Fosi Audio GR40 Tube Preamplifier with DAC, Stereo Headphone Amplifier 3.5mm Home Audio for Active Speakers/Headphones, Digital to Analog Audio Converter Preamp with Bluetooth and USB/Opt/Coax

Very good for desktop DAC used with PC for digital music, albite lacks a bit of power for the headphones

Son muy útililes los controles de graves y agudos, con control de medios sería perfecto

This is my first venture into HiRes sound and this headphone amp / DAC is fantastic! I am sitting next to the singers! Highly recommended! I have hearing problem and hearing aids are not cutting it for me as there is always sound missing and music I loved just didn’t sound like I remembered it. Now with this amp/dac and HiRes headphones- well I am in heaven listening to music again.

I have no idea how this performs. I tried 2 different units and could not seat the tubes on either one.

It seems like a contradiction, doesn't it? To have Bluetooth connected to a tube amp...If the idea of vacuum tubes with a warm glow and a retro aspect appeals to you, this could be a good choice. Of course, there are a couple tubes in the circuitry, but if you look at the photo of the internal PCBs that I attached to this review (more later on why I did that), you can see plenty of modern SMT integrated circuits. I'm not sure if the entire audio signal path is vacuum tube, but I'm guessing not.Even calling this device a "preamplifier" is probably not accurate, in the sense that you cannot take very small analog signals (phonograph output, a microphone, etc) and boost them to line level.All that being said, again, if you like the idea of tubes, this is an attractive device to sit out for display, and it has a pleasant orange glow emanating from the area where the tubes are (mostly, it is NOT tube filament; it is supplemented heavily by some orange LEDs!).Pros:* sounds good, based on my listening tests* looks good* pretty easy to pair with Bluetooth devicesCons:* I heard hum in my headphones. However, when a song started playing, in the quiet introduction to the song, the hum went away, either completely or almost completely.* The knobs are tiny and difficult to turn, at least if your fingers are as big as mine.* The worst problem: it was VERY difficult for me to install the vacuum tubes. I think they came with bent pins. I tried straightening them, but I was operating blind, essentially, because you can't see down into the socket to evaluate which pin(s) are causing the problem. I tried removing the decorative copper-colored rings to allow me to see better, but that didn't really help (and the rings are quite difficult to remove, and to re-install).Eventually I disassembled the amp so I could see what the installation problem with the tubes was. By doing this, I could see which pins were not perfectly matched to the socket, and after bending a few of them, I was able to install the tubes. Of course THEN I had to pull them back out so I could put the whole thing back together. Afterward, because the pins were now straight, I was able to install the tubes, with some difficulty. This is NOT fun, and you should decide if you're ok with hassling with the tube installation. I think better sockets do exist, which guide even slightly bent pins into the receptacle, but these sockets are not those. You need almost perfectly straight pins, and you need to be perfectly aligned, before you can push the tubes into their sockets.Overall I'm thinking I would regret purchasing this if I had paid the listed price at the time I ordered the amp. However, in the end I have an attractive, good sounding "display piece" that some people may really enjoy using.

El equipo reproduce exactamente lo que promete , sonido claro decodificar muy bien y como preamplifier funciona de maravillas

This preamp sounds as close to the source as I have heard.I hooked up the output RCA's of this Preamp to my Onkyo AV Receiver. I then A/B listened to the same track playing from the original CD compared to from my FiiO High def Bluetooth player sending this thru this DAC. I had them staggered about 20 seconds so I could listen to the CD, then switch to the DAC and listen to the same 20 sec. At full volume on the DAC and my FiiO the volume matched perfect to the CD player. I listened to this on some Infinity Qb 10" three way speakers. The sound was as perfect to the CD as I could hear. Same impact, detail, presents, and spaciousness.The bass and treble controls worked well, as with the volume knob. Switching between inputs worked well. I like the weight, it is heavy enough to stay in place and not move all around either by operating it or the cables pushing it around. The looks are good and they have matching components to keep the same look for your setup if you choose.My only complaints, and they don't affect sound so I didn't take points off for these.- My thumb doesn't fit between the knobs, so when rotating Bass, Treble or Volume, I ran into my thumb getting in the way and I would need to stop and adjust my grip.- One tube went in fine but it literally took my 30min to get the other tube to go in. The tube pins were flat on the bottom instead of being rounded, and the socket has flat edges to the top of the connectors. I had to bend the pins carefully with small needle nose pliers until I had them perfect before the tube would go in.- Power cord too short. The cord won't reach any outlet from any surface you're going to use this on.Why can't these manufactures give you a 6ft cord, I would gladly pay the extra .10 for the extra wire.Overall a really great sounding preamp/DAC.