Cyrus 40 ST Streaming Transport

There is a reasonable argument that a streaming transport is the most important component in a modern system. The amplifier amplifies what it receives; the speakers reproduce what the amplifier sends them. The streamer decides what that signal is in the first place. Get it wrong at source and nothing downstream can correct it. The Cyrus 40 ST is built on the premise that a dedicated streaming transport — one that does nothing else — will always outperform a streaming function built into an amplifier as a secondary feature.

BluOS Streaming Platform

The 40 ST is built around BluOS — a streaming platform developed and maintained independently of Cyrus, which means its development roadmap does not depend on Cyrus's internal software team. That matters for longevity: BluOS receives regular updates, supports a wide range of streaming services including Tidal, Qobuz, Spotify, and Amazon Music, and handles locally stored music via UPnP or USB. The controller app runs on iOS and Android and provides a consistent, well-designed interface for library management, playback, and playlist building.

Multi-room functionality is included natively. If other BluOS-enabled devices exist elsewhere in the house, the 40 ST integrates with them without additional configuration.

ESS Sabre ES9039Q2M DAC

The DAC is built around the ESS Sabre ES9039Q2M 32-bit chipset — the same architecture used across the 40 Series. The 40 ST also accepts external digital sources via coaxial and optical inputs, allowing it to serve as the DAC for a television, disc player, or any other digital device in the same room. Two line level analogue outputs feed downstream components, and both coaxial and optical digital outputs are provided for those who want to use the 40 ST as a transport feeding an external DAC.

Network Connectivity

The 40 ST connects via Gigabit Ethernet (GigE 1Gbps) or Wi-Fi 5 (802.11ac, 2.4/5GHz) via a built-in antenna. A wired connection remains the preferred option for critical listening — it eliminates the variability of wireless and ensures the lowest possible latency. The Wi-Fi implementation is robust enough for everyday use in most homes, but for a component at this level, a wired connection is worth planning for. A USB-A socket is also provided for direct music playback from a connected storage device.

40 PSU Upgrade

Like all 40 Series components, the 40 ST accepts the Cyrus 40 PSU external power supply. When connected, the 40 PSU takes over powering the analogue side of the DAC and the BluOS network module, providing a cleaner, more stable supply to both. The result — as Cyrus describe it from their own listening — is greater detail, better control, and more space around instruments and vocals. The improvement is specific and measurable; it is not an incremental refinement but a meaningful step in what the 40 ST is capable of.

Chassis and Display

The 40 ST is housed in the 40 Series hard-anodised aluminium chassis. The front panel is toughened glass with hidden-until-lit capacitive touch controls. The 5-inch full-colour TFT display provides clear visibility of the current source, streaming service, track information, and playback status. A full-function remote is included and integrates with the wider 40 Series range for unified system control.

Technical Specifications

Who Is It For?

The 40 ST is for the listener who wants a dedicated streaming source at the top of the Cyrus range — one that handles every major platform, accepts external digital sources, and outputs at a level that stands alongside the best disc-based players. It is the natural digital hub of a complete 40 Series system, pairing directly with the Cyrus 40 Amp and sitting alongside the Cyrus 40 CD for those who want both streaming and physical media covered at the same standard.

Those who want to go further should consider adding the Cyrus 40 PSU — it is the most significant single upgrade available to the 40 ST, and it is worth planning for at the time of purchase rather than as an afterthought.

Buying from Martins Hi-Fi

Martins Hi-Fi has been in Norwich since 1968. Elizabeth Gould runs the business today, and we stock only brands we have heard properly and stand behind.

The 40 ST is available to hear in our Norwich showroom, partnered with the 40 Amp and appropriate loudspeakers — including a direct comparison with disc-based sources if that is a question worth answering before you commit.

When you get in touch, you'll be speaking with Dave, Chris and Tim — experienced specialists who can advise on this product and your whole system.

Contact us at info@martinshifi.co.uk, call 01603 627010, or WhatsApp on 07554 687137. You can read more about how we work on our Why Martins Hi-Fi page. We are at 85–91 Ber Street, Norwich, NR1 3EY.