Fosi Audio GR70 Tube Headphone Amp

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

I just got my GR70 and so far I am REALLY HAPPY with the product. My digital setup suddenly became mellow and buttery to my ears. I’m using it as a preamp to my Marantz M50, connected to a pair of first-gen Klipsch RP600M. Very happy with the results! I wonder if I can replace the stock 6AC7 tubes with a pair of PSVANE EL34C. Can anyone at Fosi help me with this question?

If you want the warmth of class a tubes this is the one to go for complete analog. It's like listening to recordings from the 1970s and 80s beautiful sounds smooth as silk warm. Lots of bloom exactly what you want for old school stuff.

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.