Leckerton UHA-6S MKII Portable Headphone Amplifier Page 2

The UHA-6S In Action
The sound of the Leckerton UHA-6S MKII is everything I had hoped it would be. As you would expect from an Engineer who spends all day helping other companies use Cirrus chips in their designs, Nick Leckerton really knows his stuff. The sound from this amp is clear, detailed, and very natural. It's also absent any coloration, which means it may not satisfy some users looking for an audio band-aid to cover the flaws in their music or headphones. That's not what I value in an amp but I recognize that some people do; those users should probably look elsewhere.Those seeking a transparent sound should definitely read on though, because portable amps don't get much better than this.

My initial method of evaluation was to use the UHA-6 in its most basic form - as a portable amp being fed by a line-out dock connected to an iPod Touch. The most obvious improvement here is the ability to drive difficult loads more effectively. The iPod by itself can often struggle to produce acceptable volume levels with full-sized headphones---the HiFiMAN HE-500 and Sennheiser HD650 are two examples, both clearly lacking when driven straight from the iPod headphone jack. With the Leckerton set to high-gain mode both models have significantly more headroom, sounding more dynamic and controlled. But there's more to it than just volume and drive. From the iPod jack, neither headphone sounds all that clear or well defined. It's like a big wet blanket thrown over the sound---I actually prefer my V-MODA M80 over either model when driven straight from the iPod. But add the Leckerton to the equation and we begin to see why the HD650 and HE-500 are so well regarded. Softness is replaced by clarity and definition ousts vagueness. For such a compact amp I am very impressed with the performance.

Most people aren't die-hard enough to carry big headphones like those in a portable setup. A far more likely pairing would be something like the V-Moda M-80, B&W P5, or Beyerdynamic DT1350. With those types, an amp need not supply massive current or voltage swing. They simply require a clear, neutral tone with low distortion. It also helps to have great channel balance and a silent background, attributes the Leckerton has in full. I can't truthfully say that the UHA is a night and day improvement over my iPod when using the M-80. It's more of a subtle thing, where listening for long periods is easier. I find myself focusing on the music more intensely rather than being distracted and wanting to read a magazine or check my email while I listen. If the amp manages to keep me more engaged then it must be doing something right, even if it isn't quite so concrete as it is with the bigger/more difficult headphones.

Then we come to in-ear monitors (IEMs), which have a whole new set of requirements. They don't need much power at all, but are all about finesse and subtlety combined with high resolution. Obviously that quiet background and great channel balance comes in handy again, as does the gain switch. Setting the Leckerton on +0dB means a very wide usable volume range to play with. And then there's the matter of output impedance: with multi-driver balanced armature designs, the headphone impedance can vary wildly. Some of my custom IEMs such as the Unique Melody Merlin and the Lear LCM-2B dip extremely low at certain frequencies. The 3rd gen iPod Touch that I'm using has an output impedance of 7 ohms, meaning that interactions are likely to happen. The results from these interactions will vary for each IEM, but generally speaking it will lead to unpredictable peaks and dips in the frequency response as well as an unacceptably low damping factor. Adding the Leckerton with its sub-1 ohm output impedance will take care of that problem completely---you get to hear the IEM as it was originally voiced.

This impedance issue will not apply equally to all situations. Some portable players have higher impedance than my iPod Touch, making the problem worse, but others are lower. The new iPhone 4S for example is under 1 ohm and therefore more capable of driving wacky multi-BA IEMs without issue. In those cases the Leckerton would not offer as much improvement.

However, there are other things that the amp does in terms of refinement and clarity that can not be attributed merely to the impedance factor. This becomes especially apparent when driving an ultra-revealing IEM like the Heir Audio 4.A or Earproof Atom. Micro-detail, or the ability to resolve minuscule events in the recording, is noticeably improved. Sometimes this will manifest itself as non-musical background information---an audience member coughs, a metronome clicks, that sort of thing. Other times it will actually be part of the performance---subtle brush work on drums, fingers sliding on guitar strings, and that last bit of breathiness in a singer's voice. Both types are the sort of low-level details that are very present in live performances but require a quality playback chain to properly reproduce. The Leckerton just goes farther towards that goal than most portable players do on their own.

Going Above and Beyond
Tyll is making headway on his headphone amplifier testing rig - but it's still a work in progress. That's not a problem though because Leckerton has done something which very few amp manufacturers ever do: provide extensive measurements of his unit under different conditions and loads using the $10,000 Prism Sound dScope III. Leckerton shows us real world examples of how the amp/DAC behaves with regards to distortion, noise floor, and linearity. We also get to see an unnamed competitor with similar pricing and features as it struggles through (and ultimately fails) the same tests. In contrast, most amp makers will just post a single spec like "200mW at 32 ohms", which is neither very helpful nor very reliable.

Note that these test results are from the original UHA-6S model. Nick tells me he is working on finalizing test results for the MKII unit - so far they meet or slightly exceed the performance levels of the earlier design.

Other Uses
As I mentioned, a portable headphone amp is simply not on the radar of a lot of people. It's the extra features in the UHA-6S MKII that make it so appealing. To that end, I set out to try every possible configuration I could think of.

First I tried an Acer laptop which has a terrible integrated headphone output. Using the Leckerton via USB connection, the resulting improvement was significant - flat, lifeless sound with very little redeeming value was exchanged for excellent clarity and detail. Headphones that the integrated sound solution couldn't even begin to power were now capable of being driven to ear-splitting levels. This truly was a night and day transformation.

Next I paired the unit with my iPad 2 via CCK (camera conector kit) for some more USB DAC action. Despite being limited to "merely" 16-bit/48kHz files, I think this makes an excellent transportable combo. The iPad has an integrated DAC solution provided by Cirrus Logic (a CS42L63 to be exact), and it sounds pretty decent. But the Leckerton is packing the top of the line CS4398. Combined with the superior power supply and a Linear Designs LT6233 opamp handling low pass filtering, the Leckerton is by far the more capable unit. The result is audibly superior in almost every way.

The Toslink and coaxial digital inputs came in handy around the house. I paired the Leckerton with my Blu-ray player for some late night movie watching, making sure to select the proper settings for a 2 channel downmixed PCM output (the Leckerton obviously won't decode surround sound bitstreams). The unit did a better job than the headphone jack on my surround receiver, sounding more dynamic and having a blacker background. I've heard a few surround receivers that have decent headphone outs but those are the exception rather than the rule.

Getting back to portable use, there are still very few portable devices offering digital outputs. An iPod paired with the Cypher Labs Algorhythm Solo or Fostex HP-P1 will do the job. Some people are still using the venerable iRiver H100 series players. I chose the rather uncommon path of using a QLS QA-350---it's a brick with a tiny display, poor battery life, and it only plays WAV files, but it does have digital outs and the price is right. I find that it's worth lugging around this combo when I want to experience "at home" quality sound on the go - something that is rarely achievable without spending a good deal of money.

The Leckerton UHA-6S MKII is a spectacular performer. I used it in many different scenarios, fed by various sources, driving a wide range of different headphones, and it never failed to impress me. I've owned more expensive portables than this, and more powerful ones too, but at this moment the UHA-6S MKII is my number one recommendation. Kudos to Nick Leckerton for improving on his earlier model, which I didn't think could be topped. Well done!

Leckerton Audio Inc.
401 Congress Ave
Suite 1540
Austin, TX 78701

Long time listener's picture

The Leckerton does sound like a great piece of equipment. But for portable use, especially with IEMs, I've found that having tone controls, like those on the Fiio E-17, is invaluable for getting good, balanced, and satisfying sound. I know ultra-purists will say that running the signal through tone controls introduces distortion. Yes, I'm sure it does, but not enough to outweigh the huge advantages of being able to balance sound that might otherwise be very unbalanced. Why don't more companies put this feature on their amps? The Fiio sounds only average as a DAC, but the amp section is not too bad and with a really clean input signal, plus the tone controls, it sounds really great. So I won't be buying a Leckerton any time soon, no matter how good it may be in all other respects.

John Grandberg's picture

You have to go for a product that has the features you want or need, above all else. It's like wanting to buy a sports car but having to "settle" on a big sedan so you can fit your family in there.

Another example: the smaller/cheaper Leckerton UHA-4 has crossfeed. Some people absolutely demand crossfeed. So obviously they would choose that model over the 6S, even if it isn't quite on the same level in overall performance.

Gelocks's picture

Thanks for the review.
I've been "eye-ing" this unit for a while and haven't bitten yet... You know what this review lacks? Comparisons against other devices! How does it fare against Fiio's?!? How does it compare against the c421, and countless others?


John Grandberg's picture

For the portable amps I currently have on hand, there is no competition - the Leckerton is hands down superior when it comes to the overall package. I may not have every single relevant model on hand for comparison - but I do have some.

The c421 is a nice sounding amp and I dig the bass adjustment feature. The 10 ohm output impedance is not ideal, and it does become a headache with some of my custom IEMs like the UM Merlin.

The iBasso D10 is totally outclassed by the Leckerton. I've heard the D12 and also find it outclassed, though I haven't had enough time with it to speak definitively. I think there are some serious design/implementation flaws in these things that are holding them back. They use all the "hot" chips but the end result doesn't quite add up.

I haven't heard the Fiio stuff. The E17 looks like a good buy even just based on sheer features. The person leaving a comment above you mentioned he/she thought the DAC part was merely decent, though obviously that's just a single voice in a sea of opinions.

I've got various other portable amps around from Audinst, RSA, iQube,and some others, and I prefer the Leckerton to all of them.

Gelocks's picture

Thanks! (I hadn't noticed this reply! ;-)).

dalethorn's picture

The Audioengine D1, Headstreamer, and Dragonfly sound similar to me and significantly better than the FiiO E17 as USB DAC's when playing 96 khz tracks. So I wonder if this DAC/amp could beat the aforementioned 3 when playing 96k tracks from USB? Since it's limited to 48k.

zobel's picture

What advantage is there to a higher sampling rate than 48k?

dalethorn's picture

There is a great deal more audio information in the 96k track. Some people say you can't hear it, and others say you can somehow hear the 'effect' of it but not any real additional musical info. To me the sense of 'space' and 'air' in the 96k tracks are usually better, but proving such a thing is difficult.

But when it comes to testing amps, I can sure hear the differences with some of the 96k tracks I have.

John Grandberg's picture
We can argue all day about the benefits of 96kHz (yes I'm aware of the Meyer/Moran paper and the subsequent arguments against it) but I think the answer is simple: I've got a lot of music in 24/96. I paid money for it and want to be able to play it back. In many cases, the 24/96 release is a different master than the original 16/44.1 release, usually for the better. So even if we conclude that the higher sample rate has no inherent value, I still want to be able to play these superior albums in their unmolested state.
mikeaj's picture

From a technical point of view, a clear advantage of the higher sampling rate is being able to capture and reproduce more frequencies (higher than 24 kHz). For audio playback to be consumed by humans, these ultrasonic frequencies have some questionable value, but there are other things going on as well. To call any ultrasonic content as "audio information" may be a stretch though, unless you're a bat.

If you don't mind wading through holy wars, check out the aforementioned Meyer and Moran paper, peoples' opinions on that, and their response to their opinions. No need to rehash the whole thing here.

But as John pointed out, there is a practical point to having a DAC that can handle a higher sampling rate. A decent amount of music is released that way, and sometimes these are higher-quality masters. You could play back a 96 kHz file on a system that doesn't support it by resampling down (and some software can do on-the-fly resampling that's unlikely to have any perceivable negative effect), but it's good to just be able to play back the file natively.

dalethorn's picture

So the extra bits are only for high frequencies? There's no phase or timing info or other things in the extra bits?

John Grandberg's picture
I agree that we shouldn't rehash the debate here - it isn't the best format and frankly it has all been said before. I suspect that most people already have their minds made up anyway, so the argument would be an exercise in futility. That's why I've focused on the convenience factor of it, which certainly *can't* be debated. My daily setup recently has been the Meizu MX-Quad smartphone feeding coaxial SPDIF out to the UHA-6S mkII. Since the Meizu will play FLAC files at their native rates, I can simply load up the phone with some of my favorite albums. I don't have to worry about the albums being hi-res. It's really convenient for me. I love my Sansa Clip+ as a cheap and tiny player, but it really limits my library since it can't do hi-res.
dw1narso's picture

Beautiful write up, John.

sorry if this would be a bit out of topic, since you mention about Meizu MX. Does Meizu MX has SPDI/F port directly? or is it in a kind of USB to SPDI/F converter?

John Grandberg's picture
I'll have a review of the Meizu MX-Quad up soon. But to answer your question - SPDIF is carried through the USB port, through use of a "breakout box". I've got an engineering sample which is PCB, chips, and ports, but no enclosure. I'm sure the finished design will be more streamlined. Maybe about the size of the Camera Connection Kit from Apple. It would have been ideal if they had a straight coaxial SPDIF port but there really isn't room.
zobel's picture

I'm aware of the bit depth / sampling rate debate, just wanted to get some feedback from those of you who have these files and are enjoying them on players that support them.

ultrabike's picture

Thanks John! Very well put together review.

Long time listener's picture

I'd just like to thank John Grandberg for the friendly and polite response to my post, the first in this thread. The best way to disarm your critics is to agree with them; his response is one reason I now have a highly positive impression of Leckerton as well. I have little doubt that its DAC at least, and likely the amp as well, do significantly outperform the Fiio E17. When used as a USB DAC-amp combination, the sound of the E17 to my ears is pleasing but not highly resolving as it still has a trace of graininess. It's just that, in addition to the lack of portable sources with digital outs, finding a DAC/amp combination that allows you to tailor the sound to your liking is an extra source of frustration. If Leckerton ever makes such a device I will snap it up at my first opportunity.

(For those who are interested, I get really great portable sound with the following: A HifiMan HM-801 feeding from its line out through a DIY connector of Jena Labs 7N copper wire to the Fiio E17, using a pair of Ultimate Ears Triple-Fi 10s with the dedicated Fiio upgrade cable made for them. And using the tone controls.)

star's picture

Sounds great, but...
Submitted by Long time listener on July 20, 2012 - 12:44am.
The Leckerton does sound like a great piece of equipment. But for portable use, especially with IEMs, I've found that having tone controls, like those on the Fiio E-17, is invaluable for getting good, balanced, and satisfying sound. I know ultra-purists will say that running the signal through tone controls introduces distortion. Yes, I'm sure it does, but not enough to outweigh the huge advantages of being able to balance sound that might otherwise be very unbalanced. Why don't more companies put this feature on their amps? The Fiio sounds only average as a DAC, but the amp section is not too bad and with a really clean input signal, plus the tone controls, it sounds really great. So I won't be buying a Leckerton any time soon, no matter how good it may be in all other respects.

so whats relative here ,can someone pinpoint one,' that would encompass both worlds in it ? or can someone influence lacktorn audio to add ' the missing tone controls ?

dalethorn's picture

Using the DAC/amp as a portable with small music players, those players are going to be amped in analog mode, and the tone controls on the music player would do the work. Most music players even have advanced equalizer options, either built in or available as apps. If you were using the DAC/amp as a USB DAC and headphone amp from a laptop computer, the tone controls (equalizer) in the music player app like iTunes or Foobar would also do the job. In that last case, I haven't figured out yet where the tone controls are actually applied, but it works that way with the three small DAC/amps I have now and I assume it would work the same way with the UHA-6S.

Long time listener's picture

Yes, you're obviously right about all the options you discuss above. I've gotten locked in to using certain equipment--the HM801--and as much as I think it's tremendous as a DAC, it doesn't drive IEMs well, and its on-board equalizer is very poorly implemented and mostly useless as far as I can tell. And I'm mostly interested in portable options rather than laptops, so for IEMs I wanted something with tone controls on board. And what I'd really like is a good portable source with a digital out that can feed into something like the Leckerton, but that would offer higher quality sound than the Fiio E17, plus a full package of features, including tone controls. I guess I just don't know why such things are so difficult to find.

dalethorn's picture

It does seem that the so-called audiophile music players can get very expensive. The iPods with i-device DACs are certainly not portable in my view given the number of components and cables required, not to mention sound that's not as good as what's the topic here.

And I don't know if this is worth mentioning, but Sony and perhaps a couple other companies make miniature PC's that are nearly pocket size, and if those have real USB ports, that might do the trick.

star's picture

my question is ,then which would encompass both worlds ,high quality like lacktorn audio and control like fiio e17

using a portable mp3 player which have no built in EQ

AncientWisdom's picture

The best solution would probably be getting a good quality mp3 player with goods eq or one that can be rockboxed.

AGB's picture

Some of these issues discussed wil be moot soon enough.

Apple is changing to a miniaturized iConnector for all new iProducts.

The wider connector at the bottom of your iPhones and iPods are gone.

At this time I'm not sure if those licensed to get the digital streal off these iThingies will have the license or even the ability to get the iStream going again.

Clearly most of the iDocks out there will be obsoleted.

iMafraid we have an iProblem here.

On another matter, we need iCapable players with iZotope processing like Amarra's and Fidelia's to get good sound -- and EQ to get better sound.

I also agree, if this is not possible, the Leckerton should have some sort of EQ capability (tone controls? Ugh!)

Otherwise iMf-----d.


star's picture

can you tell more about this,can this be implemented into any portable cd player or and laptop media player ?

bugmenot's picture

It also appears to work properly with USB On-The-Go.


eyal1983's picture

Did someone compare these ?

izzmeth's picture

Hi. I would like to buy one of these. does anyone have an idea whether the UHA760 is just as good as the MKII. Don't need optical and coax. for 120 dollars more I want to know (1) is it worth the extra money (2) does the 760 at least match the MKII in quality? thanks in advance for any thoughts!

Muntasir Tanvir's picture

Hi...currently i am using sennheiser HD598..audiotechnica m50x..hifiman re400 and a little sound enhancing device called reveel..

recently i bought a HD800 from a freind of mine for only $700...and it was almost brand new..so even though i dont have an amplifire to drive...i bought it anyways..now i dont have the money to get a hi end amp for $2000...i was wondering can the Leckerton UHA-6S MKII drive the HD800..Im considering to buy one for the time being until i have enough money to get a decent tube amp...guys plz help!!!

AndrewG's picture

I'm interested to hear anyone's thoughts on the Fiio E18 compared with this amp.

Awee3's picture

Games PS Vita You guys are even bigger fans of Ninja girls, then you can catch you the limited edition of Bahonkas. It comes with all the above bonuses, as well as with a two-sided Dakimakura pillowcase.
PS Vita Games