Feliks Audio Echo Classic

Echo Classic Feliks Audio: OTL Tube Headphone Preamplifier

Shorten the signal path as much as possible, with no output transformer for the headphones: that is the promise of tube amplification in an OTL configuration. Here, the Polish manufacturer Feliks Audio takes the formula of its Echo mkII and streamlines it into a single-input version, with fully handcrafted production in Lubliniec, individually selected components, and a minimalist chassis dressed with solid wood side panels.

OTL amplification dedicated to headphones

The OTL (Output Transformerless) configuration removes the output transformer usually placed between the power tubes and the headphone output. The signal passes through fewer stages, and the character of the tubes reaches the listener with less interference. The trade-off is well known: an OTL amplifier delivers high voltage but more modest current. It thrives with medium- to high-impedance dynamic headphones, while low-impedance planar transducers that demand a lot of current remain below their full potential.

This approach has been part of the Feliks Audio signature since the brand’s beginnings. The Feliks family has been building tube amplifiers in its workshop in Lubliniec, Poland, since the mid-1990s. Contract manufacturing for third-party brands came before the development of in-house models such as the Echo, Elise, Euforia, and Envy ranges.

Handcrafted in Lubliniec

Everything passes through the hands of the technicians in the Polish workshop. The wiring is done point-to-point, in OCC copper, with hardwired connections. The printed circuit board plays only a minimal role, the goal being to preserve the shortest possible path between components. The power transformer is a toroidal model made to specification. On the passive components side, there are Mundorf capacitors, a German brand renowned in the hi-fi segment for the consistency of its film capacitors.

The enclosure combines a sturdy metal chassis with two solid wood side panels. The top remains open, allowing the glow of the tubes to stay visible and helping dissipate the heat produced by the four tubes in operation.

One pair of 6N1P, one pair of 6N6P

Two 6N1P tubes handle the preamplification stage, while two 6N6P tubes take care of the power stage. These Soviet-era references are prized in tube audio for their availability, reasonable price, and naturally judged sound. They are suitable for tube rolling, meaning replacement with other compatible tubes, new or NOS (New Old Stock), to alter the sound rendering according to personal taste.

Output power reaches 350 mW at 300 ohms, a modest figure on paper but consistent with the target use: medium- to high-impedance dynamic headphones do not require high current. The stated frequency response runs from 15 Hz to 45 kHz at -3 dB, total harmonic distortion stays below 0.4% at 300 ohms and 20 mW, and the signal-to-noise ratio exceeds 90 dB.

From headphone amp to hi-fi preamp

The rear panel is limited to a stereo RCA input and an RCA pre-out output, next to the 230 V power connector. On the front, there is an unbalanced 6.35 mm jack socket and a volume potentiometer. The simplification compared with the Echo mkII comes precisely from the removal of the source selector: one source at a time, connected directly.

The pre-out output broadens the role of the Echo Classic. The potentiometer then becomes the volume control for a complete hi-fi system, capable of driving a power amp or active speakers. Preamplification gain reaches 20 dB. A single unit therefore handles both headphone listening and the role of a tube preamp for the living room, with the same amplification chain.

Which headphones to pair with the Echo Classic

Feliks Audio recommends headphones with an impedance between 32 and 600 ohms, with an optimal point between 80 and 600 ohms. This upper range is the natural territory of OTL designs: a 250- or 300-ohm dynamic headphone (the Sennheiser HD 600 or HD 650 for example, or the Beyerdynamic DT series at 250/600 ohms) takes full advantage of the circuit, with controlled dynamics and a warm midrange without excess.

Low-impedance planar headphones and heavy current consumers remain compatible but do not reveal the best of the circuit: with these transducers, dynamics become more constrained and the amplifier operates less comfortably. For sensitive in-ear monitors, the 20 dB gain is high and audible hiss may be present, so that is not the natural target for the Echo Classic.

Technical specifications

Design and manufacturing

• Type: pure OTL tube amplifier (without output transformer)
• OCC copper point-to-point wiring
• Point-to-point soldering
• Toroidal transformer manufactured to specification
• Mundorf capacitors
• Handcrafted in Poland by Feliks Audio in Lubliniec
• Robust steel chassis with solid wood panels
• Open design showcasing the glow of the tubes

Tubes

• Power tubes: 2 × 6N6P
• Preamp tubes: 2 × 6N1P
• Input tubes: 2 × 6SN7 (compatible with many NOS tubes)

Audio performance

• Frequency response: 15 Hz – 45 kHz (±3 dB)
• Output power: 380 mW (up to 350 mW at 300 Ω)
• Gain (preamplification): 20 dB
• Total harmonic distortion (THD): 0.4% (300 Ω, 20 mW)
• Signal-to-noise ratio: > 90 dB
• Input impedance: 100 kΩ
• Optimal headphone impedance: 80 – 600 Ω
• Recommended headphone impedance: 32 – 600 Ω

Connectivity

• Input: 1 × stereo RCA
• Outputs: 1 × 6.35 mm headphone jack, 1 × RCA (pre-out for integrated amplifier or active speakers)
• Can be used as a hi-fi preamplifier

Power supply and dimensions

• Power supply: 230 V
• Weight: 3.5 kg
• Dimensions: 26.8 × 21.7 × 11.8 cm

Box contents

• Handcrafted tube amplifier
• 1 pair of preamp tubes
• 1 pair of power tubes
• Mains power cord
• User manual
• Warranty card