Little BearLittle Bear B4-X Portable Dual-Mono Vacuum Tube Headphone Amplifier; Mini Balanced Audio Headphone Amp B4 Upgrade Version

I received the Little Bear B4-X and was extremely satisfied... for the first 16 days. During that time I used it a total of 11 times, adding up to 30 hours of listening time. I was keeping careful track of the number of hours and paying attention to how the unit's sound would change after a "burn-in" of 100 hours. The shortest listening session was 1 hour and the longest 5 hours. As I said, I was extremely satisfied and the sound was great. The fact it wouldn't run with passive power/while charging was only a minor annoyance and I was more than happy to just use it when charged... until yesterday, when after a listening session it simply wouldn't charge at all. After using it and plugging it in to charge the charger is no longer showing a continuous red light while charging, but instead blinking red/yellow. I thought maybe it was normal because it had been the longest listening session I did, totaling 5 hours so I left it charging overnight and the behavior never changed. When I tried to use it today it won't power up at all and when plugged in again it is still blinking red/yellow. As it also doesn't work while plugged in I am now left with a useless paperweight and major disappointment. If the company, seller, or Amazon makes it right I will update this review accordingly....and so I am. I was contacted by the company, who stated they believed it was an issue with the charger & not the LittleBear, asking if I could test it with a different power supply; I didn't have a suitable one at home, so went to a battery store and attempted to charge with a demo unit of a multi-voltage charger, set to the right settings. Still no charging. As soon as I relayed this info they informed me they were sending me a new unit, which arrived in record time and was again working flawlessly - but I was hesitant to immediately update this review, as the issue with the first unit showed up during "stress testing" as I was "burning in" the unit. Proceeded to burn-in the unit for a full 100h and have listened for another hundred or so since. The new Little Bear is performing admirably and sounds even better after the burn-in. Completely satisfied with the product and their customer service.

DAPとヘッドホン・イヤホンを繋いで音楽を楽しんでいます。通常タイプのヘッドホンアンプは、けっこう買い揃えてありましたが、あのちょっとリバーブがかかったようでぬるい音響を自分のコレクションに取り込みたくて購入しました。艶っぽい中音域が伸びやかであり、透明感もあっていいですね。バッテリ駆動時間が十分とは言えないので、お出かけのお供には足りないですが、お部屋使いなら問題はないでしょう。初期には時折ノイズが乗ったりしましたが、使っている内になくなりました。真空管らしい音響が気に入ったので、ローテーションに積極的に入れて、オーディオ生活を豊かにしています。

So far so good. Sound is warm. But long use sometimes started with rattling or humming sound.

Contrary to the information given in their q&a section, this is NOT shipped with an Australian power supply. Don't purchase if you need this. I now have to go through the extra expense and inconvenience of getting a 3rd party PSU because they can't put accurate information on their advertising. I expect more from Amazon, or is that typical?

I bought this amp 4 months ago more because It was a unique idea. Portable tube headphone amps are something that I didn't think existed and if they did they would be at least much more monetarily.I have not upgraded the opamp yet to the Burson Audio which was suggested by another buyer but it really stands by itself as it is as a great audio product.The fit of the audio cable is important from the source to the amp but they provided a pretty nice beefy short cable with the amp.So far using a Pioneer Hires player, Sony AW55, and even my LG V40 thinq in Airplane mode with its 4 DACS and very good audio section the B4-X was solid amp quiet and works well with offboard DACS as well.Having been a musician for many years and also a Progressive Trance DJ I have put it through its paces with my BeyerDynamic Dt1350s, Tesla T1, Focals, and IEMS from my Westone 4Rs to 5 Driver IEMs. It provides solid power to drive up to 300 ohm over the ears without an issue. Pair it with a good outboard DAC and it is really a great unit.For 99$ it punches WAY ABOVE its class. It was so good I bought a second one and sent it to my Brother so he could use it with his Audeze and Hifiman Planers.I look forward to swapping out the OPAMP to see the levels that I can drive it to.In a world of expensive electronics that don't deliver the Little Bear B4-X is really a steal.What started out as a "OKAY was looking at a Schitt Valhalla to listen at home but a Portable tube headphone amp!!!????? I gotta give it a whirl" turned into a great little tubeamp which is much better than the price or printing on the case shows.