SPL Phonitor se Headphone Amplifier

Welcome

Thank you for purchasing the Phonitor se. The Phonitor se is SPL's entry-level model into the world of VOLTAIR headphone amplifiers. It shares the same audio signal amplification as its predecessors, the Phonitor x and Phonitor xe, offering a comparable sound experience. The DAC768xs is available as an optional upgrade.

VOLTAIR technology, also known as SPL 120V Rail Technology within the Professional Fidelity series, makes the Phonitor se an outstanding device. It excels in dynamic range, signal-to-noise ratio, and headroom, delivering an exceptional sound experience characterized by serenity, transparency, and realism.

Rear view of the SPL Phonitor se, illustrating the Mains Switch, Mains Voltage selector, Analog Audio Input, Digital Audio Inputs (Coax, Optical, USB), and serial number plate.

Bottom view of the SPL Phonitor se, showing the unit's underside with four feet and a small DIP switch.

Content Overview

This manual covers the following topics:

• Getting Started
• Front View
• Rear View
• Bottom View & DIP Switches
• VOLTAIR – 120V Rail Technology
• Comparisons
• Phonitor Matrix
• Source Selection
• Headphone Output
• DIP Switch Settings
• Specifications (Inputs, Outputs, Voltages, Power, Dimensions, Weight)
• Important Notes
• Declaration of CE Conformity

Getting Started

Please read and follow all instructions and security advice provided in the Quickstart guide, which is included with the delivery. The Quickstart guide can also be downloaded.

Navigation within the manual is facilitated by dedicated buttons:

• [Table of Contents]: Access the table of contents.
• [Front View]: Navigate to the front view description.
• [Rear View]: Navigate to the rear view description.
• [Bottom View]: Navigate to the bottom view description.
• [Previous]: Return to the previous section.

Front View

The front panel of the Phonitor se features the following controls and indicators:

1. Standby: Power button to turn the unit on or off.
2. Headphone Output: Standard 1/4" (6.35 mm) stereo jack for connecting headphones.
3. Crossfeed C1/Off/C2: Selects the crossfeed level, influencing the stereo image.
4. Input Selection: Switch to choose between Analog and Digital inputs.
5. Volume: Rotary knob for adjusting the output volume.
6. Digital Source: Selects the digital input type (USB, Coaxial, Optical) when the input is set to Digital.
7. Power LED: Indicates the operational status of the unit.

Rear View

The rear panel provides connections and power management:

1. Mains Switch: Main power switch for the unit.
2. Mains Voltage: Selector for the mains voltage (115 V AC / 230 V AC).
3. Analog Audio Input: RCA connectors for analog audio sources.
4. Digital Audio Inputs: Connectors for digital audio sources, including Coaxial (RCA), Optical (TOSLINK), and USB (Type B). These are available if the optional DAC768xs is installed.

The rear panel also displays voltage information, fuse details (230V: T 315 mA, 115V: T 630 mA), voltage selection instructions, and manufacturing information (Made in Germany).

Bottom View & DIP Switches

The underside of the Phonitor se features four feet for stability. A DIP switch is located on the bottom panel, accessible for configuration.

A close-up view of the DIP switch, showing two switches labeled '1' and '2', with the factory setting indicated.

VOLTAIR – 120V Rail Technology

VOLTAIR is the designation for SPL's 120V Rail Technology, a core component of the Professional Fidelity series. This technology processes audio signals using an exceptionally high +/-60V DC voltage. This is double the voltage of discrete operational amplifiers and four times that of semiconductor operational amplifiers.

VOLTAIR Technology delivers outstanding technical and sonic performance, particularly in terms of dynamic range and headroom. Sonically, it excels at reproducing fine details and provides a relaxed, natural listening experience. It is important to note that this is an internal audio processing voltage and should not be confused with the external mains voltage (115V or 230V AC).

Bar chart comparing operating voltages: +/-15 Volt (30V) versus +/-60 Volt (120V).

Bar chart comparing dynamic range: OPA 134@30V (124.2 dB) versus SPL-OP@120V (141.4 dB).

Decibel (dB) scales represent exponential increases. A 3 dB increase signifies doubling acoustic power, +6 dB doubles sound pressure level, and +10 dB doubles perceived loudness.

In terms of volume, maximum level, and dynamic range, VOLTAIR Technology offers performance approximately 12 dB higher than common components. THD measurements show an improvement of over 8 dB compared to the TL071 at 30V, translating to over 130% improvement in sound pressure level. The typical operating level for audio equipment is +/-15 volts.

Bar chart comparing maximum audio levels: OPA 134@30V (21.5 dBu) versus SPL-OP@120V (33.2 dBu).

Bar chart comparing THD&N: TL 071@30V (-106 dB) versus SPL-OP@120V (-114.2 dB).

Phonitor Matrix

Basics of Stereo Listening

When listening to speakers, sound originating from the right is perceived by both the right (red line) and left (green line) ears. This perception involves a time delay, lower level, and reduced frequency range for the sound reaching the opposite ear. This occurs because the signal travels a distance of approximately 340 meters per second, and the path from the right speaker to the left ear is longer than to the right ear. The sound is also quieter and its frequency range is limited due to partial reflection and absorption by the head.

Illustration depicting sound waves from right and left loudspeakers reaching a listener's ears, highlighting the differences in arrival time and level.

The brain determines sound direction by processing these time delays (interaural time difference) and level differences (interaural level difference).

Stereo Listening with a Traditional Headphone Preamplifier

With a traditional headphone amplifier, each ear primarily receives the signal intended for it (right ear for right signal, left ear for left signal). This results in a missing delayed and quieter signal from the opposite side. This unnatural sound can be fatiguing and stressful for the brain, as it constantly tries to orient the sound source. This 'super-stereo-effect' can also lead to exaggerated stereo width, making instruments appear positioned too far outside the intended stereo field.

The Phonitor Matrix is designed to correct these unnatural effects.

Illustration showing a listener wearing headphones, with signals from left and right channels depicted, emphasizing the lack of cross-channel information in traditional setups.

How the Phonitor Matrix Works

The Phonitor Matrix creates a speaker-like listening experience on headphones by calculating time and level differences, along with their specific frequency responses, to accurately replicate speaker playback. By setting these differences to match real loudspeaker placement, the brain can correctly identify sound direction, providing a natural, speaker-like experience.

Instruments are positioned correctly within the stereo image as intended during mixing. Compared to traditional headphone amplifiers, it offers superior conditions for minimizing listening fatigue.

In Detail: Angle

The Phonitor se features a fixed 30° speaker angle placement, representing a standard speaker setup. This angle is used to create the interaural level and time differences through analog filter networks.

Diagram illustrating a listener positioned between two speakers, with each speaker angled at 30° relative to the listener's center.

Crossfeed

Crossfeed defines the interaural level difference. The two available crossfeed settings (C1 and C2) approximate the influences of room size, reflection, and absorption characteristics on the sound.

Line graph showing frequency-corrected level difference at Crossfeed C1 and 30° Angle, with red representing the right channel and green the left channel.

Line graph showing frequency-corrected time difference at Crossfeed C1 and 30° Angle, with red representing the right channel and green the left channel.

The interaural level and time differences are frequency-corrected to account for the non-linear way the head reflects and absorbs sound.

Phonitor Matrix Presets

The Phonitor se offers two presets for the Phonitor Matrix: C1 and C2. The speaker angle is fixed at 30°.

Setting C1 provides less crossfeed, resulting in a lower time difference compared to setting C2.

Illustration of the Crossfeed selector with options C1, Off, and C2.

Source Selection

Up to four audio sources can be connected to the Phonitor se.

Connect your analog source to the RCA Input (labeled as '10' in diagrams).

With the optional DA converter (DAC768xs) installed, the analog input is expanded to include USB, coaxial, and optical digital stereo inputs (labeled as '11' in diagrams).

• Use the INPUT switch (4) to select between analog or digital audio sources.
• When the input is set to Digital, use the DIGITAL switch (6) to select the specific digital source (USB, coaxial, or optical).

Illustration of the INPUT switch with 'Digital' and 'Analog' positions.

Illustration of digital input options: Coax, USB, Optic.

Headphone Output

The Phonitor se provides up to 2 x 5 watts of output power at the Headphone Output (labeled as '2' in diagrams). This power capability allows it to drive even demanding headphones, such as magnetostats or electrostats, effortlessly.

To protect the headphone amplifier stage and ensure long-term performance, please observe the following:

• Turn down the VOLUME before swapping headphones.
• Never insert a mono jack plug into the front panel stereo jack.
• Ensure that the headphone stereo jack is fully inserted.
• If using a 3.5 mm to 1/4" (6.35 mm) adapter, confirm it is securely screwed on or fully plugged in.

DIP Switch

The DIP switch (12) located on the bottom panel allows for adjustments to the headphone output level.

Level Increase of the Headphone Output

Using DIP switch 1 can increase the headphone output level, providing more power for demanding headphones.

• DIP switch 1: ON – The headphone output is boosted by +12 dB.
• DIP switch 2: Not applicable (n/a).

Specifications

Inputs

RCA Input:

• Unbalanced
• Impedance: 20 kohms
• Max. Input level: +32.5 dBu

Digital Inputs (Optional DAC 768xs) / Sample Rates:

• Coaxial SPDIF (RCA) - PCM sample rates (kHz): 44.1, 48, 88.2, 96, 176.4, 192
• Optical TOSLINK (F06) – PCM sample rates (kHz): 44.1, 48, 88.2, 96 / with Glass fibre <1m: 176.4/192 kHz
• USB (B), PCM sample rates: 44.1, 48, 88.2, 96, 176.4, 192, 352.8, 384, 705.6, 768
• USB (B), DSD over PCM (DoP), sample rates: 2.8 (DSD64), 5.6 (DSD128), 11.2 (DSD256) MHz

Outputs

Standard Headphone Output:

Warning: Never connect a mono jack cable to the standard headphone output (front panel stereo jack). Ensure the stereo jack is fully inserted; otherwise, a short circuit could damage the headphone amplifier.

• Connector: 6.35 mm TRS
• Pin wiring: Tip = Left, Ring = Right, Sleeve = GND
• Source impedance: 0.18 ohm
• Damping factor (40 Ω): 180
• Frequency range (-3 dB): 10 Hz to 300 kHz
• Crosstalk (1 kHz): -90 dB
• THD & N (10 Hz – 22 kHz, 0 dBu): 0.00091%
• Noise (A-weighted): -103 dB
• Output power (1 kHz, 1% THD, 600 Ω): 2 x 2.7 W
• Output power (1 kHz, 1% THD, 300 Ω): 2 x 5 W
• Output power (1 kHz, 1% THD, 32 Ω): 2 x 1 W
• Dynamic range: 135.5 dB

Internal Operating Voltages

• Operating voltage for analog audio: +/- 60 V
• Operating voltage for relays and LEDs: 12 V
• Operating voltage for DAC768xs: +7 V, +3.3 V

Power Supply

• Mains voltage (switchable): 230 V AC / 50 Hz or 115 V AC / 60 Hz
• Fuses: 230 V: T 315 mA; 115 V: T 630 mA
• Power consumption: max 30 VA
• Stand-by power consumption: 0.3 W

Illustration of the mains power input socket with voltage selector and fuse holder.

Dimensions (incl. feet)

• (WxHxD) 11 x 2.24 x 13 inches (278 x 57 x 330 mm)

Weight

• Unit only: 6.17 lbs (2.8 kg)
• Shipping: 8.6 lbs (3.9 kg)

Important Notes

Version: 1.0 – 08/2020

Developer: Bastian Neu

This manual describes the product but provides no guarantee for specific characteristics or successful results. All information corresponds to the technical status at the time of product delivery by SPL electronics GmbH, unless stated otherwise. The design and circuitry are subject to continuous development and improvement. Technical specifications are subject to change.

© 2020 SPL electronics GmbH. This document is the property of SPL and may not be copied or reproduced in any manner, in part or fully, without prior authorization by SPL. Sound Performance Lab (SPL) continuously strives to improve its products and reserves the right to modify the product described in this manual at any time without prior notice. SPL and the SPL Logo are registered trademarks of SPL electronics GmbH. All company names and product names in this manual are the trademarks or registered trademarks of their respective companies.

Declaration of CE Conformity

The construction of this unit is in compliance with the standards and regulations of the European Community.