Hereby I present you my first product review (read: essay) on this forum, covering my newly acquired OTL tube amp, the Feliks Audio Euforia. I’m posting it a bit sooner than I thought I’d be able to, but I ended up spending just a little bit more time with it than I normally listen to music on a daily basis, I’ve done roughly 50 hours of listening and about 10-15 more hours of letting the tubes burn in without listening. By now I’ve reached a point where I feel like what I’ve written down is true to my experience. Of course this is just my own experience, I have no objective intentions behind anything stated in this review.
The Euforia is what I ended up purchasing after having auditioned a bunch of different amplifiers and a whole lot of online research. A few noteworthy (non-hybrid) tube amplifiers I’ve auditioned include Feliks Audio Elise, AudioValve Solaris and Fezz Audio Omega Lupi, and a few more of which I don’t recall the names or didn’t have names. There was one was from Pathos Audio.
Now that I have it at home and spent some quality time with it, let’s get into the review!
Build, features & I/O
The Euforia, like all Feliks amps, is hand-crafted with supreme care and engineering expertise. At 6kg (13lb), this is a heavy piece of equipment, especially for how small it is in size. Ignoring the tubes themselves, it feels like the unit is built to survive a nuclear blast. The build quality is nothing shy of exemplary. Nothing about this amp looks or feels cheap or compromised in whatever way.
It comes with matched pairs of driver- and power tubes. The driver tubes are 2x PsVane CV-181 Mk2 “Silver” or “Gold (+€100)”, and the power tubes are 2x 6N13S NOS. Installing the tubes is very straight-forward, although the force required to securely fit them into place is a bit uneasy. Pushing them in with some gentle wiggling did the trick.
I personally have no clue whether the Gold tubes are even worth it over the Silver ones, but I don’t think I’d be the only one just going for the Gold upgrade purely for the peace of mind. You could also order it without tubes for an extra -€100 on the cost. I can’t give any educated advice on what the smart move is there though. Input on this is welcome though. It seems that it is generally agreed that going for the Gold upgrade is the way to go.
To go through all of the inputs, outputs, knobs and buttons;
On the front-panel there is only the volume knob and a single-ended 6.35mm headphone output. The volume knob has a satisfying amount of feedback/resistance to it, and has no wiggle to it at all. It feels about as high-end as volume knobs get.
On the rear-panel, we find a pair of RCA line-inputs and a pair of RCA pre-outs, which again are very sturdy and feel like they can take a proper beating without anything breaking.
My only point of “criticism” here is that the pre-outs only output a signal when the amp is powered on, and are always volume-controlled. I would’ve preferred it if the RCA outputs would function as a fixed line-output or just an RCA passthrough when powered off. I’m no engineer myself though, so I don’t know if this is a reasonable thing to ask for or not.
Lastly we find the PSU socket and 2 on/off switches on the back. 1 of the switches being simply the power on/off switch, the other being a switch for toggling a unique analog Crossfeed implementation on or off.
This analog Crossfeed implementation feels like it’s doing quite a bit more than just blending L/R channels together. The frequency response seems to also change quite substantially to a warmer, more relaxed presentation with a recession in the upper mids and treble. Macro-dynamics are also pulled back, so the intense experience now becomes a very relaxed upfront presentation, perhaps a bit subdued.
The resulting presentation still provides an enjoyable listening experience, and doesn’t sound objectionable to me with both the Empyrean and HD 660S at all. If I’m tired or trying to focus on work, I turn Crossfeed on and pull the volume down to an average background listening volume level. In my opinion, this is a perfect use case for it, and I really appreciate having this option available. You’re getting 2 completely different presentations from 1 and the same amp, which you can freely switch between on demand. The icing on the cake would’ve been to have that button placed on the front-panel, but this is hardly even an issue.
Aesthetics & Ergonomics
It takes up only slightly more desk space than a THX 789, no fancy bells & whistles to be found on the housing, no odd/unique shapes or anything. It’s just compact and discreet looking. How they placed the tubes + the aesthetics of the tubes themselves in combination with the simple and discreet housing of the amp itself, it puts the spotlight on the tubes more than the amp itself. It’s just very satisfying to look at. Those big, shiny bulbs just have a very confident aesthetic appeal to them. It just looks like it sounds good. (spoiler) And it sounds as good as it looks, and that’s just such an oddly satisfying experience overall. It’s like what you see and what you hear is aligned.
While the volume knob feels great and is placed in a great spot too, there only is a slim gap on the outer ring of the volume knob to tell the knob’s position by. Just a decently sized dot or line in a contrasting color as a position indicator would’ve been nice.
General operation, burn-in & best practices
Since this is a tube amp, there are some best practices to handling it to ensure that it performs optimally. I’ve been in contact with Feliks Audio to get some advice on this for the Euforia specifically, and I feel this is worth sharing too.
The tubes do need some time to burn-in and reach their optimal working conditions. Feliks Audio suggests 50 hours of using the amp normally at medium volume levels just listening to music to music as the right way to go about this. They don’t recommend to leave it on overnight. For minimizing stress on any of the components, they suggest that the amp should ideally not be powered on for longer than 8 hours consecutively, and suggest powering it off to let it cool down for around 1 hour before powering it on again. So I intend to follow that advice and keep it in mind as a good practice.
After powering the amp on, it takes around 15 minutes for the tubes to reach their ideal operational temperatures. I have not noticed any noteworthy changes in sound over extended periods of time.
As the tubes were burning in during those first 50 hours, I did notice a change in sound for sure, but this wasn’t a significant change by any means. Very early on there was the occasional slight bit of audible crackling, but this didn’t happen constantly and was hardly bothersome and disappeared after the first day. Other things I noticed is that as time went on, the bass got a little bit more liquid, and the treble lost some of the upper edge to it, smoothing out a bit more. It didn’t completely change the sound of course, and even during the first 50 hours it already sounded just like the amp I remembered from when I auditioned it. My impressions haven’t really changed much during this time.
For powering it on/off, the only precaution I was suggested to take is to turn down the volume before powering it on/off or (un)plugging headphones. They have implemented safeguards for any loud pops/bursts, and just following this simple advice has kept me free from any such unpleasantness.
What I continued to notice, especially with my more sensitive HD 660S, is a faint low frequency humming that was unaffected by the position of the volume knob. I think this is that 50Hz mains noise, and this might be at fault of my outlets.
(WILL UPDATE WITH A SOLUTION LATER)
Other than that, the noise floor of this amp is completely absent within the usable volume knob range with the headphones I’ve tried with it, and it only starts to reach audible levels when turning the volume up way beyond listenable volume levels.
Using the preamp outputs of the Euforia with my speaker amp and THX 789 worked perfectly fine. It sounds ultra clean and transparent, not as tube-like as the headphone output and free from distortion until at least 12 o’clock on the volume wheel. It seems like 12 o’clock is where you reach around 2 Vrms coming out of the pre-outs judging completely by ear, and going beyond there you start pushing it into heavy distortion territory.
In the manual, Feliks Audio included the following information for optional tube-rolling:
Euforia is originally equipped with high quality tubes.
Stock driver tubes are 6SN7 power tubes are 6N13S.
Tubes can be changed by the user, to the following:
- Driver tubes: 6N8S, CV181, ECC32, 5692, 6F8G
- Power tubes:6080, 5998, 6N5P, 6N5S, ECC230, 7236, CV2523
I have not bothered with any tube rolling yet, and don’t think it’s necessary at all, but maybe I’ll try it eventually. Nice to see that Feliks Audio is supportive of their customers rolling different tubes on it.
Communication & support
Since I’ve had some email contact with Lukasz from Feliks Audio with a number of questions, I think people would appreciate hearing that Lukasz has been responsive, very friendly and helpful, answered my questions in an easily digestible and no-nonsense manner. From my experience being in contact with Lukasz, I feel that aside from them being very passionate, knowledgeable and proud of their own products (rightfully so), they understand that customer satisfaction is just as important as the quality of their products themselves. This should be the standard in the high-end audio industry in my opinion, but unfortunately there are too many companies where you just don’t get the level of support we as highly paying customers deserve to get. Thankfully Feliks Audio gets the big fat thumbs up here from me, and this makes it that much easier to recommend their products to others as well.
Now to the sound… Where do I even begin? There truly is a lot to be said about the sound of the Euforia, but how do you explain “magic” in human language? That’s the challenge, and I’ll do my best to write down everything that has struck me during my listening time with the Euforia. I won’t keep it short and concise, and there will be no TL;DR. I’ve tried but failed to summarize the Euforia’s sound in a way that captures the true nature of its sound, and I’d like to not give any misinformation about this beautiful champ of an amp.
For context, the gear used during the writing of this review:
- DAC of choice: Schiit Bifrost 2
- Reference amp: THX AAA 789, all descriptions can be considered as “compared to the 789”
- Headphones used: Meze Empyrean & Sennheiser HD 660S
I’ve made a playlist with a fraction of the music I’ve been listening to, that have one way or another stood out to me when heard with the Euforia. This is not a playlist of “my favorite tracks of all time” or “my top picks for gear evaluations”, but a somewhat random selection of different things I’ve come across during my time listening. Just to provide you guys with some context behind the music I listened to during the time before posting this review.
Any changes in FR are very modest and it stays close enough to sounding neutral. Specs claim that the FR is consistent within a 3 dB margin, and as far as I am able to hear this seems to be correct. I’m not sure if changes in FR manifest themselves equally between my headphones, so I’ll describe them individually. I must admit, precisely evaluating such minor changes in FR is one of the more difficult things about evaluating sound in headphones for me.
With the Empyrean, it seems that the Euforia pulls back the Empyrean’s bass-tilted FR a bit to the more neutral side, resulting in a slightly more “correct” sounding Empyrean.
Some people might wonder; But what about that planar bass?!
Probably one of the biggest weaknesses of most tube amps, keeping up with the current demand of low impedance planars with their bass extending flat down to sometimes even under 10Hz.
With the Euforia, I’ll admit it doesn’t exactly match the bass performance of a proper solid-state amp from a purely technical standpoint. But it is also highly track-dependent and most often requires pushing the volume to unsafe volume levels before the Euforia starts losing control of the Empyrean’s bass.
Distortion in the bass region is definitely noticeable on normal listening volume levels, but is in my opinion not objectionable. There is a bit more grunt to the bass, comes across as more authoritative, but remains well-rounded and liquid in texture, and does not increase any sense of muddiness or bass bleed except for the very occasional (usually badly produced) bass-heavy track. Compared to the 789, the bass loses some transparency in return for some grunt and sounding more liquid. While logic would suggest that this would mean some detail will be lost, I can’t say that I feel like certain details are subdued by this. So perhaps this results in a slight loss of detail, it just isn’t apparent to me at all.
With the HD 660S, bass and treble extension both seem to be brought up a bit. It still sounds mid-forward, but less aggressively so. Sub bass is brought up and sounds surprisingly clean and weighty. Treble sounds crisp, very clear yet non-aggressive. While I’d normally use a Harman-based PEQ with my HD 660S, the Euforia has eliminated the urge for me to use EQ with my HD 660S, although when I do use that EQ setting right now it still sounds like the sound signature I’ve been used to, but a turbocharged version of it. The benefit with the Euforia is that the bass not only sounds more authoritative, but also sounds more liquid and dynamic.
With the Empyrean, the soundstage the Euforia presents is expansive, increasing in both width and depth, stretching more towards you and away from you. Layering is more 3-dimensional and true to life. It feels like being pulled into the soundstage, providing a sensation closer to feeling like you’re there with the music, and having less of a spectators position. This makes for a more immersive and engaging experience.
With the HD 660S, the soundstage is also expanded in both width and depth, but it feels like it expands more than it does with the Empyrean. There is a similar improvement in layering/3-dimensionality. Instead of being pulled into the soundstage, the normally in-your-face center-image of the HD 660S is gently moved further back to a more comfortable position. This results in a soundstage that is more similar to how higher end headphones present their soundstage, and this is a very welcome improvement for the HD 660S.
With the Empyrean, the “dynamic ceiling” it tends to have on amps like the 789, doesn’t seem to be present anymore with the Euforia. Kickdrums, snares, cymbals, anything that comes with impact hits with more physical weight and authority. Each hit is clearly distinct, powerful, but without ever sounding unpleasantly aggressive.
With the HD 660S, much of the same applies. Bass hits harder and with more weight, percussions come through more clearly.
With both headphones, what the Euforia does with macro-dynamics strikes me a bit like fireworks. It makes you look up and be in awe with the powerful sound of the explosions, and the bright, playful color patterns. This contributes to the experience being more exciting, intense and dynamic, yet neither of my headphones become any more fatiguing as a result of this.
I’ve noticed that the Euforia shows a better ability for subtle sounds to distinctly move through the soundstage freely. Background subtleties are presented more clearly and their micro-dynamic behavior is easier to follow. Small, distant subtleties don’t fade out as much, and are presented in their full colors without sounding louder or being pulled closer. This applies to both my Empyrean and HD 660S equally.
Tone density & timbre
On both headphones, the sound has less of a “texture” to it, sounding smoother and more on the ”wet” side. Each sound has a greater sense of body, colors seem more naturally saturated and enriched without overdoing it. The edges of each sound are more apparent, and this enhances the sense of size and space between different sounds.
While this is likely greatly influenced by a lot of things I described above, the perception of detail and image-clarity is greatly increased. Subtleties are more apparent, 3-dimensionality is greatly increased, acoustic reverberations feel more true to life and movement within the music comes through more clearly.
Although increased intensity would normally go hand-in-hand with being more fatiguing as well, I don’t experience any fatigue at all. Thankfully if fatigue is a concern, there is the Crossfeed button which instantly subdues the sound to where any fatigue will be greatly lessened.
Conclusions & value
This amp has been the purchase of a lifetime for me. After my search for the headphones I wanted the most (which resulted in the Meze Empyrean, in case you jumped straight to the conclusions without reading ), I set out to find the amp I wanted the most as well, and after having it for some time now I can safely say that I feel like I made the right choice. There might be something better on the market, but I don’t specifically want the best, I just wanted to find an amp that rocks my world. The Euforia does exactly that, and against what I expected it made me fall in love with my HD 660S all over again.
This is not “just a headphone amplifier”. This is an Experience Amplifier™. Hand-crafted by a passionate family of Polish engineers who justifiably take pride in their world-class engineering expertise, and they know damn well how to make their amps sound exceptionally good. The name fits the product perfectly, as the sound really does manage to make me feel somewhat euphoric when listening to music. You get much more than your money’s worth, this is a legitimate top of the line amplifier, and for €2099 I absolutely consider this to be a fantastic value.
The Euforia should be considered by those who have already explored the high-end headphone market and found themselves at least one pair of headphones they’re truly satisfied with. I don’t know exactly what headphones it will pair well with, but it seems like bad pairings for this amp are few and far between. From low impedance planars to high impedance dynamics, it has the power for almost anything, and a sound that just gives you more of everything you love about your music and headphones without being so different or colored that it really changes the music or headphones in their core sound signature.
Needless to say, Feliks Audio’s Euforia earns a very strong recommendation from me. I hope my review managed to capture what this amp means to me, and for whom this might be an equally fantastic purchase.
Feel free to ask me anything you’d like to know about this amplifier, or if anything needs further elaboration or reconsideration.