Berkeley Audio Design Alpha USB Reference Series USB Digital Audio Interface

The Berkeley Audio Design Alpha USB Reference Series is a reference-grade USB-to-AES/EBU and USB-to-S/PDIF digital audio interface, engineered to isolate a music server or computer from the DAC while completely reclocking the outgoing digital signal. It combines asynchronous USB 2.0 High Speed Audio, proprietary ultra-low phase-noise clock technology derived from the Alpha DAC Reference Series 3P, extreme electrical isolation, a dedicated linear power supply and selectable 110Ω AES/EBU or 75Ω BNC S/PDIF output. Berkeley Audio Design

Rather than simply converting one digital connector to another, the Alpha USB Reference Series is designed to address USB-source noise, clock timing and electrical contamination before the signal reaches the DAC. It supports PCM up to 24-bit/192kHz and is specifically optimized for modern Linux-based music servers, Apple Mac and Windows computers. Berkeley Audio Design

Ultra-Low Phase-Noise Reclocking

The Alpha USB Reference Series uses ultra-low phase-noise audio output master-clock technology developed for Berkeley's flagship Alpha DAC Reference Series 3P. Berkeley Audio Design

Incoming USB audio is not simply passed through to the digital output. Berkeley reclocks the signal before transmission through AES/EBU or S/PDIF, creating a new precision-timed digital output for the connected DAC.

This architecture makes the Alpha USB Reference Series particularly relevant to DACs whose performance depends heavily on the quality and timing accuracy of their incoming AES/EBU or S/PDIF signal.

Complete USB-to-DAC Electrical Isolation

Berkeley places unusual emphasis on isolating the USB source from the DAC.

The USB receiver and processing circuitry are powered by the connected USB source, while the output master clocks and AES/EBU/S/PDIF line drivers operate from a separate isolated linear power supply. Berkeley Audio Design

Berkeley specifies three forms of isolation between the USB input and digital output:

• Galvanic / DC isolation
• Capacitive isolation
• Inductive isolation

There is no DC connection between the USB input and AES/EBU or S/PDIF output circuitry. Berkeley Audio Design

This prevents the Alpha USB Reference Series from becoming merely a physical bridge carrying server-generated electrical noise directly into the DAC.

Proprietary High-Speed, Low-Latency USB Software

Hardware isolation is only part of the design.

Berkeley developed proprietary USB 2.0 High Speed Audio input software optimized for modern high-speed, low-latency USB Audio drivers. The manufacturer identifies this software as one of the three fundamental technologies behind the Reference Series interface, alongside electrical isolation and ultra-low phase-noise output clocking. Berkeley Audio Design

This distinguishes the Alpha USB Reference Series from a generic USB-to-S/PDIF converter built around an off-the-shelf USB receiver implementation.

Asynchronous USB Audio 2.0 Input

The rear panel provides a USB Type-B asynchronous USB Audio 2.0 input.

The interface supports:

Sampling Rates: 44.1kHz through 192kHz
Word Length: up to 24-bit
Connection: USB Type-B
Protocol: USB Audio 2.0 High Speed / asynchronous Berkeley Audio Design

The Alpha USB Reference Series is designed for modern Linux-based music servers, Apple Mac and Windows PCs. Berkeley Audio Design

Selectable AES/EBU or 75Ω BNC S/PDIF Output

A front-panel Output Select switch determines which digital interface is active.

The available outputs are:

AES/EBU: 110Ω balanced XLR
S/PDIF: 75Ω coaxial BNC Berkeley Audio Design

This is especially useful in a reference system because the preferred connection can be selected according to the DAC rather than being dictated by the source.

A green front-panel status LED confirms USB Lock, while amber indicates Standby. Berkeley Audio Design

Why Berkeley Keeps USB Outside the DAC

Berkeley's current Alpha DACs do not incorporate conventional USB inputs. Instead, the company separates USB reception and processing into the Alpha USB platform.

That architecture allows the electrically noisy USB environment to be handled in a dedicated enclosure before the signal reaches the DAC. The Alpha USB Reference Series then supplies a newly reclocked AES/EBU or S/PDIF signal to the converter.

This makes the product particularly important when building a system around the Alpha DAC Reference Series 3P or Alpha DAC Series 3P, both of which provide AES/EBU, BNC S/PDIF and Toslink inputs rather than USB. Berkeley Audio Design

Increased Mass & Vibration Isolation

The Reference Series advances beyond Berkeley's Alpha USB Series 2 with increased enclosure mass and improved vibration isolation, in addition to the newer ultra-low phase-noise reclocking technology. Berkeley Audio Design

The Reference model measures 5.38 inches deep and weighs 2.8 pounds, compared with 5 inches and 2.5 pounds for the Alpha USB Series 2. Berkeley Audio Design

The goal is greater mechanical stability for the precision clock and digital-output circuitry rather than simply making the enclosure larger.

Dedicated Isolated Linear Power Supply

The Alpha USB Reference Series connects directly to AC mains and incorporates a dedicated isolated linear power supply for its output clocking and line-driver circuitry. Berkeley Audio Design

It accepts 100V, 120V or 240V AC at 50/60Hz through a standard IEC inlet and consumes only 3 watts.

Berkeley specifically designs the unit for continuous operation. Berkeley Audio Design

Alpha USB Reference Series Technical Specifications

These are Berkeley Audio Design's current published specifications for the Alpha USB Reference Series. Berkeley Audio Design

Alpha USB Reference Series vs. Alpha USB Series 2

The Alpha USB Series 2 already provides asynchronous USB input, galvanic/capacitive/inductive isolation, a separate linear supply for the output stage and selectable AES/EBU or 75Ω BNC output. Berkeley Audio Design

The Alpha USB Reference Series takes that architecture further with the ultra-low phase-noise reclocking technology used in the Alpha DAC Reference Series 3P, plus increased enclosure mass and vibration isolation. Berkeley positions the Reference model as its highest-performance implementation of the USB interface. Berkeley Audio Design

The headline format capability remains 24-bit/192kHz. The Reference model's advancement is therefore about lower time-domain noise, improved reclocking and isolation, not increasing the maximum advertised sampling rate.

Ideal Partner for the Alpha DAC Reference Series 3P

The Alpha USB Reference Series is particularly significant when paired with the Alpha DAC Reference Series 3P.

A USB-based reference system can be configured as:

Music Server → USB → Alpha USB Reference Series → AES/EBU or 75Ω BNC → Alpha DAC Reference Series 3P

The USB interface handles the electrically noisy server connection, isolates the source, reclocks the digital audio and then presents the Berkeley DAC with a precision AES/EBU or S/PDIF signal. Berkeley explicitly promotes the Alpha USB Reference Series and Reference Series 3P as a complementary digital front end. Berkeley Audio Design

That distinction is important for buyers comparing Berkeley with DACs offering built-in USB: Berkeley intentionally makes the USB interface a separate reference component rather than placing the USB receiver inside its flagship DAC.

Berkeley Alpha USB Reference Series at The Grid HiFi

The Berkeley Audio Design Alpha USB Reference Series is designed for digital systems where USB isolation and signal timing are treated as seriously as the DAC itself. It is particularly compelling for pairing a high-performance USB music server with the Berkeley Alpha DAC Reference Series 3P or Alpha DAC Series 3P.

The Grid HiFi can configure the complete Berkeley digital front end around the appropriate music server, USB connection, 110Ω AES/EBU or 75Ω BNC interface, DAC, amplification and loudspeakers.

Considering the Berkeley Alpha USB Reference Series? Call The Grid HiFi at (713) 218-8120 to build the complete reference digital front end around it.