Shortest Way 51+ or

Im looking to buy a tube amp (OTL/SET/Hybrid) under 400$ to pair with Hd6xx.

Since i’m in Asia, import taxes add 40% to the price so anything around $400 costs close to $550 for me. This is my first proper tube amp, had been using a tube pre-amp (FX Audio Tube 03 Mk2). Though not a proper tube amp, it adds some mid range holography and soundstage which got me hooked and now chasing that smooth, holography and soundstage sound signature.

Off the shortlist, Sw51+ looks interesting. Valhalla2 is available here but i gather its a dryish amp, doesnt have tubey liquid/wetness in sound. Lyr 3 is also an option that pairs with 6xx (and Arya v2 in have), but not sure if has that tube liquidity.

Would love to hear owners impressions and comparisons with similar priced tube amps. In case there is already a thread on this, please point me in the right direction


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Depends a lot on what you are looking for.
A lot of higher end tube amps are not “tubey” in the BHC/Dark Voice/cheap tube buffer sense, they do add some weight to the midrange, and a hint of sweetness, but many aren’t the oooey gooey sound a lot of people seem to associate with “tubes”, they are just more natural sounding amps than a lot of SS amps.

The SW51+, which I consider to be a bargain for the performance level, with the supplied Soviet tubes is quite dry, even with the NOS Mullard EF184’s (which was my preference) it’s on the dryer side. Haggerman Tuba and the Quicksilver skew the same way, with the former being comparable IMO and the latter a step up.

If you can find a ZDT Jr, ideally with the transformer fix, those work very well with the HD6??, and are a nice middle ground between the very wet amps and the totally dry presentations.

Bottle Head Crack is a great amp, but it’s on the very wet side, the speed ball adds a degree of refinement, but doesn’t make it dry, works stunningly well with the HD6??, but for me it could only ever be a change of pace, nice occasional listen, not my only amp, the ones above could.

The Cavali hybrids, (CTH and liquid Plat) both sound like SS amps with a slight hint from the tube, the liquid plat when it’s on sale for <400 is a bargain, but might not be what your looking for.

I haven’t heard the Schiit or Felix amps.

There is so much personal preference in these selections, as I said at the start, depends what you are looking for.


Thanks for responding. Quite right about personal preferences and this changes everything!

So to understand better… in terms of liquidity/gooeyness on one end and dryness/solid state sound sig. on other end, this is how these amps sit - Darkvoice > BH > BHC > ZDT Jr. > SW51+ > Quicksilver >ZMF Pendant/ DNA etc.?

I understand that electrically, the high impedance transducers work better with voltage gain and high output impedance amps, so technically its a better match. But i’m curious to understand is that if the likes of Tuba & Quicksilver perform similar to solid state counterparts (say Singxer SA1 or Burson 3XP), then what ‘sound sig.’ aspects do these tube amps offer, that differentiates them solid state counterparts?

In a nutshell, i’m trying to get the sound sig. of BHC (i.e. laid back, wide staging, longer decay/reverb, euphonic) for less. The way i see it - the SW51+ sits perfectly in that budget category offering higher class perf., albeit at a marginal comprise on liquidity/wetness; comparable to likes of BHC/ZDt Jr. Would that be an accurate assessment?


Not sure about this, but I thought that the SW51+ was only available to members of the Super Best Audio Friends forum. If you want the Bottle Head Crack sound
signature I would also consider Eufonika Audio from Poland. They build really nice sounding headphones amplifiers for the price. An H5 is very similar to the Bottlehead Crack and for a bit over $400 US. If you are looking for real bargain the Little Dot MKII is a terrific little
OTL headphone amplifier for under $200 US.

Best of luck in your search! :blush:

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Quicksilver is dryer than the DNA a amps, but the ranking is about right.

On sound signature, it’s just not in your face, all tube amps I have add a degree of body, generally they stage bigger. They also IME tend to do better with tonal texture, timbre and micro dynamics than SS counter parts, where as (and I’m generalizing) SS amps can have better macro dynamics, and at the price points we’re talking here will be blacker.
DHT’s also tend to have another quality that’s hard to describe, I’d refer to it as immediacy or presence.
Overall that combination leads to what I would generally term more natural sounding

We can discuss the why, it’s not the obvious distortion, tubes are more linear voltage amplifiers than transistors, there are also SOME aspects of tube rectifiers that are superior to SS solutions. Most tube amplifiers also have little or no negative feedback, and a lot of negative feedback is common in lower priced SS amps, and that tends to impact Stage, and micro detail first.

For the HD6?? Specifically the reason it comes up is that with the higher output impedance of lower priced tube amps (tube amps can be under an Ohm) tends to fill out the bass and treble frequencies a bit. The HD6?? suffers from being a bit of a one trick pony on lower end sources, it has fantastic midrange (much better than it’s price point) and not a lot else, with the right tube amp they can sound MUCH a better than their price point.

One final comment, I guess I must like tubes, because I no longer have a SS amp I use regularly, and there isn’t one that interests me in the headphone space. But that has nothing to do with liking tubes, it has to do with preferring equipment that happens to use them. It’s just another way to skin a cat.

My somewhat controversial position on tube amps is that for the most part they don’t make sense at lower price points, there are exceptions like the ones mentioned in this thread, but they don’t IMO get really good until you get to higher price points. It’s purely a function of component cost, good output transformers are expensive, and they are massively dependent on the quality of the power supply.


Thanks for the tip. will definitely check them out!

Thanks for the valuable insights Rob…very helpful…seems like im going to enjoy tube amps for a long time to come…as most of my gear revolves around ‘natural’…!!

Glad to be of help. :blush:

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I’m afraid this post won’t be add much to what’s been posted already, @Works4treats, but I’d like to echo what Polygonhell has written, and at the very least I can offer another data point for you.

I’ve got the Massdrop Cavalli Tube Hybrid, the ZDT Jr., and the SW51+ and I also have the HD 6XX.

The ZDT Jr. is the best of these three amps for a deeper, wider, more three-dimensional soundstage and for tubey gooey pleasure. It’s a great amp. One limitation of it is that its bass isn’t the tightest but I’d assume this isn’t a priority for you given that you like the HD 6XX. The ZDT Jr. is quite warm, depending on the tubes you use, and the treble isn’t the most well extended, which partly explains that warmth.

The MCTH has a significant bass emphasis but, again, it’s not the tightest, and it can be a bit boomy. The midrange is decent but not very rich, and there’s a bit of treble emphasis. The MCTH’s pairing with the HD 6XX is decent enough; it’s quite clean and has strong macrodynamics - drums sound nice and quick and strong and clear - but this is a far cry from the tubeyness or holography you’re after. I’d skip it for the HD 6XX.

The SW51+ is a neutral amp. I’ve not thought of it as dry but then I have the Bifrost 2 as my DAC; I’ll go listen for this dryness when I get from vacation. It may be something I’ve overlooked. Again, this amp’s not ideal when it comes to tubeyness. But it does have plenty of magic with the mids. Of the three amps, it pairs the best with the HD 6XX according to my preferences (which, to be clear, are in favor of the HD 600 over the HD 6XX, which I find too warm, especially with the Bifrost 2 and ZDT Jr.). The soundstage of the SW51+ has acceptable depth. It’s not three-dimensional or very spacious, but with the HD 6XX, it’s quite wide. Imaging, layering, and separation, though, are excellent, for the price (and compared to the other two amps).

I’m afraid I’ve not heard the Valhalla 2 and my experience of the Lyr 3, from brief auditions, is entirely insufficient to warrant offering any comments.

You might also consider the Vali 2+. I’m not sure how well it pairs with the HD 6XX but I know a number of people whose ears I trust who have commented on its quality with the high-impedance Sennheiser amps. It has the advantage of being well under your budget, and it may well punch above its weight, especially if you can’t get ahold of the others we’ve been discussing here.

Your best place for info about the SW51+ is over on SBAF. Sign up! You don’t have to be a well-established member there to order the amp (I’m not sure if you actually have to be a member although the maker of the amp, Zampotech, originally made it for that community). I’m not sure if he’s currently taking orders for a new batch the amps - you should check his recent posts.

Good luck!


Thanks @Tchoupitoulas… you’ve answered it for me :smiley:

I know soundstage width is not great on the 6xx but with the Ares2 dac its more than satisfactory. I tend to go for Ares2 when listening to jazz quarterts/trios or classical. On the modi multibit v2, its relatively intimate and thus my go to for solo vocals etc. For electro, etc. .genres, mojo is my goto so to your point, i agree that the BF2 wont sound dry. The point of getting a tube amp was to sample the tube magic in the mids, and if does imaging, layering and separation well, id be pretty happy (esp. given the price). Would love to hear your impressions, post the vacay (have a good one!)

Ive been chasing Zampotech for a month and he has been generous enough to make ‘just one’ for me :slight_smile: All this searching is just the human need for validation (or avoiding buyers remorse :P).

Now that @Jimmyblues has shown me a treasure trove, i have much reading to do on Eufonica. at the outset, i’m quite impressed with what i see!! Thanks Jim, this is quite a find :smiley:

Sidenote - loving this community!!


Glad to be of help! I think you will be very pleased with a Eufonika headphone amplifier. Eufonika,
and its owner, Wieslaw, are two true gifts to the head-fi hobby. I’ve been using a Eufonika H4 output
transformerless headphone amplifier for more than a year, and really like how it synergies with my Sennheiser HD600, HD6XX and AKG K240 Sextett.

Best of luck on your hifi journey! ��


Congratulations! That’s great news.

I understand completely. If I were you, I wouldn’t worry. This little amp really is as wonderful as it is made out to be. For the price, it’s astonishingly good. Overall, I prefer mine to the ZDT Jr., but I keep this latter amp because it does great things to my HD 800 SDR. Surprisingly, the SW51+ collapses the large soundstage of the HD 800, thereby undermining one of that headphone’s qualities. But, otherwise, the SW51+ is entirely satisfying.

While I may value other headphones for certain qualities or purposes, I think with the Bifrost 2, SW51+ and HD 600 I’ve landed on a setup that is incredibly pleasing, rewarding, and entirely satisfying. It may not be the most technically accomplished setup. Nor does it have the best bass or treble extension. But the timbral and midrange richness, the high resolution, the engagingly strong macrodynamics, and the excellent layering and clear separation, together with the reasonably spacious sound - one that has plenty of air and space around instruments, in part, thanks to the precise imaging - all these things and more make for a highly engaging and immersive listening experience. This is the first setup I’ve heard where I’m entirely content to turn down the volume. And I find myself freed from wanting to analyze what I’m listening to. I simply get engrossed in the music.

I realize all these laudatory comments might come across as overly enthusiastic. But I should add that this past summer I’d been pretty burnt out from work and other things. Tired, my concentration span had been frustratingly short. I’d not been in a state of mind to appreciate entire albums, much less longer classical music compositions. The SW51+ and HD 600 pairing helped get me absorbed in the music again.

The SW51+ also pairs quite well with some of my other headphones. It does a decent job with my Focal Clear. The MCTH gives the Clear an exciting, highly energetic presentation; the softer, more rounded transients of the SW51+ make for a mellower listen with the Clear. I’m also enjoying my Vérité Open with the amp although I’m still finding my way with the sound and am not ready, yet, to formulate an opinion.

Given the amp’s many strengths, I can see myself holding on to it for the long-term, even if decide to upgrade to a DNA Starlett or other, higher-tier SET amp. I hope you enjoy yours! Remember, it doesn’t come with a power cable - be sure to have one to hand for when it arrives!

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@Works4treats I own the SW51+ and can echo what others here have said about it. Looks like you already have one on the way to you, so you should be set. I also own and enjoy the Quicksilver, which I agree is a step up in general, but it’s also 3x more expensive.

I think I’ve mentioned this before, but if I had gotten SW51+ before I had ordered the Quicksilver I think I could have been perfectly happy with it as my only tube amp. It didn’t help that it was my first tube amp, so I had nothing to compare it to. I didn’t fully realize how much value it offered for its asking price until the Quicksilver barely edged it out at a much higher asking price. Funnily enough, the Quicksilver seems to punch well above its price bracket as well. I’d like to hear some high-end tube amps one day, but I’m pretty satisfied with my two bang-for-the-buck champs.

Don’t forget about the importance of synergy as you move forward. I clearly preferred the Quicksilver with my Verite Closed, but with my Auteurs, the SW51+ is making a case for itself as the better match. I used the Bifrost 2 as the DAC with both setups.


Yes, thats the idea! Im already excited to hear the amp now!

Actually i dont mind even if they superlative/glowing. In my profession (mgmt. consulting), music is what keeps me going through the daily 12 - 16 hours of slog, so yeah, i get the burnout aspect. for me, its my lifeblood, keeps the life rhythm going!!

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