Tubes for Everyone | Feliks Audio Echo MKII Review

Tubes for Everyone | Feliks Audio Echo MKII Review

Feliks Audio has gained a reputation for building OTL and Tube headphone amps that look amazing and sound even better. At $1099, the entry point to their lineup is the Echo MKII OTL tube amp, which has some cool vibes but a simpler design than their top of the line amps. Is Echo MKII a good starting point for audiophiles looking to make the switch from solid state to tubes – or could it even be a sort of Endgame for budget conscious listeners??

Build and Design

Echo MKII’s black metal chassis and walnut trim would look perfectly comfortable in a lineup of vintage headphone or guitar gear, but also fits in aesthetically with modern systems with classic designs. The tube complement doesn’t look as impressive as the Euforia or Envy’s larger tubes, but the 6N6P and 6N1P tubes look great when they glow up while the amp is operating.

Feliks Audio Echo MKII Review

In terms of tech specs, Echo MKII has three inputs and a preamp output on the back. On the front you have a 6.3mm headphone output, a large, smooth volume knob, and a 4-way selector to choose between the inputs and a mute mode. The output power is a max of 350mW, which doesn’t seem like “desktop” level power in solid state world, but when it comes to tubes – and  particularly OTL (Output Transformerless) amps – 350mW is pretty significant and can drive a wide range of headphones with plenty of volume.


It seems that part of the core of Feliks Audio’s sound is pushing tube amps to be as accurate and transparent as possible. While there’s an inherent warmth to the tube sound, which compared to strictly transistor based amps, Echo MKII creates a sound that’s organic while also feeling natural and neutral.

Echo MKII’s bass feels full and rich, but isn’t emphasized in the tuning and doesn’t lend itself to bloat, even with warmer sounding headphones. It can definitely deliver quite a bit of slam, and the bass is overall deep, dynamic, and well-crafted. The midrange presentation is absolutely off the charts. Echo MKII delivers a natural, organic midrange with excellent note weight.  The treble has a hint of the “tubey” euphonic harmonic distortion with a touch of smoothness, but don’t expect super smooth highs. Instead it’s surprisingly clean and transparent, with great extension.

Feliks Audio MKII Review

Changes to the volume level definitely have a higher impact on your sound with tubes than with solid state amps. Using a DAC with a preamp or a DAP gives you the opportunity to balance the two outputs and get the best performance from the tubes. Increasing the volume on the tube amp against the preamp added weight and body to the sound, really bringing out the tube character. I found the best range for the amp to be around 50-60%, so I set the amp volume there, and used the pre-amp as volume control.

We tried a number of different headphones with Echo MKII, and while OTL amps excel with dynamic drivers and high impedance headphones, they do struggle a bit with low impedance, low sensitivity planar magnetic headphones. More sensitive planars get excellent performance, but something like a HIFIMAN HE6 or Susvara is going to end up feeling a bit flabby and underwhelming. Though they struggle with lower sensitivity, OTL amps like Echo MKII excel for “hard to drive” high impedance headphones like the Sennheiser HD800S.

Audeze’s sub-$2000 line-up sounds fantastic with Echo MKII. With LCD-XC, Echo MKII seems to fill-in some of the mids and smooth out the sharpest bit of highs offering a great pairing for those who find LCD-XC to be a little too bright out of the box. And MM-500 had just a little bit of life and color breathed into it, that took it beyond its more reference sound.

Feliks Audio Echo MKII Review

For dynamic driver headphones, the Sennheiser HD650 paired with this amp might be a sort of “mid-fi endgame.” The two really bring out the best in each other, from the tonality and color to the speed and dynamics. The Meze 109 Pro was another favorite, delivering solid spatial performance with a three-dimensional soundstage and exceptional vocals. It seemed like the bass was enhanced just slightly, adding a bit more punch, and making the 109 Pro one of my favorite pairings with the Echo MKII.

Probably my overall favorite was the HIFIMAN Arya Stealth. While Echo wasn’t quite up to the task of powering the big boys at the top of HIFIMAN’s lineup, Arya and Echo MKII make a perfect pair.  The dynamics and tonal balance are amazing, and it was the second most spacious of any headphone I heard (behind the HD800S), but it added a weight to Arya’s image, filling out the sound, and also lent a more natural character to the highs, enhancing Arya’s timbre.

Comparison: Burson Soloist 3X Performance

What better comparison could there be but the timeless battle between tubes and solid state? For that we bring in the Burson Soloist 3X Performance: an incredible, powerful solid state amp that redefined the $1000 price point when it was released. So what’s the best pick, or should you just get both?

Both amps reside just on the opposite sides of neutral from each other, with Echo MKII leaning towards a slightly more relaxed sound, while Soloist leans into a more forward aggressive one. I should note that I mostly used the volume control bypass mode on the Soloist, which I find to deliver clearer, more transparent highs in making my impressions. With the volume bypass, Soloist gains a bit more treble extension and provides a higher degree of transparency.

Feliks Audio Echo MKII Review Burson Soloist 3X Performance

The Soloist’s main advantages are the high level of power and the stronger treble extension. Soloist handles both ends of the “hard to drive” family with ease: high impedance headphones like the HD800S sound great, as do HIFIMAN Susvara level low sensitivity planars. The soundstage tends to feel a bit larger as well.

For Echo you gain that touch of smoothness in the highs, as well as a slightly elevated midbass and hint of warmth. While I generally find the Soloist to sound natural, in comparison to Echo MKII it sounds a bit cold. While the treble on headphones like HD800S and Arya sound clean and crisp with the Soloist, there’s a more organic, natural element to the presentation with Echo.

They’re just distinct enough that the choice here is more about genre and preference than one having a clear advantage over the other – even with the same headphones. For example, with the 109 Pro, Echo MKII adds a more engaging feeling, with a touch of warmth that really excels with jazz – giving extra weight to upright bass, thump in the kick drum, and cutting the slightest bit of edge off the top. But pairing 109 Pro with the Soloist, you get a more spacious delivery and more precise imaging that lends itself to classical and orchestral music. In the Soloist vs Echo battle, the longer you listen, the more you might say “maybe I should buy both of them?”

The Bottom Line

Echo MKII is the perfect introduction to Feliks Audio’s line of beautifully crafted tube amps. The attention to detail and craftsmanship is evident in the build and look of the product, and the sound provides a clean, transparent presentation, with just the right helping of classic tube sound. Whether you see it as the entry point into Feliks Audio’s legendary lineup, or as an Endgame setup for the more budget conscious with headphones like the 109 Pro or HD650, Echo MKII won’t disappoint.