The SPL Diamond is a high-end digital-to-analog converter (DAC) and stereo preamplifier designed for audiophiles who primarily listen to music from digital sources. Manufactured in Germany by SPL (Sound Performance Lab), this model stands out for its exclusive VOLTAiR technology, which operates at a working voltage of ±60V (120V in total), far exceeding market standards. This unique design achieves exceptional performance in terms of dynamics and sound fidelity, delivering a natural and detailed listening experience even at low volumes.
VOLTAiR technology is the Diamond’s major innovation. Unlike conventional operational amplifiers that typically operate at ±15V, the Diamond’s circuits run at ±60V. This fundamental difference significantly increases the dynamic range, from approximately 124 dB for traditional circuits to over 141 dB.
This high operating voltage is not just a technical feat: it translates into an audible improvement in the signal-to-noise ratio and more faithful sound reproduction. Components always operate within their optimal range, reducing distortion and providing fatigue-free listening, even during long sessions.
The Diamond also features the DLP120 (Dual Low-Pass) system, a sophisticated dual low-pass filter that processes PCM and DSD signals differently. This tailored approach ensures that each type of signal is optimally filtered before being converted into an analog signal.
The Diamond stands out for its exceptional versatility with six stereo digital inputs. The device includes a USB-B input, an AES/EBU (XLR) input, two coaxial S/PDIF (RCA) inputs, and two optical TOSLINK inputs. This variety of options allows multiple digital sources to be connected simultaneously without the need to constantly unplug and replug devices.
On the output side, the Diamond offers two stereo analog outputs: a pair of balanced XLR connectors and a pair of unbalanced RCA connectors. A particularly practical feature is the ability to independently configure each output as fixed or variable via a DIP switch located on the back of the device. This functionality allows the Diamond to be used as a simple DAC with a fixed-level output to feed an amplifier already equipped with volume control, or as a full preamplifier with volume control to directly drive a power amplifier.
At the heart of the Diamond is the AKM AK4490 Velvet Sound DAC, a component renowned for its musicality and precision. This DAC supports PCM formats up to 32-bit/768 kHz (16 times the resolution of a standard CD) as well as DSD formats up to DSD256 (Quad Rate DSD).
The Diamond automatically detects the sampling rate and resolution of the source, displaying this information on its elegant LED dot-matrix screen. For demanding users, the device also features a Word Clock input for external synchronization, ensuring perfect timing accuracy during conversion.
True to SPL’s characteristic aesthetic, the Diamond boasts an elegant and minimalist design available in three finishes: black, silver, and red. Its compact chassis (278 mm × 57 mm × 300 mm) integrates easily into any audio system.
The front panel features an intuitive interface with a large, precisely machined solid aluminum volume knob. This knob is mechanically coupled to an Alps RK27 “Big Blue” potentiometer, renowned for its smooth and precise rotation, often described as “a spoon in honey.” This analog volume control design ensures optimal resolution even at low volumes, unlike digital systems that may lose precision under such conditions.
The LED dot-matrix screen clearly displays the selected input, clock source, and detected sampling rate, providing all essential information at a glance.
The Diamond is entirely manufactured in Niederkrüchten, North Rhine-Westphalia, Germany. SPL uses through-hole mounting technology for its circuits, allowing the use of the highest-performing components in terms of sound quality rather than being limited to surface-mount compatible components.
This attention to detail is reflected in its exceptional audio performance: an extended frequency response from 10 Hz to 300 kHz, total harmonic distortion of only 0.001%, and an impressive dynamic range of 135 dB. These technical specifications translate into sound reproduction with remarkable clarity and precision, offering a wide and detailed soundstage.
The Diamond is positioned as a more affordable alternative to SPL’s Director Mk2 model while retaining the core of its sound quality. Unlike some models in the range, such as the Phonitor, the Diamond does not include an integrated headphone amplifier, focusing exclusively on its DAC and preamplifier functions.
This specialization allows it to excel in its field, delivering exceptional performance for audiophiles who already have a separate headphone amplifier or who primarily focus on listening through speakers.
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VOLTAiR technology uses proprietary operational amplifiers operating at ±60V (120V in total), four times higher than traditional circuits. This high voltage enables a superior dynamic range (over 141 dB compared to approximately 124 dB) and a better signal-to-noise ratio. In practical terms, this results in more detailed, natural, and less fatiguing sound, even during long listening sessions.
Yes, absolutely. The Diamond features a DIP switch on the back that allows each output (XLR and RCA) to be independently configured as fixed or variable. In fixed mode, the volume control is bypassed, transforming the Diamond into a simple DAC with a constant output level, ideal for use with an integrated amplifier or an external preamplifier.
Yes, the Diamond has a dedicated Word Clock input that allows the device to synchronize with a high-precision external clock. This feature is particularly useful in professional studios or complex audio systems where multiple digital devices need to be perfectly synchronized to avoid jitter (timing fluctuations).
For Mac and iOS users, the Diamond works as a plug-and-play device without requiring any additional drivers. For Windows users, a specific driver is necessary and can be downloaded from SPL’s official website. This driver ensures optimal compatibility and provides access to all the advanced features of the DAC.
The Diamond does not directly integrate network or streaming functionalities. However, it can easily be incorporated into an existing streaming system by connecting it to a network player, a computer, or any other device with a compatible digital output (USB, optical, coaxial, or AES/EBU).
The main advantage of the Diamond compared to its competitors is its exclusive VOLTAiR technology, which offers an exceptional dynamic range. While many high-end DACs focus on sophisticated digital components, SPL has also chosen to optimize the analog section with this proprietary technology. The result is a particularly natural and detailed sound that stands out for its musicality rather than clinical precision.
Vincent
Excellent DAC, I recommend it, especially on the AES output; USB is a bit bright. Go for it without hesitation…
Comment from January 07, 2026 — Experience from December 27, 2025
