The first product that I received was evidently a returned item . After powering the unit up I immediately noticed very audible static present in both channels but more pronounced in the left channel . The static faded after about one hour of operation . The static reappeared after approximately ninety minutes .
I followed the extremely vague instructions for adjusting the bias voltage for the tube . I have many years of technical electronics experience with amplifiers as a hobbyist . The bias voltage is difficult to set precisely with the tiny, low quality potentiometers , but I attempted the adjustment despite the shortcomings . There was a difference in sound quality but I was unable to resolve the static issue .
Amazon was excellent in working with me to return the defective product free of charge and I actually received the refund as soon as UPS accepted the parcel to be returned .
In the meantime , I ordered another Bravo Audio V1 and received it in two days . The new amplifier works quite well without any of the problems of the initial unit .
After two days of using the amp with the Russian tube that came with it , I replaced the tube with a new General Electric 6922 with gold pins that was manufactured in Great Britain . This new tube made a remarkable difference in sound quality .
These little units run hot so longevity of the semiconductors is suspect . I have a small fan cooling the amplifier continuously during use . Vacuum tubes take heat in stride but semiconductors have an abbreviated lifetime when exposed to excessive heat and insufficient heat sinking is used .
I hope to enjoy this amp for a long time to come.

Arrived defective.

This amplifier arrived defective. But I took it upon myself to repair it rather than return it. It at the very least provided me with an interesting learning experience, diagnosing and repairing it. (It was simple, open circuit across a resistor.) Between the time I ordered this amp, and repaired it. I ordered a Schiit Magni 3 as a replacement.

The audio just does not provide for me what everybody is raving about for this little amp. At least, not compared to the Magni 3.

Both amps were tested with the built in DAC of an Audio-technica AT2020USB+ and a pair of Audio Technica AD700X's. (Notoriously anemic on bass and low end.)

The Magni 3 is a fairly warm amp to my untrained ear. It tames the brightness of the AD700X's remarkably, it makes the mids and highs so wonderfully textured and clear. But it fails to drive any additional bass out of the headphones.

The Bravo V1? It is extremely warm. It drives a considerable amount of new found bass to the AD700X's. But... It muddies everything else to do so. The mid's and highs just don't have any texture of definition to them with this amp and headphone setup.. Nor does the V1 drive the power the Magni 3 does.

Very disappointing, lots of hype for this little guy. While it did work fine the first couple times I used it with my Senn 600s, the sound certainly wasn't anything special; acceptable I guess. Third or fourth time and the amp would have these silent spells lasting a minute or so. Finally, after one week of having this handsome looking little thing it died completely, refusing to turn on. Boo this device.

As a guitarist who plays through stereo vintage tube amps and having a wife who has this insane idea of sleeping at night. I found this tube headphone amp a blessing compared to the incredibly bad sounding digital portable amps commonly available. The only caveat I have is the RCA board mounted connectors are not sturdy enough for constant plug and unplugging. There are better styles available that are more resilient but this isn't designed to travel around in your gear bag. Having said that the sound quality is so much better I will never go back. Be aware that the 1/8" input jack will bypass the RCA connectors but is a better choice for repeated cord in and out. I use this after my effects pedals and the impedance matching works great. No more tinny cheesy practise headphone amps for me!

I am not, by any means, claiming to be a connoisseur of audio fidelity, but this is an exceptional and affordable little gadget that truly makes a difference to your listening experience. There are some minor things that I wish would have been better but for the price point, I am not complaining. This is an affordable tube headphone amplifier that will just about power any headphone and truly change the way you enjoy music. I would listen to music directly through the device itself (phone, pc, etc.) but this adds a general pleasantness to the overall audio coming from the headphones and speakers (you can use it as a preamp as well). I am using it with my turntable and Audio-Technica M50s. Overall I am satisfied with the purchase.