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SPL Audio Phonitor One d Audiophile Headphone Amp/DAC



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Product Details

↓ Details provided by SPL Audio

Phonitor One d

The Audiophile Headphone Amplifier

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


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 Power Amplifier

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.

The Revolution​

in the headphone amplifier is the Phonitor Matrix, with adjustable crossfeed, thanks to which you can create mixes with headphones that sound the same on speakers.

The Phonitor Matrix in its largest expansion stage has three setting parameters: Crossfeed, Speaker Angle and Center Level. 

In the Phonitor One d, the center level is preset to -1 dB and the speaker angle to 30°. These are the most commonly used values.

The crossfeed function determines the crosstalk of the channels, the so-called interaural level difference. The intensity of the crossfeed is fully variable. 

At the beginning of the control path the function is not in the audio path. It is only switched on by adding it via relay (hysteresis circuit). The audio signal therefore does not pass through the crossfeed stage if this is not desired.

Three Stereo Inputs

Two analog stereo inputs and one digital USB input can be connected to Phonitor One d. The computer, tablet or phone are preferably connected via USB.

Other players such as a CD player, mixer, synthesizer or an analog tape machine / tape deck can be connected to the analog line inputs either balanced (TRS jacks) or unbalanced (RCA).

32-Bit DA-Converter

The converter chip used is the Premium AK4490, a new generation of premium 32-bit DACs equipped with AKM’s Velvet Sound®. This technology makes the finest details audible thanks to its low-distortion architecture.

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

This qualifies the Phonitor One d for the currently highest resolution audio playback.

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

iOS devices require the camera adapter. For Windows a driver is required, which you can download at the bottom of this page.

Line Out

The selected input signal is output unchanged at the line out. This allows Phonitor One d to be looped between devices without “losing” an output connection.

If, for example, several people are to listen in via headphones, a headphone amplifier can simply be connected to the Line Out.

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

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.

The 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. Only use the 12 V plug-in power supply unit within the scope of delivery. The ON-switch puts the Phonitor One d into operation.

Phonitor Comparison

Phonitor xe Phonitor x Phonitor se Phonitor 2 Phonitor One Phonitor One d
Phonitor Matrix
Crossfeed 6 Values 6 Values 2 Values 6 Values Potentiometer Potentiometer
Speaker Angle 22° / 30° / 40° / 55° 22° / 30° / 40° / 55° 30° 15° / 22° / 30° / 40° / 55° / 75° 30° 30°
Center Level
Matrix on/off
Remote Control* Volume
Laterality Control Super fine Balance
Stereo/Mono Playback Modes
Solo L/R & Phase Monitoring functions
VU Meters
ø 36mm illuminated VUs
0dBVU Calibration (+4dBu) 0 / 6 / 12 dB 0 / 10 dB 0 / 6 / 12 dB
Headphone Outputs
Front & Rear Outputs
Additional Output Boost +22 dB +12 / +22 dB +12 dB +6 / +12 dB
1/4” Jack
1/4” Jack Output power (1 kHz, 1 % THD, 600 Ω) 2 x 2.7 W 2 x 2.7 W 2 x 2.7 W 2 x 2.7 W 2 x 190 mW 2 x 190 mW
1/4” Jack Output power (1 kHz, 1 % THD, 250 Ω) 2 x 5 W 2 x 5 W 2 x 5 W 2 x 5 W 2 x 330 mW 2 x 330 mW
1/4” Jack Output power (1 kHz, 1 % THD, 32 Ω) 2 x 1 W 2 x 1 W 2 x 1 W 2 x 1 W 2 x 400 mW 2 x 400 mW
4-pin XLR (Balanced)
4-pin XLR Output power (1 kHz, 1 % THD, 600 Ω) 2 x 8 W 2 x 8 W
4-pin XLR Output power (1 kHz, 1 % THD, 250 Ω) 2 x 3.5 W 2 x 3.5 W
4-pin XLR Output power (1 kHz, 1 % THD, 32 Ω) 2 x 0.7 W 2 x 0.7 W
Line Outputs
XLR (Balanced)
1/4” Jack (Balanced)
RCA (Unbalanced)
Speaker Output Selector
Line Inputs
XLR (Balanced) ● (2x)
1/4” Jack (Balanced)
RCA (Unbalanced)
RCA -10dBV to 0dBu Boost
DA converter (optional)
Model DAC768 DAC768xs DAC768xs DAC768xs
DLP120 (dual low pass filter)
Bit/Max SR kHz 32/768 32/768 32/768 32/768
DSD (max) 256 (11.2MHz) 256 (11.2MHz) 256 (11.2MHz) 256 (11.2MHz)
Coaxial (RCA)
Optical (Toslink)
Housing WxHxD (incl. Feet) 278 x 100 x 300mm 278 x 100 x 300mm 278 x 57 x 300mm 278 x 100 x 300mm 210 x 49.6 x 220mm 210 x 49.6 x 220mm
11” x 4" x 11.81” 11” x 4" x 11.81” 11” x 2.24" x 11.81” 11” x 4" x 11.81” 8.23” x 1.95” x 8.66” 8.23” x 1.95” x 8.66”
Weight 5.1kg/11.24lbs 4.3 kg/9.5 lbs 3.1kg; 6.8 lbs 4.3kg; 9.5 lbs 1.2kg; 2,65 lbs 1.45kg; 3.2 lbs
*Units learn any IR remote. RC is not part of the scope of delivery.


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 Speaker Out (balanced)
150 Ω
Output impedance Line Out (unbalanced)
75 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 AD/DA

USB (B), PCM sample rates
44.1/48/88.2/96/176.4/192/352.8/384/705.6/768 kHz kHz
USB (B), DSD over PCM (DoP), sample rates
2.8 (DSD64), 5.6 (DSD128), 11.2 (DSD256) MHz 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 dBFS

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 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 %
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 and LEDs
+12 V
Operating voltage for digital audio
+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.

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