The Fosi Audio GR40 is a compact, affordable device that punches far above its weight. This review delves into the performance of this surprisingly robust little unit, which boasts a compelling combination of features rarely seen at its price point: a high-resolution ESS9028Q2M DAC, a warm-sounding tube preamp stage utilizing GE 5654 tubes, and a built-in headphone amplifier. Initial impressions focused on its build quality and surprisingly small footprint, making it ideal for various setups. We explore its versatility, including Bluetooth connectivity with support for multiple aptX codecs.The review then dives into a detailed analysis of the GR40's sound quality, comparing it directly to the more expensive FiiO K11 R2R. We examine its performance with both IEMs and full-sized headphones, noting any minor drawbacks and highlighting its strengths. Ultimately, this review aims to determine whether the Fosi Audio GR40 truly delivers insane value as its marketing suggests, and whether its impressive specifications translate into a superior listening experience.
Pros And Cons
- Inexpensive (cheap)
- Excellent sound quality with most audio sources (excluding IEMs)
- Includes DAC, tube preamp, and headphone amp
- Handles DSD 256 and PCM up to 384 kHz
- Bluetooth receiving capabilities with various codecs (including aptX HD, aptX Adaptive, and aptX LL)
- Natural, beautifully separated, and very clean sound
- Good resolution and enjoyable timbre
- Tubes balance beautifully with the DAC chip
- Significant hiss with IEMs
- Significant channel imbalance from volume control below the 9:00 mark
- Lacks LDAC codec
Read more: Fiio K11 R2R DAC/Amp Review: A Worthy Upgrade or Redundant Luxury?
Unboxing and First Impressions
The Fosi Audio GR40 arrived, a compact device promising much more than its affordable price tag suggests. Initial impressions were positive; the build quality felt surprisingly robust for a budget device. The inclusion of both tubes and a DAC was an exciting prospect.
The packaging was simple but effective, protecting the unit during transit. The device's small footprint immediately indicated that it would fit easily into most setups, even on a cluttered desk.
Technical Specifications and Features
The GR40 boasts an ESS9028Q2M DAC chip, capable of handling high-resolution audio files up to DSD256 and PCM 384kHz. This impressive spec sheet is further enhanced by its integrated tube preamp stage using GE 5654 tubes, promising a warm and detailed sound.
Bluetooth connectivity with support for aptX HD, aptX Adaptive, and aptX LL codecs ensures versatility. The inclusion of a headphone amp adds further convenience.
Sound Quality and Performance
The GR40's sound quality is remarkably good, especially considering its price. While some minor hiss was present with IEMs and slight channel imbalance at low volumes, these were insignificant with full-sized headphones.
The soundstage, though not exceptionally wide, offered good resolution and a pleasing overall tonality. The warm tube characteristics combined beautifully with the clarity of the DAC chip.
Comparison with the FiiO K11 R2R
A comparison with the FiiO K11 R2R, a more expensive device, revealed interesting results. While the K11 offered additional features such as line-out mode and non-oversampling, the GR40 outperformed it in terms of overall sound quality.

The GR40 presented a smoother, more natural sound compared to the K11's slightly grainier and drier presentation. The GR40’s superior tonality made it more enjoyable to listen to.
Conclusion and Verdict
The Fosi Audio GR40 is a surprising and impressive performer, excelling at its price point. The combination of the ESS9028Q2M DAC chip and the tube preamp stage results in a remarkably natural, detailed, and clean sound.
While the FiiO K11 R2R is a capable all-in-one device, the GR40 is the clear winner if your priority is pure DAC performance. Its versatility, thanks to Bluetooth and multiple output options, is another factor in its favor. Highly recommended!