If you are a vacuum tube enthusiast chasing uncompromising high-fidelity sound, the Fosi GR70 is a rare budget revelation that legitimately rivals flagship audio gear. In fact, after more than 30 years of owning audio equipment, this headphone amplifier stands out as my absolute favorite. It is the single audio product that inspired me to scour every corner of the globe for the finest vintage NOS vacuum tubes, and I can tell you without reservation that the journey was well worth it. By utilizing a pure pentode, single-ended design and a circuit architecture completely free of output transformers or hybrid solid-state elements, the background remains eerily silent. Without a trace of hum or hiss, this headphone amplifier projects an incredibly holographic 3D soundstage. Once paired with a high-quality linear power supply and top-tier NOS tubes, the GR70 steps far beyond being just "good for the money." It becomes an incredibly transparent reference component with a rich analog soul, and it is the exact amplifier I trust as my primary reference tool when evaluating and testing the custom linear power supplies I co-design for desktop audio platforms.

The sound it produces, both to headphones or for the V3 and Dali Oberon 1 is absolutely fantastic.

For the price it's a good amp.

I purchased the GR70 to have a tube amp that looked great on my side table. The low cost and beautiful dual channel tubes fit the bill so I bought it.

When paired with my Focal Celestee headphones which are quite sensitive, there is a little bit of noise from the tubes on high gain, though that's part of the tube charm! Important note - This is only noticeable when there's no audio playing though so doesn't detract from most music listening, though does come through on tracks which utilise silence throughout.

When paired with less sensitive headphones like my Sennheiser HD6XX or Hifiman HE-X4, I can output as much power as I like and can't hear any noise from the tubes.

Overall, if you're after a tube amp that doesn't break the bank, the GR70 is an easy recommendation and I'd definitely purchase again.

I’ve been writing off tubes for a while now but decided to pull the trigger on the GR70 after enjoying several other Fosi audio products, and I’m sure glad I did… it satisfies my quest for tube sound and I have not heard any of the issues that plagued my previous tube experiences. The tone controls really do improve any headphone I have plugged in so far. 10/10

I got my Hifiman Sundaras a few days before my GR70 arrived, and only my old NAD T752 HT amp had enough juice to drive them. And they blew my mind. And today, the GR70 dropped, and my mind has been blown ten times harder.

The Sundara + GR70 = an absolutely massive soundstage, and the bass reaches so low that it uses your jaw and skull to generate the same feeling in your feet that a subwoofer under your desk does. I had to constantly reach out to my QUAD center speaker and Carnival 7 subwoofer, to make sure they were not running at the same time as the Sundaras!

I have never heard anything like this in my 60 years, and I auditioned Stax electrostatic "ear speakers" that cost many thousands of dollars in the 90s. And they weighed a LOT.

It's because the GR70 tube amp provides "huge" instantaneous current, allowing the planar drivers to move with perfect speed and authority. The Sundaras’ planar diaphragms are extremely low-mass and responsive, so they reproduce true sub-bass - right down to 6 Hz.

My body senses both the tiny air pressure changes in the ear canal, and vibrations are conducted through my skull, spine, and chair. This tricks my vestibular system into thinking the bass is massive, even though there’s no real subwoofer!

In just the first few hours of listening, I have heard lyrics that have eluded me for a few decades in one case!

And the great thing about my ZD3/ZA3/GR70 system is that the GR70 kills two birds with one stone! It gets its input from the ZD3, and the GR70 output goes to the RCA inputs on the ZA3, while the ZD3 uses XLRs. This means I can switch back and forth between transistor pre-amp and tube pre-amp, but I haven't had a chance to try that yet, because I am finding it *very* hard to take the Sundaras off my head, driven by the incredible GR70.

I also can't wait to integrate my new X5 phono pre-amp and my fully restored NAD 5120 turntable into the ZA3 system, and add another ZA3 for mono blocks.

That's because recently the music has become alive for me - and in a way it never has before, and I am so excited to listen to my entire collection of 6,000+ songs and 1,000+ vinyl records. It all sounds so mind-bending thanks to Fosi, and their insane price-to-performance ratio, and instantaneous WAF - Wife Acceptance Factor.

And in fact, my wonderful wife absolutely loves her BT30D, with Gale Mini Monitors, and a passive Pioneer subwoofer. It's changed her enjoyment of music and anime dramatically.

WHAT A TIME TO BE ALIVE!

The product arrived in Ukraine within a month, it matches the description and can be recommended for purchase.

Nice and warm sound, not powered, but very warm and clear.

Hello everyone, today I would like to share my new audiophile experience. After reading in various forums that it is definitely worth trying out tube amplification, I decided to purchase another product from FOSI Audio. After careful research, I chose the GR70 from FOSI.

No sooner said than done – I ordered it, and it arrived quickly as usual. Packaged in the typical foil, I unpacked it and was once again amazed by the striking, attractive FOSI box.

When you open the box, you are greeted by another piece of high-quality, textured packaging.

First, I went to the tubes – once again, I was holding a high-quality product in my hands. The two different tubes were literally begging to be tried out, and I was excited to hear their sound characteristics.

As usual, the instruction manual is carefully explained and can be directly applied to your own system configuration.

The design impresses with its exceptional aesthetics and high-quality materials. Particularly striking are the orange power switch and the ventilation holes backed with orange mesh. Everything is made of high-quality aluminum; the glass tubes have protective borosilicate glass. The connections are clearly arranged and sorted.

Curious as I am, I also ventured a look inside the GR70. Here's a clear warning: openings in the device should only be made by experienced technicians, as a certain amount of dexterity and expertise are required.

The GR70 is not primarily intended for internal upgrades; however, tubes can be replaced with higher-quality models. Inside the housing, connoisseurs will find the high-quality chipsets and components they have come to expect from FOSI.

The direct practical relevance was important to me: I first connected the device to my existing system, consisting of the FOSI BT20 Pro, a FOSI DAC Q6, and Yamaha speakers. My first impression of the sound was that it was well-rounded, with electric guitars sounding nuanced and naturally powerful, and vocals coming to the fore. It was clear that the GR70 offers a compelling listening experience.

For comparison, I also tested the GR70 on my Pioneer system with JBL speakers – also a pleasure. I then tested the GR70 as a headphone amplifier. Borrowed from a friend, I first used a simple gaming headset as a reference, then a Beyer Dynamic DT 990 Pro with an open design. The result was impressive: the GR70 delivered balanced performance across all genres tested; highs and lows could be finely tuned thanks to flexible adjustment options. The headphones were so comfortable to wear that I hardly wanted to stop listening.

The idea of a new headphone option is gaining traction, and here too, the potential purchase of another FOSI product is being considered. One further note: the glass tubes look extremely impressive when lit up and add an attractive visual element to their surroundings.

In summary, the GR70 is another very successful device from FOSI and a worthwhile purchase for anyone looking for a compact, affordable tube amplifier. It can be seamlessly integrated into both simple and high-quality systems and remains one of my favorites.

Sound incredible good in my ears
Tears in my eyes
Bobbles on my skin
i could not believe that

A well-assembled device, the sound is excellent!!! Not very suitable for heavy plans.

Everything is very good! The packaging is secure, the seller is pleasant to communicate with, and the delivery is fast. I recommend this amplifier and the seller! It really worths its money! Sounds amazing!!! Thank you very much!!!

Just look at how beautiful it is.

This is one of the best addition that you can get for your entire chain at this price.

Even using it as a simple amplifier, you cannot go wrong choosing it if you want tubes.

The sound is sweet and clear, there's no chocolate nor muddy sensation in it.

It refines the treble region, adding a little slowness while it feels with more extension. This can be translated into a response of organic smoothness.

Match it with the i5 and you'll get an enjoyable dynamic sound experience.

Is it too much bass? EQ -2 or -4 db and it will be as clear as your solid state reference. But believe me that you are enjoying it without eq.

The construction is really solid and well done. I'd like more resistance in the main volume knob, because is sensitive, so be careful when you use IEMs.

Fosi Audio GR70 Tube Headphone Amp

Solid & solid. Bass can explain whether it is muddy or delicious. When the trebel ejas has a mid, it goes up a little to make the sound soft. Best crazy pair with Fosi k7. I use Sony Mdr Mv1, Sennheiser Hd800s, Focal Clear Mg Pro headphones.

I’ve been enjoying this product very much—using it as a preamp—and yes, it delivers a sound that softens some of the harshness of digital sources, adding that famous warmth.

It is beautiful and sounds beautiful whether used as an amplifier or pre-amplifier.

Very cool. 😎 It works and sounds great. I’m using it as a preamp as well as a hp amp. 4 tubes! Super fun. 🤩