This article explores Arcam’s latest additions to their Radia Series: the ST25 music streamer and the SA35 and SA45 streaming integrated amplifiers. These new models blend advanced streaming technology with Arcam’s decades-long dedication to high-performance audio. Whether you're pulling tracks from your personal music library or streaming from your favorite service, these components are designed to deliver exceptional sound quality. In this overview, we’ll break down the features and performance of each model to help you choose the right fit for your system.

Company History

A&R Cambridge Ltd., better known as Arcam, was founded in 1976 by science and engineering students from the University of Cambridge. From the beginning, their focus was clear: design audio components that deliver exceptional sound quality, straightforward usability, and long-term reliability.

Their very first product—the A60 Integrated Amplifier—started as a passion project for friends and family. It quickly earned industry recognition and set the tone for everything Arcam would go on to build. Many A60s are still in use today, a testament to the robust, high-quality components Arcam used, including premium power supply transformers, capacitors, and output stages.

Following the success of the A60, Arcam continued to innovate with standout products like the P77 phono cartridge in 1977 and the Arcam Two stand-mount speaker in 1985. Then in 1988, they introduced the “Delta Black Box” DAC—widely regarded as the first outboard digital-to-analog converter. At a time when most music lovers hadn’t even considered the need for an external DAC, Arcam helped spark a trend that’s now a hallmark of reference-level audio systems.

Today, Arcam is a leading name in British high-end audio, offering both 2-channel and home theater solutions that pair modern technology with timeless design and unmistakably British sound. With their sound-first engineering approach, every Arcam product is crafted to deliver an exceptional listening experience.

We're so impressed with Arcam's legacy and innovation that we’ve put together a full Radia Series Overview, diving deeper into the technology and design philosophy behind their latest lineup.

Features and Technology

ST25 Standalone Music Streamer

Internally, the ST25 features a newly designed toroidal transformer-based linear power supply. This delivers clean, stable power for optimal performance—and it’s a big step up from the switch-mode power supplies found in many streamers, which can introduce noise and reduce long-term reliability.

The transformer is positioned well away from sensitive audio paths, and the entire layout is housed in a spacious enclosure designed to minimize interference. Arcam also upgraded the chassis materials, using anodized aluminum on the front, top, and rear panels. Not only does this give the ST25 a premium, durable finish—it also improves sound quality over previous models by further reducing vibration and resonance.

At the heart of the ST25 is the ESS ES9027Pro DAC, configured in an 8-channel summing, balanced configuration. All eight DAC channels are used in parallel and summed together. This approach significantly increases dynamic range while keeping the noise floor extremely low. That’s because the audio signal sums together coherently, but noise—being random—doesn’t add up the same way. And since the ST25 operates in a fully balanced configuration, it further reduces the impact of any remaining noise.

Physically, it measures 17 inches wide by 13.5 inches deep and 4 inches tall, and weighs in at 11 pounds. It’s solidly built, yet compact enough to fit cleanly into just about any system.

The ST25 can handle a wide range of audio formats—including FLAC, WAV, AAC, ALAC, AIFF, DSD up to DSD256, MP3, MP4, OGG, and WMA—at resolutions up to 32-bit, 384 kilohertz. Simply put, it’s built to manage nearly any streaming format available today and is well-equipped for whatever comes next. And with Roon Ready certification expected soon, it’s shaping up to be one of the most versatile and high-performance streamers in its class.

The back panel of the ST25 is clean, clearly labeled, and thoughtfully laid out, making it easy to find the connections you need. There’s a standard IEC power input for the included power cord—or your preferred upgraded option—and a master power switch. For audio output, you’ll find Toslink and coaxial digital connections, as well as analog RCA outputs that utilize the ST25’s high-quality internal DAC. This means it can integrate seamlessly into older analog systems or provide a digital signal to a newer component with its own DAC.

Additional connectivity includes a USB port for music storage devices and an Ethernet port if you prefer a wired connection over the built-in dual-band Wi-Fi. There's also a 12V trigger output to power on other compatible components when the ST25 is activated.

One particularly thoughtful touch is the dedicated control jack that links directly to the Radia A25 Integrated Amplifier. When connected, the ST25 and A25 operate as a single unit—fully controllable via the Arcam app or remote—as if they were built into the same chassis. For Radia A25 owners, this makes integration incredibly clean and user-friendly. Overall, Arcam has done a fantastic job making the ST25 flexible enough to work in virtually any system, while still offering seamless integration with its Radia sibling.

ST5 vs ST25 Streamer

If you're considering a high-performance music streamer from Arcam’s Radia Series, both the ST5 and ST25 are great options, but they cater to slightly different needs.

The ST5 is the more budget-friendly model, designed with a compact, minimalist aesthetic and a simple one-line text display. It uses an ESS ES9018 DAC and supports high-resolution playback up to 24-bit/192kHz. It’s a great fit for systems using the Arcam A5 or A15 amplifiers, or for anyone looking for a straightforward, great-sounding streamer without added features that might go unused.

The ST25 takes things a step further. It features a more robust chassis, a linear toroidal power supply for cleaner power delivery, and ESS’s more advanced Hyperstream IV DAC. It supports a wider range of audio formats up to 32-bit/384kHz and includes a 6.5" high-resolution color display that shows album art and track info clearly from your listening seat. It’s designed for those who want not just excellent performance, but a more immersive and refined user experience as well.

In the end, the ST5 is ideal if you’re looking for simplicity and value, while the ST25 is the better choice if sound quality, visual feedback, and future-proof specs are your top priorities. Both offer wide streaming support, including Spotify Connect, Tidal Connect, Apple AirPlay 2, and Chromecast. The ST5 is Roon Ready and the ST25 is still awaiting certification as of April 2025.

SA35 and SA45 Streaming Amplifiers

For those looking for an all-in-one solution, the Arcam SA35 and SA45 streaming integrated amplifiers combine high-quality streaming with Arcam’s renowned Class G amplification in a single chassis. These are not stripped-down systems that sacrifice quality for convenience—they’re full-featured, high-end streamers and amplifiers that compete with separates in both performance and flexibility.

The design is unmistakably Arcam: minimalist, elegant, and solidly built with an all-metal chassis. Subtle yellow accents add a modern touch, helping illuminate the control knobs on the front panel. While some may view black components as plain, Arcam manages to make simple look sophisticated. Both models feature intuitive front-panel controls—input selection on the left and volume (with push-to-mute and long-press standby) on the right. The SA35 uses the same 6.5” high-resolution display as the ST25, while the SA45 steps up to a larger 8.8” screen for even easier readability from your listening position. The SA35 measures 17” x 13.5” x 4” and weighs 26 lbs, while the SA45 is slightly larger at 17” x 15.5” x 5.5” and weighs 37 lbs. Both are impressively solid for their class.

Connectivity is just as robust. Both models support Bluetooth 5.4 with aptX Adaptive and dual-band Wi-Fi, as well as Ethernet for wired networking. They use the same streaming platform as the ST25, supporting all the major formats and services, with a user-friendly interface and crisp display.

The rear panels of the SA35 and SA45 are cleanly laid out, clearly labeled, and packed with thoughtful connection options. Starting with the SA35, you get three analog RCA inputs along with dedicated MM and MC phono inputs. This makes it easy to connect virtually any turntable, whether you’re using a moving magnet or moving coil cartridge. Even better, the presence of two separate phono inputs opens up the possibility for running dual tonearms or multiple turntables—something that serious vinyl enthusiasts will appreciate. Just keep in mind that one of the inputs is limited to MM, but the flexibility here is still impressive for an integrated amplifier. They also include full-range preamp outputs, which means you can use either amp as a streaming preamp down the line if you ever decide to move to external amplification.

Finally, let’s talk about two of our favorite features found on both of these amps. First, they include dual subwoofer outputs—a big plus, since running two subs typically delivers more balanced and impactful bass across the entire listening area compared to a single sub setup.

Second, both models include Dirac Live Room Correction, which allows you to precisely calibrate your system to your room. Dirac analyzes your space’s acoustics and makes real-time adjustments to timing, frequency response, and phase alignment—helping you achieve a more accurate and immersive listening experience. It also handles crossover and bass management between your speakers and subs.

Right now, the subwoofer outputs are optimized together in common with your main speakers. But Arcam designed these amps to support independent subwoofer measurement and optimization. That feature is expected in a future firmware update, which will unlock even more precise tuning—especially for systems with asymmetrical sub placement.

We are huge fans of room correction, and the fact that these two units have this included without an additional purchase, like other products on the market, is just fantastic! Dirac is one of the best room correction software’s on the market today, so we highly recommend you take advantage of it with both of these. And even if you’ve never used it before, we have an in-depth tutorial that walks you through how to use it and our team of experts are here for you if you have any questions.

Next, the SA45 takes things a step further with additional balanced connections, including a balanced analog input, a balanced main output, and dual balanced subwoofer outputs. This level of flexibility makes the SA45 ideal for more complex systems that benefit from balanced connections—especially where longer cable runs are involved. Balanced cables help with noise rejection and can provide a cleaner signal path, which is especially valuable when running subwoofers across larger rooms or integrating the amp into a more advanced audio system. It's great to see Arcam include these options, and it speaks to their commitment to both performance and future system expansion.

Digital inputs are generous on both models, with two Toslink optical and two coaxial digital inputs for your digital sources. HDMI ARC/eARC is also included, allowing for easy integration with your television so you can enjoy dramatically better sound while watching movies or TV. Both units also provide USB inputs for music playback from external drives, Ethernet ports for hardwired network connections, and IR inputs for integration with control systems. Rounding out the rear panels are high-quality binding posts that accept a variety of speaker cable terminations, once again showing Arcam’s attention to detail and commitment to compatibility.

Arcam clearly put a lot of thought into the rear panel design of both the SA35 and SA45. Whether you’re building a compact vinyl-based setup, integrating with a TV, expanding into a full-range two-subwoofer system, or looking toward future outboard gear, these amplifiers are equipped to handle just about anything you throw at them.

Arcam has long stood by its Class G amplifier technology, and with good reason. It’s been a key part of their design philosophy for years, and the SA35 and SA45 represent the fifth generation of this proven approach. At the core of Class G is a toroidal transformer with dual voltage rails, which allows the amplifier to operate more efficiently while still delivering outstanding sound quality across the entire volume range.

At lower listening levels, Arcam’s Class G amplifier uses the lower voltage rail, operating in pure Class A mode—delivering that warm, detailed, and natural sound that audiophiles love. But when more power is needed, rather than switching abruptly between voltage rails—which can introduce unwanted noise or artifacts—Arcam takes a smarter approach.

They’ve developed a “lifter” circuit, using a group of FETs that dynamically raises the voltage across the output stage above that of the lower supply rail. This circuit tracks the audio signal in real time, adding about five volts of headroom to ensure the amplifier never runs out of power—even at maximum output.

The result is that you get the benefits of dynamic voltage operation—like efficiency and power on demand—without the switching artifacts that are common in typical Class G or Class H designs. It’s a cleaner, more elegant approach that allows Arcam to deliver smooth Class A performance when possible, and full-throttle Class A/B output when needed—without compromise.

One of the big advantages here is efficiency. Unlike conventional Class A/B amps, Class G avoids crossover distortion between the positive and negative transistors by operating in Class A during low-power playback, where most listening takes place. And compared to Class A, which runs full voltage all the time and generates a lot of heat, Class G wastes far less energy and runs cooler, even when driving demanding speakers. It’s also distinct from Class D amplification, which switches the audio signal at high frequencies using a completely different method. Arcam’s Class G, by contrast, doesn’t switch the audio signal at all—it only manipulates the power supply. This allows it to retain the analog character of traditional amplification while still delivering a more efficient, intelligent power delivery system.

In real-world terms, Arcam’s Class G design gives you detailed, smooth, and dynamic sound at low levels, plus all the impact and control you need when the music swells. It’s a thoughtful engineering solution that balances performance and efficiency—one of the reasons Arcam has continued to refine and stick with it over the years.

The SA35 is rated at 120 watts per channel into 8 ohms, while the SA45 steps things up to 180 watts per channel into 8 ohms. Both amplifiers are 4-ohm stable, which means they’re more than capable of powering a wide range of speakers—even those that are a bit more demanding. These are excellent power ratings for integrated amps in this class, and either model will have no trouble driving most speakers in typical listening environments.

In addition to their impressive power output, both the SA35 and SA45 share the same high-performance DAC platform found in the ST25 streamer. Built around ESS’s advanced Hyperstream IV architecture, this DAC delivers excellent clarity, resolution, and dynamic range—ensuring your digital music sounds its absolute best, no matter which model you choose.

Unlike the ST25, the DAC implementation in the SA35 and SA45 doesn’t sum all channels together. Instead, it’s configured in a balanced architecture with dedicated DAC channels allocated to the left and right outputs, as well as the two subwoofer outputs.

Choosing between the two comes down to your specific needs. If you have a larger room, speakers with lower sensitivity, or you simply want more headroom for dynamic peaks, the SA45 is the clear choice. It also gives you some additional connectivity options that might come in handy depending on your setup.

That said, the SA35 is no slouch. In fact, it will drive most tower speakers wonderfully well. For those who can’t quite stretch to the SA45, don’t write off the SA35—it delivers clean, authoritative power and has everything most systems will ever need.

Arcam Radia App Control

The ST25, SA35, and SA45 are compatible with Spotify Connect, Tidal Connect, and will be Roon Ready soon. They also support Apple AirPlay 2, and you don’t need the Arcam app to use it—aside from initially connecting the device to Wi-Fi. That said, the Arcam app does give you even more flexibility. It allows you to stream from Qobuz and Amazon Music, access UPnP streaming and USB drive playback, and even tune in to podcasts and internet radio stations—all from one place.

This is one of the ST25, SA35, and SA45’s biggest strengths—you’re not locked into a single streaming service. The Arcam Radia app lets you access music from your favorite platforms like Qobuz, Tidal, Amazon Music, and Spotify Connect, while also giving you the flexibility to stream via Chromecast or AirPlay from any other source. Whether your music is stored locally or in the cloud, you’ll have a wide range of options to get to your favorite tracks. This “streaming Swiss Army knife” approach is exactly what we love to see—it gives users more freedom and fewer limitations when building their system around the services they already use.

The app itself is cleanly designed and easy to navigate, keeping in line with Arcam’s overall philosophy of simplicity and usability. It won’t take long to feel at home using it, even if you’re new to high-end audio.

All three products also come with a thoughtfully designed remote that handles basic functions and menu navigation with ease. It shares the same yellow-accented styling as the rest of the Radia series, keeping the look consistent across your system. The layout is intuitive, with a prominent volume rocker and a simple navigation pad with a center select button. If you’ve used a modern streaming remote before, this will feel instantly familiar—another nice touch for making these products approachable without sacrificing quality.

Conclusion

There are a lot of streaming options out there. Some focus on features, others on sound—but when a product delivers both, that’s where the magic happens. The Arcam ST25 hits that sweet spot, offering broad streaming compatibility alongside top-tier audio performance thanks to its advanced DAC and premium internal components.

For those who want everything in one box, the SA35 and SA45 add Arcam’s legendary Class G amplification, full streaming support, and Dirac Live Room Correction to the mix, creating powerful, full-featured streaming integrated amplifiers that don’t compromise on quality.

Whether you're building a dedicated music system or looking for a streamlined all-in-one solution, you owe it to yourself to check out the ST25, SA35, and SA45. If you have any questions or want help deciding which model is the best fit for your system, our team at Audio Advice is here to help—just call, chat, or email us anytime. We’d love to help you find the perfect match.

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