I am connecting this to a small mixer to split the headphone output to four headphones for band practice. Read reviews of comparable spitters I was concerned about sound quality deteriorating. However, in my experience this split delivers a quality signal with good sound clarity and a great boost. Dialing the volume halfway has easily been sufficient. No on/off switch but really not a an issue for me. Very pleased with this purchase.

I love this! It is nicely made, feels good and sturdy in the hand, the knobs feel sturdy. You need one of these if you want to listen on two (or more) pair of headphones to the same source. A splitter does not work. (You might be able to hear it with a splitter, but you are stretching the power a small device can put out, and you will often get only one channel on each headphone.
I use this while teaching drum lessons so that I and the student can hear the same thing; metronome or music.
However, I have also taken to using it all the time by myself for just one channel because the amplified signal is better than straight out of the device, and it's also much nicer to use the volume control knobs on the HeadAmp4 and not have to touch the volume on the device (i.e. metronome, iPod, CD player, etc.).

P.S. Oh yeah, others have pointed out that there is not a power switch, so if it is plugged in it is always on, and the green LED is always lit. I conveniently solved this problem by plugging it into an outlet strip that I can turn off when I am not using it. Plug anything else that you use along with it into the same outlet strip (e.g. my metronome), and then it becomes very convenient.

This product is really a great deal, sounds good, no distortion or buzzing or anything i could detect, even when you crank it up. Its very solidly built (metal case); the design is nice too. I've been using it nearly everyday since I got it, it's been holding up great.

*Just a note: this is an amp only...so that means it is only good for volume increase and more appropriately powering outputs than the originally source might.

My only complaints are small:

-all the jacks are in the back (can kink cables if they are ultimately fed forward; can be a good thing if you don't want a mess of cables showing on your desk)
-no power switch (I don't really care though, I just leave it on for the most part)
-the knobs are little too close to each other
-power supply is chunky, can block other outlets

Not much else to say, if you are looking for a solid headphone amp on the cheap side, go for this.

UPDATE 4/28/19:
I have been using this every day for just about 9 years now. It still has held up and I am very happy with the purchase. Some of the painted on letters and numbers have worn off in places, but it still functions like the day I bought it.

My laptops sound card is finally breathing a sigh of relief. I have been using Panasonic full size phones, among others for quite a while. But the Panasonics are my primary phones because they are so comfortable since installing pearstone deluxe velour earpads. Aaah, pure heaven.

Back on topic, you cannot imagine the difference with this amp. The sound just opens up, I hear nuances in the sound that weren't so clear before. Now I'm talking about full size phones, which are generally more power hungry. So with the Headamp 4, your laptops sound card can do what it's better at. Putting out clean Hd sound instead of powering your phones. This amp gives you fantastic range and headroom, absolutely no noticeable hiss, noise, or distortion, x 4. Super clean pure sound.

I looked at the Rolls HA43 4, but i didn't like the slider volume controls on the top, dust eventually works it's way in, then you're dealing with static. I prefer the precision of the rotary volume controls, and the I preferred the clean look of the headamps front panel, and the inputs on the back. Let's not forget ipods and other mp3 players, which are incapable of driving full size phones, or multiple earbuds, to their full fidelity.

To sum up, the Headamp 4 is built like a tank. The construction, except for the 4 plastic knobs, is all heavy gauge black anodized aluminum, it is weighty and substantial, no lightweight junk. The finish is professional with nice graphics. All of the controls and inputs are clearly marked and easily readable. And it sounds fantastic. This is one purchase I'm 100% satisfied with. Highly Recommend. This isn't something you'll use for a little while then toss aside. You will use it.

*A side note. 2 weeks ago, this amp was $49.95 one day. The next day, $65.00. What the hell? Was there a tsunami where the Headamp factory is that I didn't hear about? I got lucky when I checked "other buying options" and found a seller with 1 in stock for $45+$5.50 shipping. This is something I've seen a lot on amazon. Wild price fluctuations. This amp is so good, I believe it's still the best you'll find for $65.00.

My application is splitting the fixed level, recording output from a stereo receiver into 3 external, independent volume controlled zones -- Kitchen, Living Room and Breakfast Room. Plus, I will have an extra channel to power a pair of wired Bose noise-canceling headphones with a 3.5mm plug and no need for an adapter. For this project, I also needed 4 sets of 1 meter cables with 1/4" TRS male split to RCA stereo jack pairs.

The Art HeadAMP 4 quietly feeds a Parasound HCA-1206 six-channel home theater amp to create three stereo pairs. Each channel has an input gain which allows for setting channel balance and maximum volume. Volumes are running around 10-11 on both the HeadAMP 4 and power amp to give plenty of listening volume with no perceivable noise or distortion.

The master stereo receiver in the study has PC soundcard, Logitech Squeezebox, AM/FM and CD inputs. It powers a 2.1 HSU audio system with the receiver's volume-adustable pre-amp outputs going to a powered sub. My wife or I can select a different source to feed the recording output (multi-zone) than what we're listening to in the study, which is sometimes needed. The power amp is only turned on as needed to power 1 or more zones.

Previously, I was using a passive speaker splitter box, but was not happy with the sound, and the inability to set different volume levels for each zone was frustrating. Plus, I was on my 2nd unit, and like the 1st even more expensive one, a speaker would sometimes cut out and I would have to jiggle the selector button several times in and out to get both speakers working again. When I decided to add the 3rd zone (Breakfast Room), I re-purposed the old Parasound home theater amp for this multi-zone use. The speaker splitter box is now a paperweight (like the first one).

The Art SPLITmix 4 passive splitter/mixer might have worked OK, but for only $15 more I opted for the HEADamp 4 to ensure good output levels and the bonus to power a pair of headphones for quiet listening. Headphone distribution boxes by Behringer, Mackie or Presonus would probably have worked OK for less, or more money in the case of Presonus. However, I preferred the Art's front facing controls, left to right channel 1-4 orientation and expected quality (from past experience), so chose it over the others. I should mention that it has a rubber edge that runs along each side to firmly grip the surface, keeping it from sliding around when I adjust the volumes. Nice!

Also, I should mention that Art did NOT respond to my questions about using the HEADamp 4 for this application, which was disappointing.

Enjoy the music, however you listen to it, but please don't play it too LOUD. You only have one set of ears, and they are definitely NOT indestructable!! Cheers.