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Review - Feliks Audio Echo MkII

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Also available on YouTube in Spanish: Acho Reviews YouTube


The Feliks Audio Echo Mk2 has been sent to me by Feliks Audio directly on an open ended loan, allowing me to hold on to the amplifier long term and use it as a test amplifier as well as create this review.

Feliks Audio have not requested anything specific, in fact, they haven't even given me a time schedule for publishing this review (which is a good thing seeing that I have already had the amp in my possession for over a month) nor any specific links to publish.

Even though they haven't specifically asked me to, I not only feel it is fair to include links, I also think that anyone who is interested in this, or any of the Feliks Audio line up, should know where to go. Therefore, I am going to leave a little more than my usual single, non-affilate, links…

To visit Feliks Audio directly, you can visit their website here:

Or you can reach out to them via Facebook:

If you are based in Spain, you can reach out to the official dealers, Supersonido, via Facebook:​​​ or Instagram:

Or visit their web:

Finally, if you are based in North America, you can reach out to

Again, none of the above are affiliate links but they are links to 3 companies who will be more than willing to help you on your tube amp quest 😉


Before I begin, I want to share a little backstory here. Many will consider this as my usual rambling, you have been warned, but that is why I include separate sections in my reviews (and timestamps in my videos) 😁

Some time ago, I was looking into experimenting in the headphone tube amp world. At the time, the Bottlehead Crack was an amplifier that kept being recommended, however, the BC is only available as a DIY kit or you can pay to have it built by another person. While I do like building things (I have built plenty of stuff for my bass rig), I had to be honest with myself and knowing that it would end up sitting in a box, unbuilt, for a very long time, I decided to look at other options.

Looking into other options, I came across the original Echo Mk1, with good reviews and available for a price that was about the same as the BC + Shipping + Import Costs (which soon add up here in Europe), ready built by a Polish company called Feliks Audio. As I was searching around for more info, the Echo Mk2 was announced, offering upgrades over the original Echo, at a price that was still very reasonable for a tube amp from a well regarded builder, so I started to look into it more.

I reached out to Feliks Audio, asking if there was any way I could arrange to demo the amplifier and possibly review it at the same time. I received an answer from Lukazs, the owner of Feliks Audio, who was very pleasant and put me in touch with Supersonido, the official spanish dealers of Feliks Audio. Supersonido were also very pleasant and although they couldn’t send me a demo to try at the time, due to limited stock (remember that all these units are hand built), they offered to let me visit their store(s) and spend time with the Echo whenever I wanted. Unfortunately, they (Supersonido) are located in Barcelona and Bilbao, whereas I am in Murcia, meaning a 1500km (minimum) round trip. Such a distance to spend only a few hours with the amplifier was a long trip, so we decided that it would wait until they either had a unit they could send me to try out, or whenever I got a chance to be near their store.

Time passed (over a year) and when I visited Munich High End in May this year, Feliks Audio had a nice stand and listening room set up. I did some quick listening to a few of their models on the show floor, including the new Envy, although show conditions are not great. However, at lunch that day, a few people (including Resolve, DMS and Golden Sound, amongst others) all mentioned that I must visit the Feliks Audio listening room, where they had the Envy paired with the Hifiman Susvara.

As the Susvara was one of the headphones that I was most interested in finally hearing at the show (I had been listening to it paired with the EF1000 earlier in the day), I decided to follow their advice and head over to the Feliks room, and I am so glad I did!

I was lucky to find the room empty of people and I sat down to listen to the Susvara driven by the Feliks Audio Envy… all I can say is that it is the best headphone setup I have ever experienced to date, by a long way!

Why am I rambling on about this? Well, while listening to the Envy, Lukazs Feliks arrived in the room and we got talking. I mentioned that I had been interested in the Echo and the discussions we had in the past via email, which concluded with him saying that he would send me a unit on loan to try out at home with my own gear. Obviously this is something that made me very excited, especially after just hearing a Feliks+Hifiman combination, so some months later, here we are, with the Feliks Audio Echo Mk2 that has been providing me with some great music for the last month or so.

As this seems to be reading more as a life blog than a review, let’s move on!


Ok, so we are finally going to talk about the amplifier, starting off with the presentation as always.

The amplifier is rather large (although it is rather compact by many other tube amplifier standards) and comes well packaged in a simple brown cardboard box. Inside of the box we get the amplifier, 4 tubes in individual boxes which are numbered, an IEC lead and the expected documentation and user manuals etc.

As the tubes are numbered, the user manual shows which number goes where in the amplifier, something that I feel is a very good idea. I do believe that the Echo is mostly aimed at those who are starting out in the tube amp world, although we will get to the performance soon, so things like a step by step guide on how to set it up, the needed burn in time for the tubes, etc. is all handy to have and makes a first tube experience a little less stressful.

So, all in all, the presentation is nothing spectacular but it includes everything that is needed and the way it is packed and protected means that there will be no issues in transport unless something goes very very wrong!

Build and aesthetics…

Starting off with the build quality, it is great. I haven’t opened the unit up to see the inside but if it is anything like the outside (and the internal photos I have seen of other Feliks builds), then there should be no issues due to QC (something that I certainly wouldn’t guarantee if I had built a BC 😁).

The outside is completely made of metal, except for the two wooden sides, with a nice feeling volume knob and selector on the front, along with quality connectors on the back. I really cannot spot any issues with build quality based on the outside of the amp.

As far as aesthetics, there are some really amazing tube amplifiers out there that look absolutely stunning (the Feliks Audio Envy being one of them), even if aesthetics are a totally personal choice. The Echo goes for a more simple look, yet still manages to look aesthetically pleasing (at least to my eyes). It may not be as extravagant as other options but it is still something that people ask about when they see it in my system. The truth is that tubes attract the eye and the basic yet elegant looks of the Echo make the tubes the center of attention, along with the round transformer that sits toward the back of the unit.

The looks of the Echo may not be something that I would drool over but they are still something that I like and would choose over many other options.

I really cannot fault the build or the aesthetics of this amplifier.


This is going to be the shortest section of this (long) review, as the functionality is very simple.

On the front left we have a 6.35mm headphone output, a large (and very nice) volume knob in the center, with a round selector switch at the right hand side. The selector switch allows us to choose between the 3 different inputs on the back of the unit, or mute the unit, something that I find very handy.

On the back of the Echo we find 3 sets of RCA inputs, an RCA output, the power connection and, my only negative, the power switch.

Yes, as much as I complain about power switches on the back of units, my current setup includes 3 pieces of equipment that all have them on the back. I will once more say that I much prefer them on the front but, as my current setup proves, there are other things far more important to me.

My personal use case…

Before getting to how this amplifier sounds, I will explain briefly how I am (and have been) using this amplifier. I already mentioned the main part of this in my recent review of the Hifiman EF400 but in this case there are a couple more things going on.

As the Echo Mk2 has three inputs (all unbalanced), I have been using them as follows:

Input 1 - To this input I am running a Raspberry Pi4 with RopieeeXL, via USB, to the Hifiman EF400 and then from the Ef400 to the Echo Mk2. This is my main “enjoy the music” listening set up and is the one I will be most commenting on in the sound section.

Input 2 - Here I am feeding in my main chain, which is multiple sources via USB, Coaxial and Optical into an SU-8 v2, which then feeds a THX789 and from the loop through (which is completely passive in the case of the THX789) into the Echo Mk2. I also have various other ways of routing to this input but I am not going to go into that today.

Input 3 - Here I am feeding a Denon Pro CD/Multimedia player directly into the Echo, which allows me to play from any number of sources (BT, SD, USB, CD etc.).

As I just said, I will be focusing on input 1 (EF400 > Echo), as it is the one I enjoy the most but I do have ways of routing almost anything I feel like to input 2 and have been testing all kinds of things.

The preamp output of the Echo is running to the Asgard 3, which is something I will comment on also, if this doesn’t become too long of a ramble!


Where do I start?

Let me first point out that I did burn in the tubes of the Echo for about 100 hours before listening to it (except for a quick listen to make sure it worked), so I can’t really comment on how much the sound changed during the burn in period but my guess is that quite a lot, as with any tube amplifier.

Since then, I have probably racked up another 100 hours listening time. I would really liked to have spent even more time before publishing this review but as it is summer and the temps are between 40ºC and 50ºC every day, so you can imagine how hard it is to sit down with a hot tube amplifier and over ear headphones! But… that gives me an excuse to do a follow up review when it cools down a bit 😉

I have also been using almost anything I have had on hand with the Echo, getting a feel for how things react, and how the Echo reacts, with each set. This includes planars, dynamics and plenty of IEMs. I obviously can’t list my findings with every pair that I have plugged into the echo, so I am going to stick with giving my general impressions, along with some that I find stand out above the rest.

I am going to start with a few experiences with Hifiman planar headphones. Now, it has been said many times that tube amps, at least OTL tube amps, don’t work well with low impedance headphones, which most (almost all?) planar headphones are. Even the manual of the Echo says for headphones >80 Ohm impedance. Well, I guess that, as with everything in the audio world, it is all down to personal tastes and the music listened to, along with each headphone on a case by case basis.

I have found that the Echo does lose a little definition in the lower end with the planars I have on hand, yet it is not necessarily bad. In fact, some of my most enjoyable headphones sessions have been with my favourite acoustic music running EF400>Echo II>Planars. I just found that it gave an overall smoothness to instruments and vocals that just isn’t there when using a SS amp. However, I did find that certain headphones gave better results than others when listening to the same tracks, even if the models have very similar specs.

Hifiman Ananda 

With the Ananda, I got the feeling that it lost some of the “in your face” detail presentation that I feel makes the Ananda special. It lost some of the low end definition and while it didn’t exactly become bloated, it did not separate those details as well as others.

Hifiman Edition XS

I found that the Edition XS performed much better than the Ananda in this regard. Powered by solid state amplifiers, I find that the Edition XS and the Ananda sound so similar that they are almost interchangeable, yet with the Echo, I found that there was a clear difference between the two, with the Edition XS getting some of the smoothness from the tubes but not losing as much definition as the Ananda.

Hifiman Arya v2

The Arya V2 I also found to lose out when plugged into the Echo in comparison to direct from the EF400. I found that the mids and lows sort of blended together more, again losing some of their definition and detail, while the upper mids and higher ranges sort of kept their presence, this pushed the higher frequencies a little too far forwards for my tastes. The Arya V2 also lost some of the huge open soundstage that it is famous for.

Hifiman Arya v3

Moving to the Arya V3 (with the Stealth Magnets), which is probably my favourite headphone out of the collection I have here, this reacted totally different to the V2. There was no loss of definition or detail, with music taking just the right amount of “flavour” to be one of my favourite listening experiences to date (obviously not counting the Felks Audio Envy + Susvara!). This is a combination that I just kept (and keep) coming back to over and over again. It is not a combination that I would choose to listen to EDM but that is something that I rarely listen to on my home system anyway. With acoustic guitars and vocals, I find that the combination just fills out the soundstage in a way that everything is blended together without ever feeling like there is a loss of definition. In fact, I found the soundstage to actually be much better laid out on the V3 than the V2 with this Echo in play.

Hifiman HE1000se

The last planar I am going to mention is the HE1000se, my other headphone of choice together with the Arya V3. This is another combination that I found suffers with the same issues that the Arya V2 does, making the upper ranges too present for my enjoyment. With certain male vocals it does work well but it does not have the “magic” that the Arya V3 does with the Echo.

Hifiman Planars in general 

In general, it seems that the versions with Stealth Magnets perform better with the Echo than the others. With the Arya v3 and Edition XS, both Stealth Magnet versions, performing great with the Echo, wheras the Arya v2, Ananda and HE1000se, all without Stealth Magnets, not performing as well.

I think that is enough as far as planars, I have tried a few more but I don’t want to have to divide this review into episodes!

Sennheiser HD6XX

To enter the dynamic driver world, let’s start with a classic, the HD6XX. If anyone has been reading or watching my reviews for long enough, they will know that I have a love/hate relationship with the HD6XX, loving it one day and hating it the next on the exact same set up. With the Echo in the equation, that love/hate has disappeared. It has been said many times how well the HD6XX (and 600/650) pair with tubes and all I can do is agree. 

This headphone already has mids that work very well for vocal presentation and all the Echo does is improve that. They are not quite as intimate powered from the Echo (while they still don’t have an exactly large soundstage), filling vocals out a little and making them feel lush and warm but not bloated. Listening to simple single guitar + single vocal music, I really couldn’t ask for much more enjoyment. 

I still wouldn’t class these as my favourite headphones or presentation of music, yet I could happily sit in a recliner for hours listening to my favourite acoustic music with this combo. I really do think this is the best I have heard from the HD6XX so far and I would love to get my hands on a set of HD600 to try out this same combo.

Beyerdynamic DT1990 Pro 

Another set of dynamics that are polarizing, not for me personally but for the rest of the audio world in general, are the DT1990 Pro. These are headphones that have a peak in the treble that makes a lot of people hate them. I have some foam discs in the cups that tame that treble and I find them to be enjoyable, being a very competent set of headphones. They are also the headphones that I find experiment the least changes when swapping sources, they always sound like the DT1990.

Well, the Echo is actually the first amp that I find give these headphones a new flavour, and I like the taste! With the Echo I find that they are much more relaxed, giving a vibe that is more like something I would expect from a decent set of bookshelf speakers than the studio tool that I usually find the DT1990 to be. 

I can’t say that they excel with specific tracks like some of the above mentioned combinations do but, nonetheless, I find them very pleasant and more enjoyable for relaxing listening sessions than I usually do when pairing them with other amplifiers.

Beyerdynamic Custom Studio

The last set of headphones I am going to mention is the set that basically lives on my desk for editing and other miscellaneous media consumption, the Beyerdynamic Custom Studio (not to be confused with the Custom One Pro). These are a set of headphones that are closed back and have an adjustable bass slider (that actually works well). 

I don’t usually use these for a lot of music listening (unless I need isolation, but even then I usually opt for IEMs) but I do use them for quick testing and I plugged them into the Echo to test and ended up listening for a long period of time. 

These are not overly detailed headphones but they are still decent and very balanced for a set of closed back headphones (depending on the bass slider selection). I found that these make for a very pleasurable listen on the Echo, possibly more so than the DT1990 Pro I just mentioned. I found that these work well with just about any kind of music I choose to play, without excelling at any but still being something that I am happy to listen to for hours when combined with the EF400>Echo. These are not usually a set of headphones I would pick up for listening sessions (as said, unless I need isolation) and they just live on my desk connected to a Topping stack, but I have found myself plugging them into the Echo quite a bit during the time I have been running this set up.


Before I finally get to the end of this essay of sound impressions, let me just touch briefly on IEMs. I don’t think someone running an R2R DAC into a tube amp to power IEMs is a normal occurrence, but that still doesn’t mean it can’t be done. In fact, I always enjoy running IEMs from my hybrid amps so I couldn’t not give them a whirl on the Echo.

I am not going to go into details on models as there are too many to mention, each of them reacting in different ways, but I will say that the outcome (not the sound) is similar to when I usually plug them into the P20 (a cheap hybrid amp). As the output impedance of the P20 is so high, it is a lottery as to how the IEMs react, and the Echo is much the same in this regard. However, when the right combination is found, the result is glorious!

At the moment we are hitting over 40ºC every day, which makes over ear headphones quite a chore to listen to on many occasions, and being able to plug certain IEMs into this chain and experience such a relaxing yet engrossing experience, it makes music listening so much more pleasurable.

Preamp out

I realize that I haven’t actually spoken about the preamp capabilities of the Echo MkII, which I have also found to be excellent. I have a few hybrid amps but I have to say that running the preamp out of the Echo and into the Schiit Asgard 3 is something that just takes the whole hybrid concept to another level. For the headphones that didn’t work great with the Echo (such as the Arya V2, HE1000se, etc.), I just plug them into the Asgard, adjusting the Echo output to taste and then I have the usual performance of the headphones that I expect, yet with a little sprinkling of tube on top. This really is a great chain also.

I want to try out the Echo as a preamp into my main speaker set up, which I can’t do at the moment due to the way I have the system set up, as I have a feeling that it may just give a little warmth for when I am listening to the music that benefits from it. I will report back once I have the necessary stuff to do this but I am convinced it will work well.


This is a long review and it has also taken me a long time to actually get around to putting it together. I have been listening to the Echo for over a month now (I kept expecting Feliks to reach out and ask why I hadn’t reviewed it yet) and there are a few reasons for this. There was some time spent burning in tubes, more than a hundred hours, which may not sound like a lot but when it is 40ºC, having a hot tube amp at the side of you is not the most pleasant experience and I don’t like leaving equipment on while I am not in the house. Another reason is for the exact reason I explained in the EF400 review, this set up is something that just “pulls me in to the music”, meaning it is very difficult to stop enjoying the listening and start focusing on specific things and explain them in a coherent way (if coherent is something that I ever manage to do 😁).

But here we are, I finally got around to reviewing this amplifier and I really can’t say enough good things about it. Ok, the short listening session of the Feliks Envy powering the Hifiman Susvara is probably the best headphone experience I have ever had to date but let's be fair, the Envy will cost you well over 5.000€, with the Susvara costing at least another 5.000€, then add a DAC to that and you can see we are talking anywhere between 10.000€ and 15.000€. I would love to think that I could warrant having that set up, but I can’t.

In this case, if we go with the combination that has most “wowed” me, we have the Echo coming in at around 800€, the Arya V3 at around 1600€ and the EF400 at around 650€, a total of around 3.000€ which is around half of the retail price of just the Susvara! I can’t say that this is a poor man's Envy + Susvara, as I don’t think we are talking about budget orientated stuff here at all, but i do think that the EF400 + the Echo is a set up that can easily be considered end game for many many audiophiles, for less than 1500€ in total.

The Echo performs just as well with different DACs (I have tried quite a few) but there is just something magical about it combined with the EF400 (or maybe all R2R DACs, I can’t say as I have tried any more) that makes it something that I would be more than happy to have as my only headphone set up at home. It also works really well feeding the Asgard, and even the THX789, although I much prefer the Echo + Asgard combination.

Anyway, enough rambling, I think you got the idea that I am more than praising the Echo, which I am, but if you get a chance I would strongly suggest you give it a listen for yourself and see just how great this amp is for its price!

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