Phonitor One d

The audiophile headphone amplifier

with innovative Phonitor Matrix, 32-bit DA-converter and outstanding sound quality.

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Monitoring in highest sound quality with up to 32 bit and 768 kHz.

Create perfect mixes on headphones – thanks to the Phonitor Matrix.

number one in sound

For us the sound is always in the foreground. When it sounds good, we like to listen. To get such a sound, you need experience and technical finesse. We have incorporated both into the Series One.

The design of the amplification stages

The preamplifier stage

Two Burr-Brown OPA 2134 SoundPlus™ operational amplifiers provide the pre-amplification. These are specially designed for audiophile circuits and are characterized by extremely low noise and minimal distortion of only 0.00008%.
Thanks to a true FET stage, the OPA 2134 achieves a slew rate of 20V/µs, making it a high-speed operational amplifier. This has an immediate positive effect on the liveliness of the playback.
In addition, low capacitance film capacitors are installed in the signal path as bypass capacitors of the coupling capacitors, which ensures a more precise transmission of the high-frequency signal components.
The excellent Panasonic ‘Electric Double Layer’ gold electrolytic capacitors are used as coupling capacitors. They offer the highest storage capacity of all capacitor technologies.

The headphone output stage

Weak sound on headphones?
Not enough power?

Not here. Phonitor One d delivers a full headphone sound – and that up to really loud.

The output stage of the headphone amplifier is designed as a push-pull amplifier in class AB mode. The bipolar transistors share the amplification of the positive and negative half-waves, which produces a higher gain and a higher output voltage than in Class A operation, where only one transistor amplifies both half-waves.

The output stage transistors are thermally coupled and thus run particularly coherently, which contributes to a consistent and stable sound image.

The power supply has a buffer circuit with low source resistance, ensuring generous current reserves even when operating low-impedance headphones.

Siegel_EC_PAM_2021_SPL Phonitor One d
Siegel_EC_PAM_2021_SPL Phonitor One d

“With the Phonitor One d, SPL has created an excellent sounding headphone amplifier, plus equally valuable D/A converter, with integrated crossfeed Matrix at an affordable price that meets the highest sound demands.”

Professional Audio

The Revolution: Phonitor Matrix

The Phonitor Matrix is the revolution in the headphone amplifier.

It enables mixing and mastering engineers to create perfect mixes on headphones, which will translate perfectly to all types of stereo speaker systems.

With the Phonitor Matrix, you can create mixes on headphones that sound just like on speakers.

But the Phonitor Matrix is not only designed for professional use in the studio.
It also enables the hifi enthusiast to enjoy music on headphones, like if it was played back on speakers.

How is this possible?

Music is normally produced and mixed for playback on stereo speakers.

Listening on headphones is different from listening on loudspeakers. The biggest difference is the lack of crossing signals of the sound signal from the left speaker to the right ear and from the right speaker to the left ear.

These crossing signals are missing in conventional headphone listening, because there are no signals crossing from one side of the headphones to the other. This results in an unnaturally wide stereo stage and sound sources are not played back at their correct position in the stereo spectrum.

The SPL Phonitor Matrix can correct this false stereo image with an analog circuitry.

The Phonitor Matrix parameters

The two main parameters of the Phonitor Matrix are Crossfeed and Angle:

• Crossfeed determines the crossing signals of the channels.
• Angle determines the opening angle of the stereo image.

The “Crossfeed” parameter of the Phonitor One d is continuously adjustable via the crossfeed control.
The “Angle” parameter is fixed at the studio standard of 30°.

To perfect the listening experience, the level of the sound sources centered in the stereo image must be attenuated when the Phonitor Matrix is activated. The result is that not only the position of all sound sources is correctly located, but also their volume.

For the Phonitor One d, this parameter, which we call “Center” for the Phonitor Matrix, is fixed at a -1 dB cut, which is the best choice for an authentic representation of the soundstage.

During conventional listening on headphones, our brain can compensate a certain level of false playback representation – but this is very exhausting and leads to listening fatigue.

Summed up:

The SPL Phonitor Matrix corrects the false representation of the stereo sound image, which makes it much easier to find the right decisions for mixing and mastering engineers. The hifi enthusiast can experience the music, like it was originally mixed and recorded.

So nothing stands in the way of a successful and long mixing session on headphones.

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Everything you need to know about the Phonitor Matrix
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Everything you need to hear about the Phonitor Matrix

“the SPL Phonitor One d is a device that can make the essential difference for audiophile listening in the living room as well as for working in a recording studio.”


Free choice – three stereo inputs

The Phonitor One d offers two analog stereo inputs (TRS and RCA) and one digital (USB).

A computer, tablet or smartphone can preferably be connected via USB.

Input devices with an analog output signal, such as CD players, mixers, synthesizers or an analog tape machine/tape deck, can be connected balanced (TRS jacks) or unbalanced (RCA) at the analog line inputs.

The best is just good enough – 32-bit DA-converter

Of course, no compromises were made with the converter chip either. For example, the Phonitor One d also uses the premium AK4490, 32-bit DAC with AKM’s Velvet Sound® – just like our bigger DACs.

This technology makes the finest details audible thanks to its low-distortion architecture.

It supports sampling frequencies up to 768 kHz PCM (16x CD resolution) and DSD (Direct Stream Digital) playback up to DSD4 or DSD256 (11.2 MHz) resolution.

The Phonitor One d automatically synchronizes to the sampling rate applied to the USB input. No further settings on the device are necessary.

A great connection

The USB connection is Class Compliant. This means that all Mac computers and iOS devices like iPads and iPhones can use the full performance of the DA-converter without driver installation.

iOS devices require the “Apple camera adapter”.

For Windows, a driver is only required if higher sampling rates are desired. The driver is available for download at the bottom of this page.

“With the Phonitor One d, SPL has created an amazing device when it comes to bringing the quality of studio technology to the homes of every music lover at an affordable price. The noble appearance and the high manufacturing quality make the decision for the Phonitor One d easy.”


Line Out

Phonitor One d is not only a headphone amplifier but also a stand-alone DAC! The signal selected in the input section is output unchanged at the line output “Line Out”.

The line output has unity gain, which is a normal, unregulated output level – it is independent of the volume control for the headphone amplifier.

Thus, the Phonitor One d can also be used as a state-of-the-art DA-converter, which recommends it for a series of other tasks.

This signal can be routed to a monitor controller, for example.

Or multiple users can listen in via additional headphone amplifier (e.g. Phonitor One) connected to the Line Out.

The Phonitor One d can also be easily looped into a monitoring chain without the need for another output at the playback source.

But you can also record the signal analog or send it to a mixer for further processing.

There are no limits to creativity here.

Perfectly adjusted

At a regular listening volume, the volume control should be in the one o’clock position.

This gives you an ideal control path for listening quieter and louder.

In order to obtain an optimal control range even with very powerful headphones, the output level of the headphone amplifier can be attenuated by activating the -10 dB DIP switch.

Power Supply

Good sound always starts with the power supply. This is where you lay the foundation for the performance of the entire device. Although we “only” supply a 12 V plug-in power supply unit, the secondary power supply inside generates a voltage level of +/-17 Volts for the analog audio sections with which professional levels of up to +22.5 dB can be achieved!

An elaborate low-drop operating voltage regulation provides more “juice” and regulates cleanly even when the maximum operation voltage is reached. The Phonitor One d delivers full power when used with the included 1.5 A power supply. Just switch it on and enjoy the great sound. The ON-switch puts the Phonitor One d into operation.

“I’ve always been happy with my headphones and and my headphone amp attached to the audio interface, but since I’ve heard, tried and tested the combination of a high quality headphone amp with high quality headphones, I have to say there are worlds apart from what I’ve used before and what I was able to test here today.”

Muso Talk

Number One in Sound

With the Series One – just as with all other SPL devices – we develop not only according to plan, but also by ear from the very beginning.

Many important components are installed on the circuit boards using Through-hole technology. This way we can ensure that we can use the best sounding components.

Home is where the heart is

That’s why we manufacture all devices in our own production facility in Niederkrüchten on the Lower Rhine, Germany.


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SPL Phonitor One d – Don't Mix On Headphones....Without This!
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Phonitor One @ proaudio TV
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Phonitor One d @ Headphone Show
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Phonitor One d @ musotalk
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Phonitor One d @ Delamar


Professional Audio
Age Of Audio
Age Of Audio

Other Series One products


Comparison Chart


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

Input gain (max.)
+22.5 dBu
Input impedance Line In 2 (balanced)
Common mode rejection
< 60 dB
Input impedance Line In 1 (unbalanced)
Output gain (max.)
+22 dBu
Output impedance Line Out (balanced)
150 Ω
Frequency range (-3dB)
10 Hz - 200 kHz
Noise (A-weighted, 0 dBu, 600 Ω load)
- 99 dB
THD + N (0 dBu, 10 Hz – 22 kHz, 600 Ω)
0.002 %
THD + N (0 dBu, 10 Hz – 22 kHz, 32 Ω)
0.013 %
Crosstalk (1 kHz)
< 75 dB
Dynamic range
121.5 dB

USB, 32-Bit DA

USB (B), PCM sample rates
44.1/48/88.2/96/176.4/192/352.8/384/705.6/768 kHz
USB (B), DSD over PCM (DoP), sample rates
2.8 (DSD64), 5,6 (DSD128), 11.2 (DSD256) MHz
0 dBFS calibrated to
15 dBu
Noise (A-weighted, 44.1/48 kHz sample rate)
-113 dBFS
THD + N (-1 dBFS, 10 Hz – 22 kHz)
0,0012 %
Dynamic range (44,1/48 kHz sample rate)
113 dB

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

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

Betriebsspannung für analoge Audio-Elektronik
+/- 17 V
Betriebsspannung für Kopfhörerendstufe
+/- 19 V
Betriebsspannung für Relais
+12 V
Betriebsspannungen für Digitalsektion
+3.3 V, +5 V

External Power Supply

AC/DC switching adaptor
Mean Well GE18/12-SC
DC plug
(+) pin 2.1mm; (-) outside ring 5.5mm
100 - 240 V AC; 50 - 60 Hz; 0.7 A
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 lbs
Shipping weight (incl. packaging)
2 kg
4.4 lbs

Reference: 0 dBu = 0,775V. All specifications are subject to change without notice.

The Drivers

Mac OS & iOS

No driver installation required for Mac or iOS devices (class compliant).

iOS devices must be connected using the Apple camera adapter.


To operate with a higher than the standard sample rate this driver installation is required.


Windows 10 up to 21H2, 11 up to 22H2
(32/64 bit)

Previous Version

Windows 10 up to 21H2, 11 up to 22H2
(32/64 bit)

Legacy Driver
(last version with Windows 7/8/8.1 support)

Windows 7/8/8.1 and Windows 10 up to (2009/20H2)
(32/64 bit)


Calculation of VAT (value added tax)

All prices are displayed by default including the VAT of your country.

If your country cannot be determined via geolocation and you are not logged in as a user with the billing address of your country, the prices are displayed including the VAT of Germany (19%).

What does it actually mean …

In Stock!

The product is in stock in our warehouse in Niederkrüchten, Germany, and will be shipped the same or next working day.

We process the orders after receipt of the order and update the stock in the online shop regularly. If the product is no longer available at short notice due to high order volume, you naturally have the right to withdraw from the purchase (see Right of Withdrawal).

In any case, you will receive an e-mail with details of the delivery and the estimated delivery time.

Available soon!

The product is not in stock in our warehouse in Niederkrüchten, Germany. Usually it will be available again within 5 working days.

In any case, you will receive an e-mail with the details of the delivery and the estimated delivery time.

Of course you have the right to withdraw from your purchase (see Right of Withdrawal).

Currently unavailable.

This product is currently sold out and unavailable.

Was bedeutet eigentlich …

Auf Lager!

Das Produkt ist in unserem Lager Niederkrüchten vorrätig und wird noch am selben oder nächsten Werktag versendet.

Wir arbeiten die Bestellungen nach Bestelleingang ab und aktualisieren den Bestand im Online-Shop regelmäßig. Falls das Produkt wegen hohem Bestellaufkommens kurzfristig nicht mehr verfügbar ist, hast du selbstverständlich das Recht, vom Kauf zurückzutreten (siehe Widerrufbelehrung).

In jeden Fall erhältst du eine E-Mail mit den Einzelheiten der Lieferung und der voraussichtlichen Lieferzeit.

Bald verfügbar!

Das Produkt ist in unserem Lager Niederkrüchten nicht vorrätig. Gewöhnlich ist es innerhalb von 5 Werktagen wieder verfügbar.

Auf jeden Fall erhältst du eine E-Mail mit den Einzelheiten der Lieferung und der voraussichtlichen Lieferzeit.

Selbstverständlich hast du das Recht, vom Kauf zurückzutreten (siehe Widerrufbelehrung).

Zur Zeit nicht verfügbar.

Dieses Produkt ist derzeit ausverkauft und nicht verfügbar.


Due to Covid19 there are no events scheduled at this time.


Aufgrund von Covid19 sind derzeit keine Events geplant.