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SPL Phonitor One Review

Hello fellow audio enthusiasts! Whether it's for work or fun, we are always searching for ways to upgrade our sound and playback references. It's essential to be able to drive various types of headphones and always achieve a clear, detailed soundstage when listening to and referencing music.

A professional amplifier is an essential component for achieving a consistent listening experience. The Phonitor One has been fulfilling its high-fidelity mission for four years in many homes, desks, and studios worldwide. It provides users with professional sound, monitoring versatility, and all at a reasonable cost compared to top-end gear on the market.

Overview and Specifications

SPL Phonitor One Headphone Audiophile Amplifier Front

The Phonitor Series One, also available as the 'One d' with stand-alone DAC functions, offers a balance between SPL pro audio features and desktop setups. This compact device contains the professional core found in top-level production devices such as the Phonitor 3, 2 and X.

SPL Phonitor One Headphone Amplifier Rear

The unit has two line inputs, a balanced TRS and an unbalanced RCA connection at the rear. The front panel has a TRS headphones output, a volume analog controller, an input switch, and a crossfeed matrix controller. The input impedances are 20Ω (balanced) and 47Ω (unbalanced), while the source output is 20Ω, providing a wide range of connectivity options.

It's worth pointing out the choice of high quality components. The preamplification stage of the amplifier is really efficient, providing a great quality-to-price ratio. The class AB output stage, along with the attention given to the power supply circuitry, make the SPL amplifier a fantastic and practical choice.

If you're interested in the technical specifications for the Phonitor, you can find them at the end of the article.


The best feature of this amplifier is the Phonitor Matrix technology. This is an analogue circuit that provides the solution to the typical "super stereo" effect produced by headphones. The matrix allows the left and right signals to cross as they are reproduced by a pair of speakers, creating a natural and pleasing stereo image. Perfect for extended listening, long mixing sessions and effective translation across different playback systems.

In the case of the Phonitor One, the only Matrix technology control available is the Crossfeed Amount, with the Angle set to a fixed 30° (studio speaker opening angle). The knob on the front panel controls the amount of crossfeed from Off to Max.

This allows you to choose how much of the left and right signals will flow into each other. Finally, to ensure correct stereo imaging, a -1dB cut is applied to the centre sources in the stereo image when the matrix is active. This cut helps to manage the crossfeed action and further enhances the perception of stereo detail without overwhelming the frequency response.

Setup integration is seamless, with two input options and a choice of connectors making it easy to integrate the Phonitor into home and studio setups. The analogue volume knob has a smooth and controlled action, giving the end user a good range of control. When it comes to volume selection, this amplifier really comes into its own, reaching surprisingly high levels even when compared to SPL's top end amplification options.

Performance & User Experience

SPL Phonitor One Headphone Amplifier and Phonitor X headphone apmplifier and monitoring controller

Setting up our balanced connection was very straightforward, while a power extension was needed to reach a power source. The power cord is really designed for compact desks.

Once the music started to flow, the amount of detail the Phonitor One was able to deliver was immediately plain. It reproduced the stereo image truly and evenly giving a great example of accuracy and definition across the frequency spectrum that is difficult to match with similar amplifiers.

The matrix function is identical to that of other Phonitor models. The ability to access the same feature in such a small unit, ¼ the weight of a Phonitor X and able to fit anywhere, makes it an excellent compromise.

With the core of SPL's larger amplifiers, it is also able to drive a wide range of headphones, consistently delivering detail and clarity. When pushed to its volume limits, the compact size begins to show its limitations, with some saturation in the upper mid-range of the spectrum.


·      Crossfeed Matrix

·      High end circuitry

·      Wide range of compatibility

·      Compact size


·      Limited to 2 input sources

·      Higher saturation over components than the bigger units

·      No 120V Technology


The Phonitor One made a really good impression. No question why it has become so popular with producers, engineers and audiophiles. It really does provide access to a full and accurate music experience without ear fatigue. For those looking for a professional upgrade to their listening setup, the Series One is a fair and valuable option.

We believe that any expression of high-end engineering must be backed by equal or greater effort. The Phonitor really comes into its own when paired with good sounding headphones, as the amplifier boost can exaggerate some of the shortcomings of some headphones design.

We were pleased to note how the Series One strives to sound as close as our Phonitor X, this series of amplifiers condenses SPL's top end gear experience and can surely play a great role in many desktop setups bringing the listening experience to instant professional fidelity grade.

It was a great pleasure to test this unit and compare it to its larger cousins. The sonic consistency delivered by this product is one of the best features of this series of amplifiers, bringing more people closer to the perfect sound experience with their headphones.   


Happy listening!

SPL Phonitor One headphone amplifier box inside 432studios control room

Technical Specifications

·       Analog inputs & outputs = 6.35 mm (1/4") TRS Jack (balanced), RCA

·       Input gain (max.) = +22.5 dBu

·       Input impedance Line In 2 (balanced) = 20 kΩ

·       Common mode rejection=   < 60 dB

·       Input impedance Line In 1 (unbalanced) = 47 kΩ

·       Headphones Output = 6.35 mm (1/4") TRS Jack

·       Wiring

·       Tip = Left, Ring = Right,

·       Sleeve = GND

·       Source impedance = 20 Ω

·       Frequency range (-3 dB) = 10 Hz - 200 kHz

·       Noise (A-weighted, 600 Ω) = -97 dBu

·       THD + N (0 dBu, 10 Hz – 22 kHz, 600 Ω) = 0,002 %

·       THD + N (0 dBu, 10 Hz – 22 kHz, 32 Ω) = 0,013 %

·       Max output power (600 Ω) = 2 x 190 mW

·       Max output power (250 Ω) = 2 x 330 mW

·       Max output power (47 Ω) = 2 x 400 mW

·       Fade-out attenuation (600 Ω) = -99 dB

·       Crosstalk (1 kHz, 600 Ω) = -75 dB

Internal Power Supply

·       Operating voltage for analog audio = +/- 17 V

·       Operating voltage for headphone amplifier = +/- 19 V

·       Operating voltage for relays = +12 V


External Power Supply

·       AC/DC switching adapter = Mean Well GE18/12-SC

·       DC plug = (+) pin 2.1mm; (-) outside ring 5.5mm

·       Input = 100 - 240 V AC; 50 - 60 Hz; 0.7 A

·       Output = 12 V DC; 1.5 A


Dimensions & Weight

·       W x H x D (width x height incl. feet x depth) =210 x 49,6 x 220 mm / 8,23 x 1,95 x 8,66 inch

·       Unit weight = 1,45 kg / 3,2 lb

·       Shipping weight (incl. packaging) = 2 kg / 4,4 lb

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