Review on my site: https://jamesfiorucci.wordpress.com/2024/05/11/simple-audio-review-fosi-audio-sk02/

Fosi Audio are a Chinese HiFi brand famous for their budget audiophile gear. They make a variety of dongles, DAC/amps, preamps and more, with the majority of their products falling below $100 in price.

Their latest DAC/amp, the SK02, is one of their pricier units at $119.99, but can still be considered a budget-friendly device. Its development and manufacturing was funded with the help of a Kickstarter event; boasting over one watt of power and a huge knob (!) on a compact frame it was bound to secure the funding from the get-go.

The SK02 has been out for a few months now, and admittedly I’m a little late to the review party. I’ve been inundated with a mountain of gear which needs reviewing, which to be fair is a brilliant problem to have! This little DAC/amp has received plenty of positive reviews and is already being lauded as a benchmark in the sub-$150 price category.

Question is, do I agree with the general consensus regarding the little Fosi? Let’s start with what’s included.

Thank you to Cathy from Fosi Audio for organising a review unit for this evaluation.

What’s Included​

You don’t get much with your SK02. The box itself is a simple cardboard affair, and inside is the DAC/amp itself, the USB cable to connect to your playback device and a user manual.

Focussing on the cable, I’m a big fan. I love the interchangeable USB-A and USB-C connectors which are attached to one another. Makes it easy and simple to swap between using the SK02 with your mobile phone and your PC, as an example.

Clearly, the vast majority of Fosi Audio’s budget has gone into the unit itself though. Onto that then.

Design, Build and Features​

The shape of the SK02, along with its unique top-mounted volume knob, is reminiscent of the Micca OriGen series of DACs. The location of the volume control makes it easy to make adjustments, although I do wish it had a mark on its surface so you could remember preferred positions for certain headphones.

I think the whole layout of the LED indicators on the top of the unit to denote the sampling rate, and the simple gain and mode buttons to switch between high and low, and USB and optical respectively, are simple to understand and easy to read.

The knob itself functions as a play-pause button with a single press, and as a mute button when double-pressed. This is a feature I wish to see more on other similar devices.

At the front there is a single-ended 3.5mm and balanced 4.4mm output. And at the back is the USB-C input which acts as the data transfer and power draw for the device. The SK02 can be used as a standalone DAC courtesy of its aux/optical output, and as a preamp using the optical input.

Moving onto build, this is one sturdy piece of kit. It is manufactured out of an aluminium alloy that adds considerable heft; you could use the SK02 as a blunt force weapon in a pinch!

The weight, as well as the overall chunkiness of the unit means it’s not quite as portable or transportable as the small footprint may suggest. It will most likely stay firmly put to one side of your desk.

Sound and Synergy​

With a headphone output power of 1,100mW (@32 Ohms) from the balanced connection, the SK02 packs a serious punch. It’s certainly the most powerful amplifier that I’ve come across at its price point. The unbalanced connection still provides plenty of power with 280mW at 32 Ohms.

Suffice to say the SK02 will provide more than enough volume for even the most demanding and power-hungry of headphones. But will you want to? I’m not so sure, let me explain by describing its sound.

This is a very neutral-sounding device, with a slight sharpness to the treble frequencies which at times makes it sound a touch bright. This feature is a double-edged sword, pairing well with bassier headphones but accentuating any sibilance or harshness apparent in treble-focussed headphones.

Take the Beyerdynamic DT880 Edition 600 Ohm for example. It is renowned for its elevated treble, but with a decent enough amplifier the upper frequencies can be smoothed out quite nicely. Unfortunately this is not the case with the SK02, which not only has that slightly bright characteristic but also doesn’t have enough juice to tame that typical Beyerdynamic treble spikiness. Admittedly I could only use the unbalanced output with the DT880; perhaps it would have had a better time of things with a balanced connection.

I enjoyed the SK02 with my Denon AH-D5200 as well as the Sony MDR-1A. Both of those cans are on the bassy side, and the slight etch to the treble helps bring out the sparkle and details that otherwise can get lost around the heightened bass. It also helps that the SK02’s extension on both extreme ends of the frequency response is very good, and macrodynamics is decent too.

Imaging and soundstage performance is subpar on the SK02. This only becomes an issue on headphones that image particularly well, like the Audio-Technica ATH-R70x. The soundstage was squashed in by the SK02 and the layering capabilities became a little muddled, but don’t get the idea that it’s bad. It’s just about middle-of-the-road in the sub-$150 price category for integrated DAC/amps.

Overall Verdict​

The Fosi Audio SK02 DAC/amp impresses with its simple yet user-friendly design and jaw-dropping power output for its budget pricing. When it comes to the sound performance however, the SK02 is not without its flaws, but for $119.99 it’s really just a nit-pick.

Rating: 7/10​

Full review: https://jamesfiorucci.wordpress.com/2023/01/16/simple-audio-review-koss-porta-pro/

Recently, my dad had been complaining about his ear buds not fitting him correctly and constantly falling out. This had curtailed his music listening enjoyment, so in an effort to help him appreciate good music again I bought him a pair of Koss Porta Pros.

These are on-ear headphones, and thus aren’t going to fall off nearly as easily as a pair of IEMs. Furthermore, I had heard great things about the Porta Pros, lauded as one of the best sub-£50 headphones that you can find on the market today. I was sure he was going to notice the increase in sound quality (and comfort), but a couple hours later he handed them back to me with a disappointed look and said he didn’t like them.

I have my theories for that, which I’ll touch on in this review, but I decided to just keep the Porta Pros for myself and see (or listen) to what all the fuss was about. And lo and behold, I was immediately taken aback by the sheer value that these on-ear headphones present to the industry. Let’s dig deeper!

Comfort and Build

The Koss Porta Pro was designed in the 80s, and you can see that in its retro look. It’s crazy to know that Koss are churning these out new even to this day. Unfortunately, the retro influence stretches to its build too, with an almost all-plastic housing and thin metal headband. You can’t afford to be too rough with these cans.

Nevertheless, I found comfort surprisingly good with the Porta Pros. Weighing a mere 60 grams including the non-detachable cable, I find that they simply disappear on your head. Since the clamp isn’t too loose or too tight, the lack of padding on both the ears and headband don’t cause any comfort issues. I didn’t find myself ever using the “ComfortZone” toggle on the sides, but I guess that’s an added benefit to have.

The mechanism for adjusting the size of the headband is a weird one; let me explain how I found was the best way to fit the Porta Pros correctly on your head. First of all, adjust the black sliders on the headband to maximum size and put the headphones on your head. Then simply slide them in the opposite direction to reduce the size until it is secure. Just try not to get any hairs stuck in the gap between the metal sheets of the headband; trust me it hurts!

Sound

Expectations were low for such a cheap pair of headphones which look like they could come out of a McDonald’s Happy Meal, but these blow all assumptions out of the water as soon as you hit play on your favourite tunes. Of course, there are a few shortcomings, but they’re really only noticeable if you go searching for these faults.

Bass
The drivers found on the Koss Porta Pro were designed and first manufactured in 1984, so it is of no surprise that they don’t quite extend down to the lowest frequencies. This will lead to some genres, such as grime and EDM, to sound somewhat lacking.

Strangely enough however, bass is one of the redeeming aspects of the Porta Pro. There is a significant mid-bass bump which gives a satisfying level of kick and thump to instruments that demand it, such as drums and bass guitar. It also contributes to an overall warm tonality, which results in a thick and full-bodied weight to the music. I tend to prefer a warmer sound signature so I like this characteristic of the Porta Pro, but I understand it is not for everyone.

Midrange
Honestly I don’t have a whole lot to say about the midrange. Despite the mid-bass emphasis, the mids don’t feel recessed whatsoever and have a naturalistic timbre that bodes well for the vast majority of instruments.

The upper midrange does come across as “shouty” on some tracks, but that has more to do with the recessed treble region that I will get onto in a little bit. For this reason, female vocals can seem to overpower the rest of the mix. This, along with the proximity of the drivers to the ear canal results in listening fatigue for me personally, but it does take a few hours to kick in.

Treble
The recessed treble is probably the reason why my father disliked the Porta Pro’s sound, which is understandable. What I would describe as “warm and relaxed”, he would call “muddy” and lacking in absolute detail.

It’s crazy how some songs sound completely different with the Porta Pros. Those sparkly notes, cymbals and such are so incredibly blunted as to make you do a double take in certain passages of music. But for the £35 I spent on them, I can look past this flaw.

Soundstage and Imaging
This ain’t no three-blob affair. Imaging is actually decent on the Koss Porta Pro. Every note and instrument feels as though it has it’s own defined space in the room, but said room does feel kind of small. I’m talking about the soundstage of course; it’s relatively narrow. But the focussed imaging is one of the first merits I noticed about the Porta Pro, as its leaps and bounds ahead of any other headphone I’ve heard at this price point outside of the Koss ecosystem.

Detail
Due to how close your eardrum is to the drivers, you get an impressive level of attack and decay on the edges of notes, which is perceivable as detail. Music sounds sharp and each note well defined, except maybe in the treble region which as mentioned before, is quite recessed and therefore muffled.

On very busy sections of certain tracks however, the driver seemingly has too much to do and gets a little lost, losing out a bit on resolution. Totally excusable at sub-£50, however.

Overall Verdict
The Koss Porta Pro deserves to be merited on its sound quality alone, not just on its absurdly low price tag. But at such an affordable cost this is an easy recommendation for any audiophile, from the beginner to the serious collector. Prepare to be surprised, in a good way.

Rating: 7/10

See the full article here: https://jamesfiorucci.wordpress.com/2023/12/26/simple-audio-review-audio-technica-ath-r70x/

I’ve been in the audiophile space for a number of years now, and become all the more aware of the inconsistencies prevalent in this hobby. The “objectivist vs. subjectivist” argument will rage on beyond the end of time itself, for example.

I for one am not a big fan of the Harman target, with it’s emphasised mid-bass and treble frequencies. Everyone has their own preferences, and it’s been a long and admittedly costly journey to find my preferred sound.

With a few minor caveats, the Audio-Technica ATH-R70x is EXACTLY what I want in a headphone.

This pair is kindly on loan from a fellow local collector, and I’m dreading the day I have to return these back to them, such is the profound impact they have had on me.

If I had to describe the R70x simply, it’s a HD600 on steroids. Let’s explore some of the reasons why in this Simple Audio Review.

Comfort and Build
Can’t talk about the build of the R70x without mentioning it’s so-called “3D wing support” headband system.

In essence it’s just like a regular elasticated suspension strap but with the middle part missing. It makes up for this with a stiffer elastic and decent clamp force to keep the headphones in place. Despite having a small skull, the R70x don’t move around on my head at all, even during a particularly passionate head-banging tirade!

Since there’s no headband in contact with the top of the scalp, I find these headphones very comfortable for long listening sessions. Add to that their vanishingly low weight (210g exc. cable), this is of the few cans that don’t give me any sort of fatigue beyond a couple of hours of use.

It’s not all good news though. My ears are smaller than average, but the inner diameter of the earpad are so small that my lower lobe and upper helix touch the pad. While there’s no pain, this minor gripe prevents the R70x from truly disappearing on my head.

Furthermore, some vertical articulation of the earcups would have been nice, as this would make it slightly easier to get a proper seal. I do manage it after a bit of fiddling and minor positional adjustment, it’s just a bit frustrating sometimes.

In terms of build quality, I think the R70x is a no-nonsense, sturdy piece of kit. Nothing fancy, just clever use of metal and high-quality plastics that assures you they won’t break from a fall from your desk. Which can’t be said for all headphones!

I’m not a fan of the almost-proprietary, twist-lock, dual-2.5mm connectors though. You have limited options to change out the cable, and the 3-metre length isn’t really practical for the majority of use cases either.

Sound
At around the $300 price category, the Audio-Technica pits itself up against the legendary benchmark, the Sennheiser HD600. And the similarities don’t stop there by any means.

The HD600 is revered by the headphone community as a reference point and default recommendation for those looking for a neutral sound signature at a relatively affordable price point. Well, the R70x has a very similar frequency response, with a few tiny differences here and there.

But, in my opinion, the R70x one-ups the HD600 is several key departments, so much so that I consider it an upgrade with a few small caveats. I know not everyone agrees with that sentiment, however I rarely find myself reaching for the HD600 since I got my hands on the R70x. As I said earlier, I’m not looking forward to the day I have to give them back to my friend.

Let’s look into the sound in more detail, starting with bass.

Bass
I’ll be making various comparisons with the HD600 in this review, as I think many will want to know how the R70x stacks up against it. When it comes to bass, it’s not much of a stretch to say that the R70x simply beats the HD600.

First of all, it extends a fair bit deeper than the Sennheiser. While there is a bit of roll-off in the deep subbass, the lower frequencies pack a pleasant level of authority that, despite demanding attention, don’t bleed into the mids whatsoever.

Good macrodynamics certainly aids in giving the bass ample amount of impact as well as texture. It’s no bass monster, but the lower frequencies are the star of the show from my personal listening experience.

Mids
The midrange of the R70x takes a very slight step back in the mix compared to the HD600, but it’s still certainly what one would call a “mid-forward” tuning.

I find that certain instruments and vocals in particular are a touch less smooth, but in no way intrusive. It’s something you’d only notice when really analysing certain tracks and swapping between it and the HD600, which is what I was doing when I made this observation.

At the end of the day, it’s a matter of preference. Want the singer’s voice and guitar riffs to tickle your ears and take centre stage? Perhaps the HD600 is better for you. But I think the R70x is the better all-rounder, and will work harmoniously with the vast majority of genres thanks to its comparatively pulled back midrange tuning.

Treble
Treble fanatics may want to brush the R70x aside. Not that it’s bad, it’s a little dark in terms of it’s frequency response.

The mid-treble is noticeably recessed, albeit not overly so. It’s a non-issue apart from in songs that are heavy in cymbals, where the harmony can sound blunted and lacking in outright volume.

The treble picks up in its upper reaches, giving tracks plenty of air and brilliance. But once again, the treble is not quite as silky smooth as it is on the HD600, which can actually be either a blessing or a curse depending on how intense you want your music to be.

Imaging and Soundstage
OK, so this is where the Audio-Technica really amazed me. Used to the “three-blob” imaging capabilities of the venerable HD600, the R70x precise localisation of sound was a truly eye-opening moment in my audiophile journey.

Not only does it fill out the soundscape between your ears, it also pinpoints sounds up and down the ear, which admittedly was a new sensation for me.

Unfortunately the soundstage doesn’t extend far out beyond the ears. This isn’t necessarily a bad thing however, as it leads to what I like to call a “cohesive” image where every bit of space within the head stage is filled out and there are no dead zones.

As an explanatory comparison, the AKG K702, while having an impressively wide soundstage, lacked a coherent image between the dead centre and the widest reaches. This almost made it sound like different instruments were playing in different rooms, which soured the overall experience.

The R70x avoids this, and despite being not much wider-sounding than the average closed-back headphone, has precise imaging which not only makes for an immersive musical experience, but also makes the headphone perfect for gaming applications.

More Notes
With an impedance of 470 ohms, a dedicated amplifier is recommended for the Audio-Technica R70x.

I found I could get more than ample volume plugging straight into my phone and laptop, but imaging and layering abilities were hampered and soundstage was squashed in even more than it already was. Not that it’s suddenly bad, but to unlock that final 10% or so you do require an amp with adequate power.

Moving up to the Fiio E10K Olympus 2, things improved somewhat but the budget amp/DAC introduced a bit of treble peakiness that wasn’t to my liking.

Only when I plugged the R70x into my Topping DX3 Pro/A30 Pro desktop stack did the headphones truly open up to their full potential. So while these Audio-Technica cans sound great through almost any source, bear in mind they scale tremendously well with higher power amplification.

Overall Verdict
The Audio-Technica ATH-R70x has got to be one of the most underrated dynamic open-back headphones on the market. With crystal clear imaging and a near-perfect neutral sound signature, these headphones need to be in the same conversation as the Sennheiser HD600 as a benchmark in the $300 price category. A versatile all-rounder which is ideal for long listening sessions, the R70x is an easy recommendation from me, as long as you don’t have large ears and have some sort of dedicated amplification solution.

Rating: 9/10