What Class G Amplification Is – And Why the SA45 Matters
A Class G amplifier is a power amplifier that switches between multiple voltage rails depending on musical demand, aiming to combine the low‑distortion finesse of Class A/B with far higher power efficiency and lower heat output during real‑world listening. Arcam did not invent Class G, but it has refined the topology across several generations of products, culminating in the SA45 integrated amplifier that anchors this Class A/B vs Class G debate. The SA45 wraps Class G power with streaming, Dirac room correction and multiroom‑friendly connectivity, yet it still targets purist two‑channel listeners who care most about sound. According to Darko.Audio, Arcam has been Class G’s “most persistent champion” since introducing it in 2009’s AVR600, giving the company an unusual depth of experience with this less common topology. The SA45 is therefore a useful lens for assessing whether Class G deserves a place among high‑end audio amplifiers.
Inside the Arcam SA45: Design Choices and Practicalities
The Arcam SA45 review reveals a design philosophy that keeps the digital signal‑processing footprint lean while focusing on core sonic performance. Dirac Live room correction is onboard, but users can disable internal DSP for a purer analogue path by turning Dirac off and setting the number of subwoofers to zero, which prevents analogue inputs from being routed through the ADC. Thermally, the SA45 runs only a little warm to the touch, comparable to a Hegel H190 or Lyngdorf TDAI‑1120, countering assumptions that more complex rail‑switching necessarily means extra heat. Arcam’s Radia app reflects the same minimalism: it can play local files from USB‑A but cannot switch inputs, leaving that task to the front panel or remote. Text readability on the front display has been criticised from typical listening distances, highlighting how Arcam has prioritised acoustic and electrical performance over interface flair in this high-end audio amplifier.
Class A/B vs Class G vs Direct Digital: Listening Comparisons
In integrated amplifier comparison tests, the Arcam SA45 went head‑to‑head with the Hegel H190 (a traditional Class A/B design) and the Lyngdorf TDAI‑1120, which uses Lyngdorf’s direct digital approach alongside extensive DSP. Each amplifier brought distinct sonic and operational traits. The Hegel H190 stands as a reference for clean, muscular Class A/B power that many listeners know well. The Lyngdorf’s direct digital topology, paired with its own room‑correction system, leans into precision and configurability. Against these, the SA45’s Class G amplifier aims for a middle path: the ease and tonal naturalness associated with strong analogue designs, combined with more efficient power delivery and controlled warmth. In listening rooms from compact offices to larger acoustically treated lounges, these differences emerge as shades of dynamic punch, low‑level detail and perceived effortlessness at higher volumes, underlining that topology shapes character as much as specs.
Does Class G Deliver Real‑World Efficiency Gains?
On paper, Class G promises superior efficiency by dropping to lower voltage rails when music plays quietly, then calling on higher rails only for peaks. In daily use, the SA45 behaves like a well‑sorted Class A/B unit that does not run excessively hot, even when pushed. Interestingly, Darko.Audio notes that a Class D design such as the Marantz Model 10 can run hotter than the SA45, the Hegel H190 and the Lyngdorf TDAI‑1120, which undermines the idea that topology alone dictates operating temperature or efficiency. Instead, implementation matters. With the SA45, Arcam’s execution brings dynamic reserves without turning the chassis into a space heater, which will appeal to listeners with small rooms or furniture‑packed racks. The SA45 therefore supports the argument that Class G can bridge the gap between high‑power performance and sensible power consumption for demanding high-end audio amplifier users.
Where the SA45 Fits in the High‑End Integrated Landscape
Beyond the SA45 itself, Arcam’s broader Class G line clarifies how the technology can scale. For system builders who want Class G power without built‑in streaming, the SA25+ integrated offers a more stripped‑back option, while the A50 Signature pairs dual‑mono Class G amplification with a phono stage, DAC and HDMI eARC for flexible system building. In one suggested system, Darko.Audio would pair an Eversolo T8 streamer with the A50 Signature instead of choosing the SA45, trading Dirac Live for Eversolo’s richer streaming interface and screen integration. This highlights a key lesson from the Arcam SA45 review: Class G itself is not the only factor; the surrounding feature set, room‑correction priorities and user‑interface expectations all decide whether an integrated amplifier will suit a listener. What the SA45 proves is that Class G belongs in serious conversations about premium integrated amplifier design.
