PRISM SOUND: Their Callia Preamplifier-DAC




They say .....

Designed and manufactured exclusively in the United Kingdom, the Prism Sound CALLIA USB Digital to Analogue Converter (DAC) and digital audio preamplifier is tailored for listening to music.

For the discerning listener, CALLIA is the best way to experience digital music. Coupled with high quality analogue power amplification and loudspeakers, CALLIA will deliver your music exactly as intended.

Utilising the acclaimed Prism Sound audio signal path, clock circuitry and the same ARM Cortex processor & USB platform used in Prism Sound’s professional product range, CALLIA supports both USB and S/P-DIF players.

No Compromise, Full Prism Sound Audio Quality

The design goal for CALLIA was to provide Prism Sound audio quality in a sophisticated but easy to use package for listening to music at home. CALLIA makes no compromises on audio quality. CALLIA delivers the standard of audio performance demanded by top recording professionals from 44.1kHz to 384kHz sampling or in DSD64 or DSD128.

CALLIA has the same no-compromise analogue circuitry as its professional cousins, with the same fully-balanced-throughout architecture and the same isolation barriers protecting the analogue from digital and computer interference.

CALLIA draws on Prism Sound’s years of experience in developing digital audio products, including its range of audio measurement equipment, adopted by a wide variety of clients across the audio industry from pro-audio to consumer electronics. This experience means that CALLIA is well-behaved both as a computer peripheral and an audio processor.

Reliability is vitally important in professional recording. Prism Sound has always made extensive use of precise software calibration techniques in its converters – pots and tweaks are always unreliable, so there are none.

The design team has gone to great lengths to minimise noise and interference, in particular hum. All of the analogue circuits have galvanic isolation, while the unit’s electronically balanced I/O allows it to handle common mode interference sources as well as enabling trouble-free connection to unbalanced equipment.

It is often said that THD+N figures do not always correlate well with the perception of sound quality and this is true – partly because the traditional measures of THD+N or SINAD expressed as RMS figures are rather a broad measure. With this in mind, we have taken great care to make sure that not only is the RMS THD+N figure very good, but the CALLIA noise and distortion spectrum is beyond reproach and that CALLIA provides the most transparent listening experience.

Low Impedance Headphone Output

The headphone output is a low 4-ohm impedance, designed for the best possible performance. Settings switches on the rear panel of the unit provide suitable sensistivity settings for most headphone types, to avoid the risk of wide variations in level among different headphone models with impedances ranging from a few ohms to more than 250 ohms.

Easy Connectivity to Your Computer, Tablet or Transport

In CALLIA, we have created a unit that is compatible with the widest range of computer hardware by using a USB2 interface supporting UAC2 audio. CALLIA also supports S/P-DIF digital audio inputs.

The UAC2 (USB Audio Class 2) interface is supported natively in Mac OS, Linux and Android, and in Windows with WDM and ASIO drivers that we supply.

CALLIA supports S/P-DIF digital audio inputs on both optical TOSLink and “Phono” co-axial screened copper connections. Source selection, namely USB or S/P-DIF on optical or copper connections is automatic, though manual override is possible.

Audio Formats

CALLIA supports linear PCM in 2′s complement binary coding and, using the “DSD over PCM” (DOP) protocol, DSD at the original bit-rate (DSD64) and also at 2 x the original rate (DSD128). DSD Files encoded as “DOP” may be played with both ASIO and WDM drivers.

Your computer, tablet or transport will commonly decode formats such as mp3 to PCM prior to transmission to the sound card, so these formats will typically be supported on your device in the same manner as they would be with another sound card.

On the S/P-DIF inputs, DOP can also be used, but only at the original DSD bit rate (DSD64) as these connections do not have enough bandwidth for DSD128.

The ASIO native DSD format is not currently supported.

Balanced and Unbalanced Outputs

CALLIA offers balanced and unbalanced output formats at +14dBu and 2Vrms respectively. The balanced output is presented on professional XLR male pin connectors and the unbalanced (consumer) output is on industry-standard “Phono” co-axial connectors.

Unsurpassed Jitter Rejection

CALLIA uses the same “CleverClox” hybrid digital phase-locked loop (DPLL) circuitry as Prism Sound professional products. Prism Sound digital audio products re-generate ultra-stable clocks for best quality conversion.

In the 1990s following initial work by Prism Sound principals Ian Dennis and Graham Boswell, Prism Sound went on to pioneer investigation of the effects of timing jitter on analogue to digital (A/D) and digital to analogue (D/A) conversion. The company produced numerous technical papers many of which are now regarded as standard reading by todays audio engineering professionals. The company developed special test stimuli such as the “JTEST” signal for S/P-DIF and AES3 interconnections and also developed special measurement capabilities in its range of audio test & measurement equipment.


Over the years, Prism Sound’s reputation for audio quality has been matched by its reputation for after-sales support and technical advice. CALLIA has the benefit of that support and customers have access to one of the best technical teams in the business.

Callia at a Glance

• Plug, play and enjoy your music in all popular formats
• No-compromise, full Prism Sound audio quality
• Play in Windows**, OSX, Linux, iOS and Android ***
• Class compliant UAC2/USB for best compatibility
• ASIO drivers for Windows
• Windows WDM drivers (Vista and later)
• Play from disc transport/player device via S/P-DIF
• Optical and co-axial S/P-DIF inputs
• Playback at sampling rates from 44.1kHz to 384kHz
• DSD64/128 playback via DOP (S/P-DIF DSD64 only)
• Automated source selection, with manual override
• Balanced +14dBu XLR and 2V RCA phono outputs
• 4-ohm headphone output (adjustable sensitivity)
• Front-panel digital master volume control
• State-of-the-art clocking with hybrid 2-stage DPLL
• Fully-floating balanced architecture for low noise

* For mobile devices separate adaptors may be required.
** Requires supplied UAC2 drivers from Prism Sound.
*** Check your operating system version for UAC2 support.

Leave a Reply