral one with just a touch of warmth and a slightly smooth top end. V220 seems to follow accordingly. At times, depending on my mood, I'll run my HD800 with an XLR to 1/4" adapter to tap the single V220-style output just to help make edgy recordings more presentable. Then I'll switch back to balanced when I play a better recording and want the whole picture. It's great to have options.

In keeping with the truly universal nature I've been harping on, the V281 is excellent with IEMs—but only when certain conditions are met. First off, don't use the XLR output. The increased gain (6dB, or twice as loud) of balanced mode is simply too much for sensitive IEMs, resulting in noise-floor issues. Single-ended mode has potential to work very well but care is required. The V281 seems rather sensitive to things like ground loop issues, so make sure your setup is buttoned down if IEMs are your thing. Just know that the potential is there for this amp to be exceptional with a JH13, Noble K10, Westone ES5, etc. That huge volume knob is perfect for very fine control of levels. Set pregain for -12dB and you have quite a nice range to work with—far better than most other power-packed desktop amps I've experienced.

Let's talk options. The first thing to mention is the DAC—I had the USB version installed in my review loaner, which would add $240 to the price. It's an asynchronous 24-bit/192kHz capable USB DAC using the Tenor TE8802 USB chipset and a Texas Instruments PCM1798 for actual D/A duties. While the idea of an all-in-one DAC/headphone amp/preamp is certainly appealing, I'm not convinced the DAC is worth it for most people. It's a competent DAC which doesn't really commit any glaring offenses. But it's just not up to the level of performance we get from the headphone and preamp stages. Not that I can think of many $240 alternatives that would sound anywhere near this good, but I think most buyers of a $2k+ amplifier will likely have something nicer available. Which relegates the optional DAC card to backup status at best.

Next up, volume control. The base model comes with an Alps RK27 potentiometer which is a solid choice, commonly found on many nicer headphone amps. Nothing to complain about. The first upgrade adds $290 for a motorized version of that same pot. We get a reasonably nice remote control covering all the bases, meaning true preamp functionality for speaker listeners. That may very well be everything one could ever need.

Going one step further will cost you $580. This replaces the RK27 with a custom made 128-step relay-based unit, with .75dB intervals between each step. This one is also motorized and uses the same remote. Designer Fried Reim tells me this version "produces the best channel balance, step precision, absence of distortion, and minimized crosstalk." This is the option I chose for my own personal V281, which allowed me to handily compare with the motorized RK27 in my review loaner. Any differences to be heard? Nothing drastic, but after extensive back and forth I did hear an improvement in transparency and focus—especially at lower volumes with sensitive IEMs. At this high of a level I don't believe there are any major gains left to be had. A small improvement may sound trivial for the price, yet is more of a big deal than it might initially seem. I'll put it this way—I'm used to my electrostatic system using a KGSShv driving the Stax SR-007 or SR-4070. The "basic" V281 paired with LCD-3 or HE-6 seems like a step down from my Stax rig, while using the upgraded V281 feels closer to a sidestep. Again, absolutely nothing wrong with the stock volume solution but if you can swing the extra dough I really do recommend the upgrade.

COMPARISONS
The Luxman P-700u ($6,000) is a stunning amplifier. It's one of the few components to match or even exceed the V281 in craftsmanship, as it should for the price. The Luxman has a beautiful, sweet presentation which oozes charm—when the mood strikes, there's no other amp I'd rather use. That's the thing though, a significantly colored amp is fun at times but doesn't really make for a great all-around performer. The P-700u is a bit of a sonic lightweight. It emphasizes vocals and sounds really airy, but the rhythm and drive of the music seems lost much of the time. Which is just weird coming from such a beastly looking amp. I have to assume this is a deliberate voicing rather than a technical deficiency, but it doesn't work for me as a general purpose amp—I just can't justify the pricing for such a specialty product. Needless to say, I prefer the V281, even before considering any price discrepancies.

The Meridian Prime with matching PSU ($3,250) is another letdown for me. If this thing was $1,100 it might be worth considering given the small form factor and all-in-one DAC/amp functionality. But at three times that price? No thanks. The V281 outperforms the more expensive Prime at every turn. Deeper, more palpable impact, more convincing imaging, smoother, more refined upper mids.... and it never runs out of steam (as the Prime sometimes can with difficult planar magnetic designs). Removing the Meridian power supply restores parity to the cost, but also widens the performance divide that much more. Another easy victory for Violectric.

Ok, so I'm cherry picking expensive amps which I don't particularly care for. I could do this all day—Sennheiser HDVD800, Cavalli Liquid Fire, RSA Dark Star, Bakoon HPA-21... My point is to show that one can easily spend big money without any guarantee of corresponding top level performance. How about a more realistic comparison, with an amp I actually enjoy? An obvious alternative would be the AURALiC Taurus mkII ($1,899) which I raved about. It's a killer amp that drives anything you throw at it, and as mentioned earlier it offers differing flavors based on which headphone jack is used. I like it so much I gave it a spot on the Wall of Fame for solid-state amps. As good as the Taurus is, when I remove my reviewer hat and just listen for fun, I find myself using the V281 more often. I end up not wanting to analyze what I'm hearing at all, but rather just get lost in the music. That's a really good sign. The Taurus seems slightly more lit up, while the V281 is smoother, more dynamic, with a greater sense of musical ease. That said, I never feel that I'm missing any details when running V281 fully balanced. It's like the top end strikes an ideal balance between extension and control. If you asked me last year I would have said Taurus hit that balance perfectly and could not be improved upon. Then the Violectric came along and surpassed it. At $500 less the Taurus may well be the better bargain, though I'm not sure how much that will matter to someone shopping in this category.

Another obvious competitor is the SPL Phonitor 2—it's priced within a few hundred dollars of the big Violectric, and is made just across town...ok, it's more like a 6 hour drive, but close enough. The Phonitor 2 is, in my opinion, a big improvement over the original model. Both have tons of great sound adjustment features but I always felt the amp section of the original was severely lacking. Phonitor 2 is quite a bit better, enough to where I considered giving it a write up here. I decided against it after spending some time comparing it directly with the V281 and Taurus. As fun as the various sound tweaking options can be, as a pure amp I still don't quite find the Phonitor 2 competitive in this tier. It's good, but not great. I find it a little flat sounding, somewhat closed in and boxy, and lacking the massive authority of the other amps. It just couldn't keep my interest. Again, a very nice piece of equipment, and possibly the better choice depending on what one might be aiming for. For my particular needs, it's not something I could see myself using in the long term.

FINAL THOUGHTS
There really is no easy conclusion to be drawn here. I am obviously smitten by the Violectric V281 and find it very easy to recommend if one truly desires a top caliber headphone amp. I count it right up there with the very best in existence—HeadAmp GS-X mkII, some of the nicer Eddie Current models, and the discontinued ECP L-2. All of these are statement pieces which I consider far beyond the optimal price to performance ratio. Common sense would dictate we spend a lot less and still get a very good amp—several more affordable Violectric/Lake People models offer just that. However, at some point common sense goes out the window, and we just want the absolute best available. If that's your situation, the Violectric V281 deserves very serious consideration—and a spot on our Wall of Fame.

Ed Note: I'm requesting that John send me this amp so that I can include it in my upcoming round-up of high-end gear. The final determination of what amps end up on the Wall of Fame will occur after that series of articles.

RESOURCES
Violectric home page and V281 product page.
HeadFi discussion thread.

COMPANY INFO
LAKE PEOPLE electronic GmbH
Turmstrasse 7a
78467 Konstanz
Germany
+49(0)7531-73678
ARTICLE CONTENTS

COMMENTS
XVampireX's picture

Great review.

Any chance for an Audio-gd review by you or Tyll?

Innerfidelity has never done 1 review of an audio-gd product, seems fishy.

John Grandberg's picture

Not sure what to make of your "fishy" implication. What do you suspect is happening? But, to answer the accusation: I have a generally positive view of Audio GD. I reviewed their Reference 7 DAC at HeadFi some years back (when it was first released), and quite enjoyed it. I haven't spent any meaningful time with their newer gear.

Several issues have prevented me from seeking something to review. The main thing is how their lineup changes so rapidly. By the time I have a review unit shipped, do my listening, write it up, and wait for my spot in the publishing schedule, there's a good chance a new model will be out to replace the thing I reviewed. That's obviously not desirable from our standpoint - we want to keep our reviews relevant, and covering something that is no longer available is not the best approach. Not to mention their rapid pace has always made me somewhat skeptical... how much time is spent designing each one, when a replacement is always far behind? I know I'm not the only one to voice this objection.

Of lesser concern are build and reliability issues, language barriers, the massive size of the higher end models, the rather confusing naming conventions.... but the ever changing lineup is really the key issue.

That said, the Master series has proven to have staying power (for Audio GD products at least), so perhaps things are changing a bit. I will consider reviewing something from them if I spot one looking noteworthy.

cspirou's picture

Even more surprising to me is that there isn't a single review of a Schiit audio product. Considering how popular they are I would expect a write up of one of their amps or DACs somewhere. I see the Schiit ad all the time when I visit innerfidelity so maybe its a conflict of interest? Although I doubt that because I see an ad for Audeze as well and they have plenty of reviews.

John Grandberg's picture
We've actually given quite a bit of coverage to Schiit. Bifrost was favorably reviewed. "How Schiit happened" was highlighted. Modi and Magni were named "showstoppers" at T.H.E. Show 2013. Bifrost appeared in one of our Holiday Gift Guides. This in addition to plenty of other show coverage. And Tyll intends to cover Ragnarok soon enough. So no, we aren't avoiding them at all, I think most of us hold them in high esteem.
cspirou's picture

I missed the Bifrost review somehow but I found it. Although there is no review on their amps like you have done for the Violectric. I wasn't really insisting that you never mentioned Schiit but show reports aren't really reviews.

I look forward to the Ragnarok review though.

John Grandberg's picture

We've actually discussed this internally, and at one point had an amp review in the works (Mjolnir maybe?) but review loaners were hard to come by at the time, so it eventually fell by the wayside.

But you're right, we could do a better job on this, as Schiit deserves all the attention they get.

Impulse's picture

The one Schiit review on the site was also by Guttenberg... No offense to him, but I don't exactly come to Innerfidelity for his occasional guest articles (I can go to this CNet blog for that anyway).

Just saying, I come to InnerFidelity to read your reviews, Tyll's, joker's, etc. I'd welcome any and all reviews of more affordable amps/DACs tbh.

Bob Katz's picture

So, for low impedance cans, is it the headroom that makes it sound better? We know you're only using a fraction of that 5 watts. I ask facetiously because I believe in headroom having an effect. Why not match the output voltage of the Violetric with that of the $200 O2 amplifier (600 mw capable) and feed them both from the same external DAC. Then A/B compare the two. Inquiring minds want to know. In my upcoming review of mid-priced cans I intend to do the same with the Burson versus the O2, but I need to find a neutral killer amp (class D?) that won't blow my ears as well.

John Grandberg's picture

I tend to agree with you - headroom is important, probably more so than most people think. That may very well play into the subtle differences I hear between various well-designed amps.

Speaker designer Jim Salk once relayed to me a story about testing amplifiers. They set up both average power meters (RMS) and peak-reading meters and monitored power levels while playing music. While the RMS meters showed in the 5 to 8 watt range, the other meters showed peaks in the 200-250 watt range during instantaneous transients such as drum hits. So, while on average 5-8 watts was sufficient, the best possible performance was achieved with a far more powerful amplifier.

This seems to line up well with my subjective experience. A nice amp delivering doing even 100 mW can sound excellent most of the time. However, with some headphones and some music, a far more powerful amplifier pays dividends.

I'm glad we are are somewhat on the same page here. I look forward to reading the results of your upcoming experiment.

Bob Katz's picture

Dear John: The hardest part will be the "all things being equal" department. I could test my Burson and O2 at matched gain, but they obviously sound so different anyway how do I know the sonic improvement of the Burson is due to its headroom? So I would like to hear a more powerful but more neutral amp than the Burson. The highest peak to RMS ratio that I have ever measured is with some of my own audiophile recordings, and that could be as much as 24 dB.

I really should compare this in volts, but having the figures in my head, if the maximum wattage of the O2 is 0.650 and the Vioectric is 5 watts, that's a ratio of only 9 dB. OK, let's be more practical. Audeze LCD-X maximum power rating is 15 W for 200 ms. Let's not exceed that. It produces 103 dB with 1 mW. With a nominal RMS forte level of 83 dB, that would be 0.01 mW average power. 24 dB above that would be 2.5 watts. So 2.5 watts rating is probably enough to handle the most extreme transient peaks and not go deaf.

Bob Katz's picture

I didn't get my milliwatts and watts right. And there's no way to revise a post in this dang forum. I'll be back with the correct numbers after my afternoon run!

Bob Katz's picture

OK, so since the LCD-X are rated at 103 dB with 1 mW that's already the peak level you would ever want to drive within a few dB. So even a 1 mW amp has the headroom. The question that has to be asked is: Is headroom beyond, say, 1 watt in an amp at all meaningful when 1 watt is already 143 dB! So the numbers are saying enough is enough. It would be nice to make a controlled experiment and for me matching up the $200 O2 with the $2200 Violectric at matched voltages would be a very interesting test. As is my experience with subtle differences, most of them will dissolve when the loudness is matched and what's left will not be 10 times the improvement or whatever. But as usual, prices go up exponentially for the tiniest perceived improvement. That's the audiophile world.

zobel's picture

A $150.00 portable amp vs a $2300.00 stationary unit is a little like a Chevy vs a Lamborghini, but why not? I think they both will get you there, but the O2 will make music during the trip and at home, while the Lake People unit will only play for you while you sit in you stationary chair. I'm happy to see this comparison, and look forward to reading what you find out in the Burson vs O2. Choice of cans will be crucial there.

xnor's picture

If you use an O2 then keep in mind that high gain and high input levels can clip the signal regardless of volume control position.
Max gain = 7/Vsource, all in RMS, e.g. 3.5x with a CDP that outputs 2V.

Secondly, you need to level match with your headphones connected else you will ignore output impedance - load interaction.
If you want to do this properly then levels should be matched really carefully.

As killer amp, it's probably best to use a clean, low power (25W into 8 ohm should do), class AB speaker amp.

johthor's picture

This is a really great review. I have had the V800/V200 stack for about 6 months and really thought I was at a place where I no longer needed to upgrade. Now after reading this really superlative review I am not so sure about not needing to upgrade anymore. One thing I know for sure there will always be a Violectric component to my listening equipment

John Grandberg's picture

I spent several years enjoying the V800/V200 combo. It is EXCELLENT! The mere fact that something better exists, should not at all diminish your enjoyment of what you already have. You certainly don't NEED to update anything.

johthor's picture

Thank you for the response, John. I most certainly agree with you and will be quite happy with what I have until, and if, I decide to give the balanced route a try.

Bob Katz's picture

To repeat: I really want to test the contention that more power sounds better, at equal matched loudness. Can you at least do an informal (non-blind) test. Measure and match the voltages of the O2 (a very good sounding inexpensive amp) with the Violectric and let us all know what you think. Thanks!

John Grandberg's picture
I just boxed up the Violectric and will be shipping it over to Tyll as soon as he is back from vacation. I'm sure he would be interested in giving that a go.
Bob Katz's picture

I always test the losses of an amp under load. Most of the amps with low enough source impedances don't vary more than 0.1 dB under 20 ohm load versus high impedance. I'm not going to do the load test with the actual headphones. It'll be done with a load resistor. Too much money to lose if an accident happens.

My idea of a killer amp would not be Class AB. It would be fully Class A or possibly Class D.

xnor's picture

I guess that level-matching technique works okay if your dummy load matches the nominal impedance of your headphones.
A 0.1 dB deviation would be bad since your "profession is to make 0.1 dB decisions and to discern small differences". :P

I thought you referred to "killer" as in an amp with so much power that it could destroy any headphone in an instant, i.e. a power amp. :D
You know that AB does run in class A for typically up to a few watts, right? But sure, class A is fine as well.

I wouldn't choose a class D power amp due to output filter <-> headphone load interaction. These things are designed e.g. for 8 ohm loads, so you'd probably need to add such a resistor in parallel or measure the loaded frequency response to be sure.

Bob Katz's picture

Xnor, to answer both your comments: The problem with "reply" in this forum is that the forum software has no way to search for "unread posts" so it's easy to miss posts. So it's tempting to put a newest post at the bottom of the list. I know i'm going to miss a new post when replying within the stream because the software forces you to keep reading and re-reading every long thread.

Next, well, for me as is obvious by your :D sign is that "killer amp" would be one that sounds better than anything else. The hard part will be to determine why and make sure we're not fooling ourselves.

As far as output filter load interaction, you're talking about ancient Class D or those cheap chip amps. The best current-day Class D amps can deliver amazing power to most any load. Take a good look at the Hypex NCore spec sheets. Anyway, I had a long talk today with Bruno Putzeys, developer of the Hypex, and while there is no current-day Hypex headphone amp, maybe someday there will be, and it could become then the killer headphone amp if someone designs a discrete, 5 to 10 watt model. We shall see. Those little Class D chips do not excite me, but the discrete Hypex have changed the world.

However, Bruno recommended (and when Bruno talks, people listen) a small Class A amp for cans. I would concur. Basically there's no point in doing Class D for small signals. While it's true that Class AB amps operate in Class A for small signals, my experiences with Class A in loudspeakers have turned my head and I'll take Class A over AB for loudspeakers any day; their purity of tone just turns me on. And that was the case until Hypex and some competitors came along. Class D, however, has converted me and I have 5600 total watts of Class D power driving my 5.1 system. I no longer have any Krells or similar eating up my bankbook, electric bill or heating my Florida studio. And I don't miss the Krell now that the best of Class D has proved its worth.

Since pure Class A (when would it be "impure"? I guess if it turned into Class AB at some higher wattage) is reasonably simple to engineer for a small signal amplifier there's no reason to make a 5, 10 or 20 watt amp with any other topology, if you like Class A sound as much as I do. And it won't draw so much as to kill your kilowatt-hour budget.

cspirou's picture

If you are willing to build it I think a firstwatt F5 would be a good amp to try. Very low distortion and noise at 2x25w class A into 8 ohms which should translate into 6 watts at 32 ohms.

My other choice would be the NAD D3020. It is an ultra low distortion class D amp based on Hypex technology. Something built with a couple NC400 modules would be even better!

Bob Katz's picture

You just blew my mind. I have no idea why I didn't think of driving headphones directly from the speaker terminals of a D3020! I couldn't see the forest for the trees so many thanks for your suggestion. The NAD also includes a DAC for that price so it's a very special piece of kit.

I do wonder if the sensitive LCD-X will reveal any noise, however from the loudspeaker outputs. I can ask Bruno. The NAD price is amazingly good and it has that magic Hypex inside. If I could afford the price and the time I would build a Firstwatt. I've seen already-built Firstwatts going for about $2200 so someone should shoot that out against the Violectric! Again many thanks for that suggestion. And again the question arises whether sensitive headphones would pick up the noise of a Firstwatt as well. Have to settle that question before venturing into a 25 wpc amp, whether it's Class D or Class A.

Bob Katz's picture

Before buying that I would have to determine several things:

1) if it's ok to common the black terminals together or if I have to run the headphones balanced (floating common)
2) If the noise at the loudspeaker terminals is audible through the headphones. That would be a no-no
3) If the gain of the 3020 is so high that it would have to be modified inside.

Quite a few concerns! At least with the Pass amp you get a full schematic.

Bob Katz's picture

I just heard back from Bruno who said that very bad things could occur with a D3020 if making a common of the black terminals so I definitely would have to run my headphones without a common.

No answer yet on the gain structure of the 3020 and if I purchase it I would want to get a money back guarantee in case it's too noisy for sensitive phones.

The review and the NAD manual seem to imply that the built-in headphone jack of the D3020 is NOT derived from the class D amp and since it is an unbalanced jack that would be a clincher. A "dedicated headphone preamp" is described somewhere in a review or the manual.

Next I have to check with the wife to see if another $500 for "fun audio stuff" would even be permitted in our current financial times.

Bob Katz's picture

Similar question if using a first watt's speaker outputs: Would it blow up if using unbalanced headphones and common connecting the low speaker terminals?

cspirou's picture

At least for the F5 amp it shouldn't be an issue. According to the schematic the negative speaker terminal goes to ground and wouldn't really hurt the headphones. There are a couple fully balanced builds and you need more caution with those.

Looking up the Hypex amp modules it looks like the speaker outputs are not differential outputs and the negative terminal goes to ground as well. Although the NAD amp has a headphone jack which might be driven by the speaker outputs instead of a separate circuit.

xnor's picture

The best current-day Class D amps can deliver amazing power to most any load.

I didn't say otherwise. I said there can be output filter <-> load impedance interactions with some class D amps.
But with the Hypex designs this appears to be indeed of no concern.

The important thing to watch out for is noise in power amps. Even super-duper class A heaters will usually produce an audible noise floor if you directly drive headphones.

cspirou's picture

Just looked up the numbers for the amps I mentioned. F5 is around 100µV. The O2 has a noise level of about 3µV so the F5 is certainly much more noisy then headphone amp. Of course this is a major issue with driving IEMs and sensitive headphones. With high impedance headphones and planar magnetics the noise might not be an issue. There are some Firstwatt amps that have noise level from 30-50µV which is about the level of a tube amp and a bit more acceptable.

Assuming the D3020 is similar to other hypex amps, the noise should be about 30µV which is also acceptable. Note that the NAD amp has a headphone jack which is limited to about 6V RMS. I don't know if this is coupled with the speaker outputs or if it has a separate amp to drive the headphones. Either way, its worth checking to see.

Bob Katz's picture

Where did you get the 100 microvolt noise spec on the F5? These being unweighted figures probably make it tough to compare but on this page www.firstwatt.com/f5.html Nelson says it's got about 60 microvolts of noise. Don't know the bandwidth that's measured, but if it's wide band that's QUIET. The Audeze LCD-X produce 103 dB SPL with 1 mW/20 ohm, which is 0.1414 volts. 60 microvolts is 67.4 dB below that. So 103 -67 = 35 dB SPL. Which may or may not be audible in a quiet room, depending on the spectrum of the F5 noise.

cspirou's picture

I got it from the product page comparing all the amps.

http://www.firstwatt.com/prod.html

The page probably needs to be updated.

zobel's picture

Everyone knows that 1 dB is the smallest change in loudness humans can normally discern. Bob probably got his decimal point off again.
We should be kind though, he is aging like the rest of us, and forgets things, just like the rest of us, even, for example, what is bass, midrange, and treble in Hz. Forgiven.

xnor's picture

Nope, 1 dB level differences can be heard. Depending on the situation even fractions of a dB can be heard.

Fastl and Zwicker document 0.5 dB for random white noise at 70 dB SPL, or just 0.2 dB for a 1 kHz tone at 80 dB SPL.

There is a reason for the recommended 0.1 dB level matching in ABX tests.

Bob Katz's picture

This is the one and only time I will probably agree with Xnor. If you want to compare two amplifiers, you must match them to 0.1 dB or better. I guess the poster who mentioned the 1 dB never read my blog here :-)

xnor's picture

Oh and please use the reply button to reply.

zobel's picture

Has it ever been shown in blind tests that people, while listening to music can distinguish overall loudness level differences under 1dB? That is what I was wondering. No doubt for measurement purposes the 0.1dB matching accuracy is a good, probably necessary thing to achieve. I can't imagine a person having to make 0.1dB decisions by ear every day, with music or test signals. I think I would be a basket case, if I'm not already.

xnor's picture

Yes, smaller differences in volume than 1 dB have been detected.

But the claim about 0.1dB is indeed ridiculous.

Bob Katz's picture

Gilmore Dynalo looks like the bees knees and would give a run for the money of any commercial discrete Class A amp. If I build it from parts it would be a big money saver, but do I have the time and the energy it requires to find all the parts from a B.O.M. and then align it, match transistors and then debug it if it doesn't work first time. Egad.... So tempting.

The Twisted Pear Virtus is much closer to ready to go, buy the kit, power supply, add a case, 1/4" connector, input pot, input connectors and it should deliver a little more than a watt. The chip has a good reputation. In the end would it sound better than my discrete O2? Would it ever come up to the quality of a Dynalo? Would it prove anything about headroom?

Bob Katz's picture

I think the Dynalo build looks very serious if there's no kit. But the AMB M3 is cool because AMB provides such a nice helping hand, very nice step-by-step instructions. What a nice company, AMB! I calculate >2.5 wpc with the M3 maxed out with the 40 volt power supply into 20 ohms. And a lot cheaper than a Violectric. I can handle this! It's now on my list for rainy days in Florida.

xnor's picture

I wouldn't trust any of amb's numbers, see amb mini3 review.
Also see virtual grounds and 3 channel amps.

Bob Katz's picture

AMB measured their equipment using a Motu Firewire interface and made it clear that a lot of the noise and distortion that they found was latent in the interface. I use a Prism Lyra-2, which is about as close to the state of the art in converters as you can get, an order of magnitude better numbers and would be a better interface to measure with. AV guy did not find giant differences between the AMB "specs" and his own specs that could not be explained either by his use of different load resistors than they used, or the latent noise/distortion of his interface. Didn't he use an Audio Precision, after all?

As for the virtual ground thingy, AV guy may be right, but it's not as if the AMB M3 is suffering because of his insistence on that particular technology. It didn't get that reputation for that reason. One would have to build two otherwise identical M3's, with equivalent power supply quality, one with a bipolar and one with the virtual ground, and carefully A/B them in order to truly answer that question.

xnor's picture

amb's numbers are indeed very far off, even the simple math as discussed in his forum was off. This has nothing to do with the audio interface used.

Besides, the numbers are too good, not too bad. NwAv suspected that some of these tests were done completely unloaded - and he was right. Another user confirmed this by doing an unloaded test with similar result. I'm not sure if you can still find it, because these topics were closed or deleted and people silenced.

IIRC one of amb's defenses was that dynamic music is a far easier load than test signals, which of course doesn't explain the wrong math and fake "loaded" test results.

Anyway, I'm not saying the M3 is bad, just to be careful what this guy is selling.

woobanger's picture

I've been a happy use of the Auralic Taurus the past couple of years as my reference SS amp but have had the itch to replace with the V281 the past few months based on other reviews and a couple of short auditions at a local retailer.

My urge to upgrade had been in check recently simply due to being occupied with other things, but your review is reigniting the fire so to speak as I know you thought very highly of the Taurus and it seems you prefer the Violectric.

One other recent contender for the spot in my rack as the reference SS amp is the Moon Neo 430HA which I have heard excellent things about. I haven't had a chance to audition yet, but I'm a big fan of Sim Audio amplifiers and a sucker for power so I can only imagine it will be a positive experience.

Have you had a chance to hear the 430HA and if so, any thoughts in comparison to the Taurus or the V281?

John Grandberg's picture
Thank you for the relevant post. I don't have experience with the 430HA but Tyll has been enjoying it for a bit. I'll be shipping the V281 his way, so expect comparisons from him soon enough (along with several other high-end alternatives).
SonicSavourIF's picture

Nice review, poetic and all, but alas, non blind reviews, what can they tell you in the first place?

I really appreciate Bob's suggestion of doing a level matched blind comparision of the O2 versus the Violectric amp (maybe against the other amps, too?). Come on people, we know how much our brains can fool us. I'm really getting tired of reading long raving reviews on gear, when every time I am wondering, why doesn't any of those golden ear reviewers take the step of just comparing blindly?
If I saw the pricetags and the features and build quality of these super expensive amps, I would immediatelly be driven to think they can only sound better than an inexpensive amp like the O2. But do they really? Why is everybody so scared of really ansering that question.

Afterwards, you can still prefer the more expensive amps for ther fearure richness and build quality expensiveness and whatnot, so what do you acutally loose? Scientifically speaking, it is simply an interesting question to explore our perception, our ability to hear (or not to hear) a bit more thoroghly.

It would be so awesome to gain some reliable statistically significant blind test data with people that are really trained to listen to details (like Bob for example). It could be a huge fun to check the audability of amps that measure within a certain range of specs and for the fun of it, why not also include amps that don't? Just to see how much certain specs really matter?

cspirou's picture

Blind tests are a gigantic pain to run and I can live without those as far as regular reviewing goes, especially with anything involving headphones. Maybe specialized one-off articles where they get a bunch of reviewers in the same room but otherwise its a distraction.

What I would really like are measurements like we see with the headphone reviews. I understand that Tyll is getting close to getting his measurement setup up and running.

Bob Katz's picture

Actually I did not advocate a blind test for the amp comparison unless it was conducted and supervised by a psychoacoustician experienced in performing blind tests. There is no such thing as an informal blind test. I personally know two of the world's experts on blind testing and they can support that contention: Only the most formal and regulated blind tests under the BS.1116-3 protocol with proper training and proper choice of sources have any chance of succeeding on subtle variances.

With subtle differences such as we are likely to find and matched levels, a fully blind test on an ampifier is more than likely to come out statistically invalid and not satisfy anyone. We are a long ways from being able to make a funded (figure $100,000) blind test on the audibility of something even as simple as harmonic distortion.

So I'm fine with a level matched nonblind comparison. It's as good as it's going to get without taking years off and doing it blind.

xnor's picture

Repeating this doesn't make it right.

First of all: all audio engineers I know have done informal blind tests. You match the volume and then you either have a friend switch, or you use a switch box, or switch by software.

What you are talking about is a formal test that is conducted so rigorously, that it would be accepted for publication in a scientific journal. Nobody is asking for that here.

In previous comments I explained that just level matching and doing a couple of blinded back and forth switches is an experience that every reviewer should make - and I think such a procedure should be included in any comparative review.

Even a more formal test (something you could put into a review without being laughed at) is not that hard to do if you know what you're doing.

Saying it would take years is just a cheap excuse, because it most likely only takes a small fraction of the time you spend on sighted comparisons.

Bob Katz's picture

Xnor, sorry, you are wrong. An informal blind test is an improperly done blind test and is more than likely to produce null results. End of discussion. I can't waste my time talking about blind tests with non-experts.

xnor's picture

Then why do you keep talking about it? :D
Feel free to participate in blind testing discussions on hydrogenaudio -- let's see how much of an 'expert' you are..

Also saying "you are wrong" and then making a factually wrong statement doesn't help your anti-blind testing case.

If you don't do the level matching or switching or 'blinding' properly then you are more likely to produce false positive results.

And your sighted comparisons will overwhelmingly produce false positive results for exactly that reason - because it's not just a bad 'test', it's the negation of it.

zobel's picture

and years of reading totally subjective reviews of audio gear, I find myself in complete agreement with you, xnor, regarding the necessity and responsibility of reviewers to make at least one properly run informal blind test to compare what they are reviewing to at least part of the field of competition.
To me, the reviews with that information and some relevant measurements actually mean something and carry some weight, especially if the blind tests show no difference between products.

It is similar to blind taste testing food. In case of a draw, I would like to know the ingredients, and the breakdown of the measured nutritional factors, as well as who made it and where.

John Grandberg's picture

I'm truly sorry you are getting tired of reading this type of review. May I facetiously suggest you stick with only review sites which follow your preferred methodology? Your selection rapidly diminishes there, doesn't it?

You ask: What can reviews such as this tell you in the first place? I'll answer that I think it's pretty straight forward.... it tells you my experience with the device in question, how I enjoy it, what aspects could use improvement, how I feel it stacks up against others, etc. Seems to me this is directly representative of what a potential owner might want to know.

I'd love to get together with Bob and Tyll and some others, to answer the big questions in life. While we're at it, I'd love Tyll's full amp measurement procedure to be available right this second so we can begin to correlate (or at least try our best) what we hear with what we measure. Alas, neither of those are doable at present, so I'm left simply listening and reporting what I hear, using my modest experience in the hobby. Again, sorry if this doesn't satisfy, it is what it is.

SonicSavourIF's picture

Thanks for talking the time to answer, John.
You are right about the necessity for me to look out for articles and websites that follow the methodolody, I prefer. I do so. I stoped devouring articles about electronic gear, I don't believe them to have any validity. Either I don't read them at all or skim through them to see if there is some information, I can use.

For innerfidelity, there are parts or the site that are still interesting for me (like comparing headphones, which just is subjective and the efforts towards more measurements. Yes please! And of course Richard Stallman ocasionally commenting on free software =D). That's why I keep comming back, though I cannot consider every article helpfull anymore.

My rethorical question expresses some frustration because non subjective reviews and relieable measurements are hard to find. Also the remark should encourage you and other contributers to innerfidelity to continue to work towards more measurements and blind testing. For me, this would bring back some trustworthyness to the articles and raise my interest in them.

roskodan's picture

v281, cma800r, taurus, hp8 mk2... paired with hd800

could you describe each of em in one word, in regard to your sonic experience, when paired with the hd800

... i'll accept 'no' too, as a valid and meaningful answer

regards

Bob Katz's picture

Someone should check that out against anything else as a headphone amp. It's only money :-(

xnor's picture

15 ohm output impedance, no feedback, only 10W into 4 ohm ...

Nope.

Bob Katz's picture

Well, Nelson has designs with fractions of an ohm output Z I believe. But it's academic as I'm not going to spend $2000 on an amp right now.

cspirou's picture

Actually the output impedance is meant to be high because its a current driven amp. Similar to the Bakoon hp-21. It actually has added resistors to drop the output impedance from 600ohms. Personally I would rather try it with high impedance. Because its current driven it also means there is less power when you use lower impedance and more power when you increase impedance. This sort of amp was conceived for single full range drivers like Lowthers. For speakers this amp would be very limited however most headphones are essentially single full range drivers so it seems like it would be ideal for headphones. I actually have a DIY project to make an F2 modified for headphone use.

xnor's picture

15 ohm might be considered a current source for 4 ohm speakers, but not precisely for 30-300 ohm headphone loads.

Still, with dynamic headphones you will run into frequency response deviation problems. So I don't see how it is a good match, especially not for a blind test / comparison.
With mostly resistive planar magnetics you will see little difference however.

--

I don't think this makes much sense. If you want high output impedance simply put a resistor in series with the outputs of a 'normal' power amp, e.g. a few hundred ohm.

cspirou's picture

Like I said, the 15ohms can be easily modified to an output impedance of 600ohms so it's not a valid criticism. I agree that I wouldn't use it for the Burson/O2 comparison test but my commentary was more about how the F2 can definitely work for headphones. High output impedance is not always an indication of bad headphone behavior.

http://www.innerfidelity.com/content/musings-headphone-amplifier-output-...

xnor's picture

Sorry, I missed the bit about modifying the output impedance, but I still don't see a necessity to build such an amp. With a 'normal' amp you have the flexibility from ~0 to X ohm output impedance using a simple adapter.

I'm sorry, but what Jan Meier showed is not that high output impedance leads to better performance.
Let's ignore that his electrical model of a speaker completely ignores suspension compliance and suspension loss.. and go straight to what's happening:

If you feed a speaker an impulse the voice coil and diaphragm will start moving. At the end of the impulse this moving mass wants to continue moving - mechanical ringing - that's not what we want.
This movement induces a voltage. Now there are basically two options:
a) the amplifier has a high output impedance, little to no current can flow, the driver will keep ringing
b) the amplifier has a low output impedance, current can flow and the mechanical ringing will be additionally damped electrically

You can simply model this yourself. Without suspension losses and high output impedance the driver would keep ringing for a very long time. With low output impedance it would stop very quickly.

Jan measured the amplifier current which includes this "corrective" current which gets lower the higher the output impedance of the amp.

This is also the reason why you will effectively get a bass boost with high output impedance: the speaker wants to oscillate/ring at some low frequency, and high output impedance enables that.

zobel's picture

You are referring to, and defining what is called the damping factor of an amplifier, which as you know, is the ratio of an amplifier's load impedance to it's output (or source) impedance. The lower the output (source) impedance, the better the amplifier controls driver resonances and ignores load impedance variations.

Another good measure is the slewing rate of an amplifier, which, as you know, is the rate in volts per microsecond at which the output signal from the amp is capable of rising above, or falling below its zero point. These measurements used to be done routinely, and were usually included as part of the published specs of amplifiers.

hd 800's picture

Hi,

great review !

so for what i understood from the reviews, the violectric v281 surpasses the auralic taurus mkii and the icon hp8 mkii when used with the sennheiser hd 800 ? right ?

regards

John Grandberg's picture
I like all three amps quite a bit, but when push comes to shove the V281 in balanced mode is my top choice. Depends on what you are after though.... the Icon amp can be made to sound the smoothest and warmest of the bunch via tube rolling (and/or cranking up the adjustable output impedance). That may appeal to some users more than others.
doraymon's picture

Hi guys,
Thanks for all the very useful reviews.
I have the impression that the headphones amp section of the Wall of Fame is a bit dated.
May I suggest you run a full update of the section with tons of comparisons?
I know it’s not easy but hey, asking is never wrong!
Cheers,
Dom

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