Fosi Audio GR70 Tube Headphone Amplifier Preamplifier – Pure Void Lamp Power
Fosi Audio GR70 is a 229 USD Pure Tube Amplifier for headphones, with adjustable impedance, bass and treble, and it can also work as a preamplifier. Today we will review the GR 70 and see how it fits in the busy market of audiophile products.
Introduction
Fosi Audio is slowly migrating from once an entry-level and budget-friendly company to now being a standard hi-end and interesting audiophile company, with multiple products under their belt, some of which having been extreme commercial success like their Fosi Audio i5 headphones, a 549 USD pair of headphones that is slowly becoming even more popular than alternatives from Sennheiser.
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Product Link
Amazon – https://amzn.to/4shXiqg
Aliexpress – https://s.click.aliexpress.com/e/_c3wWyRgP
Build Quality – Design
Body Material – CNC-machined aluminum alloy — described as durable and refined, Compact form factor with dual-side ventilation holes for heat dissipation, Physical Controls & Design Elements
GR70 has three controls, including
- Large volume knob
- Bass & treble control knobs
- High/Low impedance mode switch
Vacuum Tube Configuration is novel and rare for this price point, and it is a Quad-tube design using
- 2× 5654W tubes for voltage amplification
- 2× 6Ж4/6Ж8 tubes for power amplification
We also have two Headphone Outputs
- 6.35 mm (1/4″) jack
- 3.5 mm jack
And all the other connections are RCA Connections with the entire device being single ended. We have one Stereo RCA input and one Stereo RCA output. You can select the impedance between low and high, but the impedance level changes a few of the characteristics too. Inside the package, you have Included Two vacuum tube protection covers, one Power Supply (DC 12 V/3 A) and user manual included.
Subjective Usage
At its core, GR70 is really mispriced, it could have easily been over 500 USD if produced by anyone else, and it is impressive. From what Fosi used to deliver, fairly industrial and simplistic products, we now have what I consider to be the ultimate beauty, incredibly smooth and clean. Not only does GR70 solve the old age dilemma of burning your fingers on tubes by using transparent protectors around the tubes, but the large volume wheel at the top feels smooth and has a super satisfying turn to it, and the jacks at the front are high quality.
You can rely on the high-quality RCA inputs and outputs at the back as well, and if you’re courageous you can touch the large pentodes at the back and feel them heating up and burning with desire to produce music. This is an interesting experience for me as the 6W8 and 6W4 pentodes produce a unique tuning that is what I would’ve expected if you told me how it works.
I like how it sounds in low gain, and usually do not need to give it high gain, and while Fosi made it accept low impedance headphones it mainly sounds a bit better with high impedance headphones, as they can filter the tube noise. Everything is fully single ended but with adapters from ddHIFI I’ve been able to use GR70 with balanced cables too. It runs hot, as you’d expect from tubes, and the 2-stage amplification handles voltage and power separately.
Sound Quality
Pairings – For testing it as a headphone amplifier, have paired the Fosi Audio GR70with a selection of headphones and IEMS, including Lily Audio Genesis One, Raptgo LEAF D01, Palma DHS-1, KBEar Cepheus, Crosszone CZ-10 Enhanced, Erzetich Thalia, TinHIFI T7, NFAudio NE4, Sivga Peng, Crosszone CZ-8a Enhanced, Tangzu TianPeng, Soundz Flame, YanYin Canon PRO, Dunu Vulkan 2, Letshuoer Mystic 8, Moritz Aura, HarmonicDyne Romantic, HIFIAN HE600, HIFIMAN Audivina LE, HIFIMAN Ananda Unveiled, Westne Mach 80, BQEYZ Winter II, Fosi Audio IM4, Aune AC55, Oriveti Bleqk PureCaster and Noble Knight.
You can absolutely hear the tube noise, hum and EFI / RFI with sensitive IEMs, but this is not audible with headphones, and for the most part I can enjoy GR 70 with Moritz Audio Enzo too, without minding the noise. Max driving power is not extremely high, but it is enough for the likes of HIFIMAN Audivina LE, HEDD D1, and it pairs really well with some IEMS like Noble Knight.
Overall Signature – Fosi GR 70 is a warm sounding headphone amplifier, it has a strong backbone, a smoother, more lush midrange and a beautiful vocal range. It has a slower, deeper bass, crisp treble with a good extension and generally draws all of the strengths of a tube sound, combines them with the elusive magic of a pentode and delivers a signature that’s enjoyable, beautifying rock, metal, edm and all music styles. It is quite versatile and universal, magical at its core, delivering an organic and fun, jumpy, bumpy presentation. Since we have both a triode and a pentode, it is a good moment to mention that the triode will produce a more splashy and more textured midrange, while the pantone will influence the bass and treble, giving more presence to the two extremes.
Bass – With a powerful, deep and somewhat slow deep end, GR70 renders a heavy bass that gives music body, weight and impact. It is impressive for all styles, but excels for rock, edm and pop music. This slower bass does not combine as well with classical, as it gives instruments a bit too much decay and presence in the low end. Bass gain is effective, it adds both sub bass and some mid bass from 50 Hz to 80 Hz, while treble enhances the upper midrange and treble, starting with about 6 kHz and up to 12 kHz.
Midrange – Vocals and mids in general clearly favor real instruments, as GR70 has a bit of that tube magic, gives instruments a rich texture, an organic and pleasing tone, and a smoother, more fluid presentation. This emphasizes guitars and basically every acoustic instrument, it gives a bit more texture, vibration, which adds something that naturally isn’t there in synths, but works really well for instruments in general, especially electric guitars which have a bit of added distortion.
Treble – With a sharp, strong and brilliant top end, GR70 does not miss the treble, but rather delivers it completely, in abundance, but with a wet texture that takes away harshness and replaces it with a bit of sibilance and splashiness. This works well for rock, metal, edm and pop music. Treble extends as high as your headphones or IEMS will, up to 20 kHz, with the splashy effect starting early on, from the upper midrange.
Dynamics And Textures – GR70 has a natural dynamic range, not overly dynamic, nor compressed, but it does something special to textures, it defines textures as far more expressive, more vivid than they’re supposed to be. This means that there’s more grain too, more vibration to music, more texture, but this is a normal effect usually audible with all tube amps to some degree and the main reason you’re buying them.
Loudness Saturation Gradient – At the loud end, GR70 does not have a much heavier distortion, it stays controlled and clean even if you pump the volume considerably. Quietly, you hear more of the noise floor, especially if the DAC sends computer noise to GR70, like a strong GPU, as it is single ended. It is best if you are inclined to enjoy music medium and loud.
Soundstage – Wide a natural-wide soundstage, GR70 sounds vivid and realistic, it drives color and punch into music, gives instruments space to breathe without surgically separating them. It is a great amplifier if you want a mostly natural presentation.
Value – Conclusion
GR70 has a low price and high performance, it is an excellent choice if you’re looking to color the sound of your headphones. It has a uniquely good build quality, and as I mentioned in the review, it could have easily cost over 500 USD and still be a strong value in today’s market.
Fosi delivered something really interesting, and they are moving away from being an entry-level company all the way to producing reference, interesting products with a high quality, still affordable prices, but actual respectable hifi quality.
PROs
- Excellent build quality and design
- Most affordable tube amp that implements both triodes and pentodes
- High driving power for the price range
- Top resolution for the price range
- Splashy and harshness-free treble
- Slow and punchy bass
- Vivid and organic midrange with a good resolution
- Excellent overall choice for the money
Cons
- Runs really hot, as expected of having 4 tubes in total, 2 triodes and 2 pentodes
- Audible noise with sensitive IEMS, EMI, RFI, videocard noise transmitted from my computer, due to the SE design
- Replacing both triodes and pentodes might end up costing a lot down the line
Product Link
Amazon – https://amzn.to/4shXiqg
Aliexpress – https://s.click.aliexpress.com/e/_c3wWyRgP
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Full Playlist used for this review
We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature. I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!
https://www.youtube.com/playlist?list=PL_cjBXGmwSHSdGcwuc_bKbBDGHL4QvYBu
https://open.spotify.com/playlist/5J3oloz8Riy9LxEGenOjQ0?si=979ba4f082414be7
https://tidal.com/browse/playlist/330fd544-8e5b-4839-bd35-676b2edbb3d5
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