2PCs ULBRE 3.5mm Male to Male Audio Cable 3.3ft Red Audio AUX Cable for Car Stereo, Smartphones, Speakers, Tablets

For an inexpensive tube amp this thing is the bomb. The sound card in my PC was never loud enough, and I often had a hard time getting audio loud enough. With this I rarely have to go past 1/2 volume. Technically the amplification isn't all boosted by the tubes. Inside there is a MOSFET and I believe it contributes to the amplification. The tubes are amplifying the audio as you can hear a ping sound if you tap on the tubes with a fingernail or coin. There is little to no additional hiss/static/white noise and it doesn't seem to add any unnecessary sounds or distortion. I like it enough that I will be purchasing another soon. Can't complain about the build quality, I've opened it up and the circuit board, chips, resistors etc are all nicely soldered, and I expect this to last for years.

First, yes, it does drive inefficient/mid-impedance cans (my Beyer 880 250ohm) loud enough with the stock tubes. There's good and bad about this amp and the bad can largely be turned into good.After lengthy breakin with the original parts, because it's so inexpensive, it really gets 4 stars. But if you do the couple of inexpensive upgrades to it I suggest, it's a 5-Star Item because, again, SO cheap and it can perform very nicely. Is it ever "perfect?" No way, but it's darn good!!!Bad first: It sounds tubby, loose and furry. It gets better with breakin (100+ hrs) but the cheap Chinese tubes are just not good except for one thing: They aren't very microphonic, implying sturdiness. Highs roll off, they're glassy and hard, midrange is pulled back and furry/blurry, and the lows are bloated and sloppy. But, overall, a fun sound with not-so-hot headphones with soft highs. It will growl a bit, something tubes do. The power supply works. New tubes take a few plug in attempts to get it to kick over. Plug in the power to the supply and THEN the supply to the amp. First time took me 3 or 4 attempts, got the "clicking" til then. The LEDs come on when it's fired up on plugin. The LEDs are way too bright. If they were red or orange, I wouldn't mind so much. Some people may like that. I want to see the tube's heaters glow! The power supply and cord emit a lot of noise. Arrgh. Stretch it as far from the amp as you can, including the AC line. At volume down all the way, it picks up noise galore including a local radio station. When you turn it up even a little, that all goes away. Hmm. Crappy pot? Power on back, you can easily bend the mild steel pins in the plug so be careful! The in/out jacks on front seem okay enough, board mounted. The tube sockets are mounted raised up on their board pins. Why? It gets hot! Class A and tubes gets hot! Don't sit this on a painted surface. Pwr supply okay, though, has rubber pads. Amp has no feet, just smooth metal bottom. Don't put it on your lap or a cushion. It needs to be able to cool. So those are the bad things: sloppy lo-fi sound, picks up rf noise with volume down, gets hot, noisy pwr supply, LEDs too bright. This is my assessment after 120 hours of breakin.The Good: It's made pretty well and simply overall. 4 screws tension the whole thing together. Simple! Pull the tubes, undo the screws and it falls right out into your hand. Fiberglass board. Good. This is a hybrid amp. Tube input buffer and op-amp outputs. That's fine. The TI op-amps ARE worth replacing with the tubes. First I was tried tubes. Easy, no open case upgrade. Got Raytheon Military 6AH6WA (ruggedized) and they were really thin and tight. After 20 hours, they started to blossom and became punchy and growly in the bass and much clearer overall but still a bit rolled off in the highs. Quite pleasant/fun. After about 120 hours, very nice, affordably cheap and easy to find. Next, I tried Raytheon 6AN5WA military rugged tubes and those are the best, by far. Clean, much more extended highs, nicer midrange up front and articulate swingy bass. But it was still kinda harsh overall. So, noticing that the op-amps are in dip sockets, and after someone else asked about changing them, I did some research. Op-amps have come a long way since these very well regarded but too "clinical" TIs hit the market. Op-amps are super clean but can be TOO clean and have no romance to them. That. So instead of the latest/greatest at $20 for a pair, reviews kept mentioning a Burr-Brown OPA2134PA as a drop-in replacement that sounded "musical" and "lively" and "smooth." They're usually about $6-8/pr. They drop right in. I found an eBay seller with them for 5 for $5 shipped. Done. I didn't expect much difference. I was wrong. They are much smoother and the bass is growlier. There is (with the 6AN5WAs) a bouncier, much smoother and yet clean sound that's plenty loud. Didn't solve the noise with the vol off, but it made this little sucker sound NICE.So, bottom line, spend $10 or less on a MATCHED pair of Military vendor 6AN5WA tubes (or take your chances with Russian tubes for more) from Raytheon or GE and another $5 on a pair of the BBOPA2134PA op-amps and ka-pow! HUGE difference in sound that you'll like a lot! Talk about bang for the buck! And the lows will be good enough, even off FM, that you won't wish you had tone controls most of the time, and the highs will only be crappy when the source is. This will be good enough with a modest pair of good phones like Grado SR80s that you'll be able to tell the difference in sources. Nice little steal for the money, once you change out these two parts, which, I suppose ARE the amp, but you're going from poor, mismatched parts to nice ones.I haven't looked at the volume pot. I may go with a more linear pot so it has more control at the low volume end.OH, and this could make an interesting distortion box for guitar! You'd have to make custom cables to allow you to go into one channel, feed that output to the other channel and then out, all in mono. Not tough to make. So, gain and then gain. Could be a very cool fuzzbox for cheaps, and you might even want to use the stock parts for their harsher sound! Again, cheap!Have fun and remember to break in tubes with MUSIC, actual music. Just turning them on does nothing but mess them up. Enjoy!

The amplifier is 5 stars, but the power supplies I received are 1 star, as received. The were slow starting or did not start. The power supply is also mislabelled. It is not +/- 24 volts, but closer to +/- 12 to 18 volts. The 6.3 volt filament voltage is 5 volts. I had two power supplies, that would intermittently start or not start when plugged in. After taking them apart, and looking up the switching regulator I.C. on the internet, I found that there was no starting resistor for the I.C.. How any of them worked, is a mystery. I connected a 100k ohm resistor from the I.C. Vcc terminal to the main board HV supply +, and both supplies now start instantly. The 5 volt filament voltage requires further modification, which would require a schematic. It would be very difficult, because it is surface mount components. I'm afraid to dig into the amp, for what I might find, but it seems to be a better design. I am using it to drive a couple of old 8 inch Radio Shack speakers directly, if you can believe it, with enough volume.

First off the good. This little amp sounds great and is a great value. Really made my Grados sing, much better than the native amp on my phone or laptop.The negative. It really needs a power switch on the front or back, the only way to turn on or off is to pull the power. It would also be nice if the input was on the back just to keep cable routing a bit cleaner. Finally the ability to disable the blue LEDs that light the tubes so you only have the glow from the actual tubes would be nice.Not the fault of the amp, but I tried to use this on a laptop dock at my desk and got a 60hz ground loop hum from the laptop when both were plugged in to AC power.