Little Bear BK 6N11 12AU7 6922 Tube valve Headphone Amplifier

the unit is good and the sound to. but, there is a little bit of adjusting when you get the unit ( probably not all but it is a possibility.
 
the tube glows but the LED that is located under the tube is so strong that they override the light from the blower in the tube. i have modified mine, solder the led’s off the unit and placed them in a place where they do not light up anything. 
the tube is a standard, so easy and cheep to replace, you should always have one backup! 
 
when you receive the unit is comes with a PSU that is not good for good audio quality. it is cheap, not much filtering and has a constant 50Hz rumble. 
you should invest in a LED POWER SUPPLY i use this from eBay item nr. 321999561547. it is a 24volt PSU unit i recommend 3 amp so the unit always has good amount with power.
when the power supply unit got replaced with the led power supply the sound quality got better, and the 50Hz rumble is gone. 
 
Why i give 4,5 star 
 
The value: for the unit is okay,  there is few changes that would make the unit better, that do not increase the price.
 
Audio quality: is good for hobby usage, if you need a amp for you’re headset for gaming, movie and music. but if you own a studio or edit sound files you should get something else, because it is some noise coming from the transistors.
 
Quality: is great, but some changes that would make the unit a lot better. 
 
Design: the placement of the plate on top. that hides the circuit and has a hole in the senter from the tube makes the heat become trapped and when the unit heat up a lot, more noise comes trough the audio out.
 
NOT FOR PREAMP FOR OTHER AMPS! ONLY HEADPHONE!

Just doing a quick review of this amplifier that I got from China. If you look at my other amp reviews, you'll see that I have tried the Alpen E17 which I thought was underpowered and had an average DAC making it a total waste of money, and that I also tried the Objective 2 which wasn't underpowered, but wasn't something I would call powerful either.
 
Please note I tested this with a $14 bulb I purchased off of Ebay, an RCA model. So I'm not using the bulb it came with although I didn't listen to see if that made a difference.
 
Well this thing is SUPER powerful. To listen to it without hurting my ears, I have to set the source's volume (my laptop headphone jack or my phone headphone jack) to like 5-10% and then I set the volume on this to about 25%. This would almost certainly make my ears bleed if I turned its volume to the max and turned my source volume to the max. So it does the most basic thing an amp is supposed to do: deliver as much power as you could possibly want. It's rated at "450mW" based on the ebay site, but it doesn't say what impedance this was measured at. It does say it can handle a 600 ohm headphone, though, so perhaps it was 450mW @ 600 ohms, which would make this quite a powerful amp. I wish I had an HE-6 to see how much power this can really put out.
 
It also does its job in delivering bass and warm frequencies. I don't know if the tube is doing anything; but the sounds do sound slightly warm and aged, i.e. it makes it sound like what you might hear from an old jukebox or stereo system..
 
I also hear very little line noise and it's easily ignorable (you have to really listen for it), although there is a lot of loud cracking (probably due to its power) when you plug and unplug the source and there is a little bit of cracking noise as you turn the knob to adjust the volume.
 
Overall, though, due to its very low price, its high power, its decent sound and its ability to let you enjoy a tube amp for a measily $45, it deserves 5 stars. I think I would recommend this over the objective 2 amplifier, for example.
 
Last thing. At first, the sound in the left side was louder than the right, by a lot, but there are two orange screws near the tube that you can adjust to fix this.