Leckerton UHA-6S MKII Portable Headphone Amplifier

Portable headphone amps are an interesting segment of the market. On one hand they are quite popular, generating a large amount of discussion on HeadFi. On the other hand, a lot of headphone enthusiasts have never used one. I suspect these people do the bulk of their listening at home on a dedicated setup, and just go straight from the headphone jack of an iPhone or other player if they end up listening on the go. I can identify with that mindset - a simple, lightweight, compact solution is very desirable for mobile use.

There are other factors keeping people from using portable amps aside from the extra bulk. For starters, many portable situations don't lend themselves well to critical listening. Activities like jogging, carpooling, or mowing the lawn aren't exactly times where you concentrate heavily on your music. So even if a portable amp has potential to offer a nice upgrade in sound, for many people it just isn't worth it. And then when you are at home in a quiet environment where it would make more of a difference, a portable amp will almost always have less to offer than a comparably priced desktop unit. I can certainly identify with people who are not the least bit interested in these devices.

But what if the portable amp had more to offer? How about a nice DAC section with multiple input options? What about adjustable gain to ensure it pairs well with a variety of headphones? How about socketed opamps to facilitate customization? Features like these transform an ordinary portable amp into a more useful multi-purpose device.

Jack of All Trades
Based in Austin, Texas, Leckerton Audio is a small but increasingly popular firm that deals solely in portable amps. By day, owner Nick Kettman works as an Application Engineer for Cirrus Logic, helping other companies implement Cirrus chips into their products. He's also been offering portable DAC/headphone amp units under his own name for over 5 years. Unlike some competitors, Leckerton does not release a new model every few months, which could be seen as a good thing or a bad thing depending on your perspective. The UHA-6S MKII is his newest model - building on the already well regarded UHA-6S, the MKII adds several important features while keeping the same $279 price.

The new model is just 70mm x 84mm x 20mm and has rounded edges for a sleeker look. It's got the usual 1/8th" jacks for input and output like nearly all portable amps. Charging is done through the rear-panel micro-USB port, which can also link to a computer for USB DAC functionality. SPDIF digital connections are also offered in both coaxial and Toslink form, an array which is not often found in a portable unit like this. The SPDIF inputs are functional up to 24-bit/96kHz while USB tops out at 16-bit/48kHz. The somewhat limited USB implementation is used to maximize iPad compatibility - using the Camera Connection Kit, a digital stream can be extracted from an iPad without needing a dedicated unit like the Cypher Labs Algorithm Solo. There are some hi-res capable USB chipsets that will interface with the CCK but these older 16/48 types tend to have better compatibility.

Power is supplied by a Lithium ion battery which has a life of approximately 30 hours using the analog input, or 10 hours when fed through an SPDIF input. A switch allows charging to be disabled in order to preserve laptop battery life. Gain can be set at +0dB or +18dB to fit a wide range of headphones.


The guts of the device are packed rather tightly. Considering the amount of features, I'm impressed at how small Leckerton was able to make the enclosure. The original UHA-6S was comprised of two separate boards sandwiched together - one for the power supply and DAC, the other for the amp section. This update fits everything on a single PCB which makes for a thinner device overall, though it is slightly wider.

USB signals are received by a TI PCM2706, transcoded to SPDIF, and sent to the Cirrus Logic CS8416 digital interface receiver. The DIR also handles incoming signals via coaxial or optical connections. The DAC section is based on the flagship CS4398 chip from Cirrus Logic.

The power section is well done---a DC-DC power supply generates isolated + and - 6 VDC power supply rails. This means no "virtual ground" is necessary and no DC-blocking capacitors in the signal path are required. This bipolar conversion is the most expensive way to do a battery-powered DAC. It also takes up more space and draws more power than other methods such as inverted charge pumps or rail splitters. But for pure audio quality this design is as good as it gets.

The amplifier output section is centered around a pair of single channel socketed opamps. The stock configuration uses the OPA209 but other options like AD797, AD8610, or OPA627 can be had for an extra fee. The original UHA-6S came with the AD8610 stock, but the OPA209 upgrade became so popular that Leckerton is now using it by default. Output impedance is suitably low at 0.4 ohm thus preventing any impedance-related interactions.

From a technical perspective, this all adds up to a device that should sound excellent. But does it? Read on to find out.

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.

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