Description
4-Channel Stereo Headphone Amplifier, 1/4″ Connectors
Compact Control Unit
Stereo Headphone Output Level Adjustment
Independent Channel Rotary Volume Controls
(4) 1/4” Stereo Headphone TRS Output Connector Jacks
1/4” TRS Source Input Connector Jack
Power On LED Indicator
Power Supply Included, DC 12V/150mA
Dimensions (W x D x H): 4.07” x 1.18” x 2.24”
If you’re tracking more than one musician at once, or if everyone in a group wants to listen to a playback, you need a monitor distribution system. The compact, flexible PHA40 can power up to four pairs of headphones and up to four independent volumes. Grab this super-compact amp during your sessions to power practically any headphones–four of them at the same time, to be exact. This allows four people in your studio to listen to the main mix while recording and each listener can determine their own volume level using the dedicated output level controls. The PHA40 contains 4 high-power stereo amplifiers that maintain the highest sonic quality even at maximum volume levels. These ultra-low-noise operational amplifiers are included for outstanding audio performance.
From the manufacturer
Compact Control Unit
- (4) 1/4” Stereo Headphone TRS Output Connector Jacks
- 1/4” TRS Source Input Connector Jack
- Power Supply Included, DC 12V/150mA
- Dimensions (W x D x H): 4.07” x 1.18” x 2.24”
- Weight: 0.99 lbs.
4-Channel Stereo Headphone Amplifier, 1/4″ Connectors
This compact Headphone Amplifier can hold 4 high-power stereo headphones & maintain the clarity of sound even at maximum volume levels. These ultra-low-noise operational amplifiers are included for outstanding audio performance. It allows up to 4 people in a music session to listen to the mix making each capable of adjusting to their volume level preference.
- Uses High-Power Stereo Amplifiers for Superior Audio Quality
- Stereo Headphone Output Level Adjustment
- Independent Channel Rotary Volume Controls
- Power On LED Indicator – Stereo Headphone Output Level Controls
J-Sigmo –
I think I know why we see varying reviews of this ampI read a lot of the reviews of this little amp before buying a couple to try out for myself.What struck me about the reviews was that there were a lot of people who gave the unit five stars and were completely satisfied with what you get for the very low price. But then there were quite a few one-star reviews where people said that the amplifier didn’t actually amplify the signal at all.There were also various reviews in between those extremes, and complaints that the 1/4″ TRS jacks were unreliable or mis-sized such that you couldn’t get reliable contact or even had to have the plug inserted partway into the jack to get proper stereo.Further, this amp was, naturally, compared to the very similar Behringer HA400 also sold here on Amazon:
Behringer HA400 4-Channel Stereo Headphone Amplifier
Many reviewers were perfectly happy with the Behringer, but found the Pyle to be substandard or completely useless for their application.I already had one of the Behringer HA400s and have been using it for several years. But I needed another similar amp and figured I’d give the Pyle a try despite the higher percentage of negative reviews. (The Behringer also has some negative reviews, but they’re easier to dismiss for reasons I’ll get into further on).Many of the complaints common to both the Behringer and this Pyle are about poor contact with the 1/4″ TRS jacks that both of these units have. My experience with the Behringer has been that because I am using it with headphones and an input cable that use 1/8″ TRS plugs, I had to purchase adapters to make the transition between the two sized connectors.I tried two different brands/makes of adapters and found both of them to be completely worthless. They were intermittent at best, sized incorrectly on both the 1/4″ outsides and their 1/8″ insides. It was extremely frustrating to say the least! You’d have to hold the headphones’ plug at some angle and pull it out slightly to get it to make contact. Or in some cases there was no way to achieve contact. It was shocking that such adapters would even be sold, for any price, no matter how low.I finally ordered some adapters from Parts Express (another seller here on Amazon), but I had to go directly to them because these adapters were not an item that they sold here (at least at that time). The ones I got there have been flawless. They fit the amplifier perfectly and they fit the headphones and my input cable perfectly as well. And they make good, solid, reliable contact with zero fiddling.Since I got those “good” adapters, I have had zero problems with the Behringer amplifier. And it’s done its job very well.I think my application is a lot like many people here have described. I have a cable running from our home entertainment system back to the couch where we usually sit when watching TV or listening to something, and the little headphone amp is there, in a console in the couch, and we have several sets of headphones plugged into it so everyone can set their own listening level. Mostly, my wife and I use this setup when we’re watching or listening alone and don’t want to disturb the other person when they’re sleeping, reading, listening to something else on their tablet, etc.And most people doing this will find that their headphones and whatever they’re feeding the amp with will NOT have a 1/4″ TRS plug on it. So they’ll need adapters. So I attribute many of the bad reviews of both of these amplifiers to the adapters that many of these people are probably using. I know I had burning heck with this issue, but I knew that it was the fault of the adapters because I also had some “real” 1/4″ TRS connectors that mated perfectly with the amp itself.Of course, it is possible that people are getting amplifiers with poor 1/4″ jacks. So I can’t dismiss all of the bad reviews entirely as it really being bad adapters, but, after my bad experience with several different adapters, I suspect that’s the problem with many of them.So now we move on to the poor reviews of this amp that claim that the amplifier doesn’t actually amplify the signal. And you get clipping before the headphones are putting out a loud enough level.I have disassembled and traced the circuitry for both the Behringer HA400 and this Pyle PHA40, and drawn up schematics of what’s inside.I was sort of surprised to find that the circuits are virtually identical! Someone reverse engineered someone else’s OR this is a “cookbook” design found in one of the semiconductor manufacturer’s datasheets for the OP amp that both unit use (the ubiquitous 4580 dual op amp).The ONLY difference between the two is that one unit uses a 22pF compensation cap from the output to the inverting input of each amp section while the other unit uses 20pF caps. That is purely a matter of that value being more readily available, I’m sure. It would have an almost unmeasurable effect on the performance – the difference is probably less than the tolerance of the parts, actually.Seriously. The circuits are the same. The same OP Amps, the same, exact topology, and the same values of each and every component.BUT… And this is what I discovered in my Pyle unit that makes me think I’ve found the reason for the “this amp has no gain” type reviews.In both the Behringer and the Pyle, a 47 Ohm resistor is placed between the output pin of the amplifier and the connection to the headphones. This introduces some isolation to protect the amplifier and help assure stability with a variety of loads. These little Op Amps don’t really have enough output current capability to properly drive low impedance headphones. They wouldn’t be my choice for a headphone amplifier output stage. But they’re inexpensive, and this setup does work, even if it’s not really the ideal way of doing things.And a lot of other things aren’t ideal about this design. But remember that you’re getting a four output headphone amplifier with enclosure and wall cube for between $16 and $25 depending on the one you choose. You’d be hard-pressed to buy the enclosure, connectors, pots, and other components, let alone the PCB for that money. So we’ve got to keep in mind what we’re dealing with here.Anyhow, the circuit boards in both units have the component values silkscreened onto them. In the Behringer, the actual values are shown. In the Pyle, the “codes” for the values are shown (this probably makes it easier for anyone assembling the unit to get things right even if they aren’t trained to know what those codes found on the components actually mean).In the Behringer amp of mine, these output isolation resistors are, indeed, 47 ohms. But in my Pyle unit, even though the PC board is silkscreened with “470” (which, being the code for the value actually means 47 times ten to the 0 power – or 47 Ohms), the components actually installed are all marked “471” which means 47 times ten to the 1st power or 470 Ohms. And, indeed, when measured with an Ohmmeter, they are actually 470 Ohm resistors.Now, unless someone changed their mind about the design after they laid out the PC board and put “470” on the silkscreen, this is an error. I’ve got output isolation resistors that are ten times the design value!Now, ideally, any amplifier driving a speaker will have as low of an output impedance as possible in order to have good “damping factor”. Damping factor is really the ratio of amplifier output impedance to speaker impedance. And what this tells you is how well the amplifier will be able to control the motion of the speaker cone. The higher the damping factor, the better. We want the amplifier to be able to impress its “will” upon the speaker. The lower the amplifier’s output impedance, the more accurately it can control the voltage appearing at the speaker terminals and thus, the current through the speaker voice coil, and therefore, the motion of the speaker.When the amplifier output impedance is high with respect to the speaker impedance, the speaker is more free to move on the basis of its inertia. A speaker is a device that converts current through a coil into movement. And the speaker cone and coil assembly always has some mass. Further, to move air, it must create force with which to push or pull on that air. None of this can be done accurately if the amplifier’s output impedance is high.The 47 Ohm resistance is bad enough. But having 470 Ohms in that position is ten times worse.Further, as you might imagine, with ten times the output impedance, the amplifier will be very hard pressed to deliver much voltage to the speaker if that speaker has a low impedance. The combination of this output resistor and the speaker impedance (speaker in the headphones) creates a voltage divider.Let’s say we’ve got a set of headphones with an impedance of 8 Ohms (yes, they exist). The voltage delivered to that 8 Ohm speaker will be 0.0167 times what the amplifier IC is actually trying to put out! So right off the bat, you’ve only got about 1/60th of the signal level! Of course, even the 47 Ohm (correct) resistor will be creating a divider that is cutting you down to about 1/7th of the voltage that the amplifier IC is trying to put out.Now, if we’ve got a set of headphones with a higher impedance (as is often the case), then this voltage division will be proportionally less. So people who use this amp with higher impedance headphones may not notice any problem. The unit delivers enough voltage to the headphones to operate them well enough.Of course, another variable is the efficiency of the headphones. Some may not require much power to deliver quite high sound pressure levels to your ears. While others may be very inefficient and require a lot more power to deliver that same sound pressure level. So the impedance along with the efficiency of the headphones someone uses with one of these amplifiers will play a large part in how they perceive both of these amplifiers. But especially if they get one of these Pyles, and it has the 470 Ohm resistors installed.I’ve got a pair of Sennheiser HD201 headphones that I use for TV watching. These are not high-end phones. They’re just what I use to watch TV. I’ve tried them on both the Pyle and the Behringer, and I got adequate volume level out of them on the Pyle. I’m sure I had to turn it up a bit further, but it was acceptable. These headphones are rated at 24 Ohms, with a sensitivity rating of 108dB SPL. Headphones are rated for sensitivity (efficiency) as the sound pressure level achieved with 1 milliwatt of power delivered to them.Now this gets a bit complex because the impedance of the headphone speaker will enter into the equation to determine the power delivered to that speaker for any given voltage applied across the coil. And this all interacts with the output impedance of the amplifier to determine how loud any given headset will play with one of these amps.But the simple version is this: If you have high sensitivity and high impedance in your headphones, you won’t be bothered by the 470 Ohm resistors. The lower the sensitivity and impedance, the more likely you are to find the 470 Ohm output impedance of this amplifier to be a problem.Also, I don’t know if someone changed the design of this Pyle amp and didn’t change the silkscreen legend on the PC boards, OR if the one I (and perhaps many others) got was actually manufactured incorrectly, and it’s really supposed to have the 47 Ohm resistors in that position, the way my Behringer does and the way the PC board legend indicates my Pyle SHOULD have. Beats me, but it seems like a manufacturing error.There are other complexities to all of this as well.In both of these amplifiers (remember, I said the circuits are identical) they use a 100 uF capacitor to block the DC path from the common (sleeve, negative) terminal on each headphone jack from system ground. This cap is, therefore, common to both of the stereo channels. It saves them four capacitors per amplifier over the more traditional capacitor coupling method of using one capacitor on the output of each amplifier channel. But it also introduces some crosstalk at low frequencies between the two stereo channels. Whether you can hear this or not is questionable, however, because we tend NOT to get much location information from low frequencies anyhow, and that is, for example, why you can get away with a single subwoofer in a system. You really don’t care where those low frequencies are coming from because you can’t really tell anyhow. So this is a sneaky, yet clever way to save some money.But the real point is kind of strange. Because you’ve got a 100uF cap in the signal path, you’ve introduced a high-pass filter into the system. But the amount of filtering will depend on, you guessed it, the impedance of the headphones to some extent.And somewhat ironically, using the 470 Ohm output resistor actually lessens the effect of this low pass filtering. The amps that have these “undesirable” 470 Ohm resistors may actually deliver better low bass than the ones with the 47 Ohm resistor because the effect of the capacitive reactance of this small cap will be less of the total signal loss in the systems with the higher value output resistors.But, of course, on the flip side, you’ve got far worse damping factor, so the bass may be more prominent yet less “well controlled”.Anyhow, there’s a lot to all of this, and the things I take away from all of this are:These are NOT audiophile amplifiers. But they’re not intended to be. They’re meant to do a job and do it for cheap.The complaints of no or little gain with these Pyles may very well be due to a manufacturing error where they’ve put 470 Ohm (marked 471) resistors in the output circuits of some or all of the Pyles. Or the manufacturer may have done this on purpose, but that seems like a bad idea. But in either case, this may well be why we don’t see those same complaints of “no gain” in the reviews for the Behringer units.These amps are incredibly inexpensive. And I’ve gotten great use from the Behringer unit of mine. Now that I know that the circuits are identical, but my Pyle has what appears to me to be the wrong value of output isolation resistors, I may well solder in what I believe to be the correct 47 Ohm resistors in my two Pyles so they’ll actually be identical to the Behringer which I’ve enjoyed for several years.Doing this will obviously void any manufacturer warranty, but really, on a $16 device, do I care? Plus, I know the design works and is reliable with the 47 Ohm resistors in place because my Behringer has worked flawlessly for me over these several years that I’ve had it. And I leave it on 24/7. So the complaints about these units not having a power switch seem a bit silly to me. The wall wart is likely going to waste more energy due to losses in the cheap transformer even if you DID switch power off at the amplifier anyhow. So either way, if you’re trying to save the earth by switching one of these units off, you’ve got to unplug the wall cube anyhow. I’m too lazy for that. Besides, the “waste” heat all goes into my house anyhow, and its COLD outside right now. So it’s not wasted at all. :)I know all of this discussion is going to bring out the desire among us audio nuts to modify these amps to make them sound better. And I fully understand that urge. But I’m not sure I’ll do much of anything to mine other than put in the “correct” value resistors in the outputs. If I was going to build a good headphone amp, I wouldn’t start with this design, or case, or power supply… So I kind of think this is one of those instances where ignorance is bliss. And leaving well enough alone might make more sense.Then again, I also fully understand the urge to do just a bit of “tweaking” of things to eek out a bit better sound.The photos I’ve attached show the bottom of the PC board out of the Pyle. One is the overall shot, and the other a close-in crop showing one set of these “incorrect” resistors with the 470 legend silkscreened onto the board but with the 471 resistors installed.Again, the silkscreen for all of the other components on the Pyle PCB show the “code” for the component value. So even though the board says “470” and has a 470 Ohm resistor installed, this still appears to be an error.
Audi0he4d –
Not Feeling it.This is going to be a live review typed while I listen through The Pyle-Pro PHA40-A. If you dont want to read it all, just skip down to the CONCLUSIONMy setup to get the fairest most balance review that I can is to take my laptop through a Roland Duo-Capture (USB) and then run a patch cable from the Duo-Capture to the Headphone Amplifier. All volumes on the laptop is maxed and the Duo-Capture are set at 75%. The Pyle is set at neutral (with knobs at the 12 oclock position)My Test Playlist is: Safri duo – The Bongo Song, E-Type – Campione, The Irish Symphonia – Feet of Flames, Haiku D’Etat – Non Compos Mentis, Sponge – Plowed, and Queen – We Are the Champions.The Heaphones I am using in this test are: Grado SR125, A&H Xone XD-53, AKG K701, and Beyerdynamic DT770’s.The first song starts off and I am wearing my Grado’s. The Bongo Song is pretty much all drums. but there isn’t enough power driving my Grado’s to make it pop. The XD-53s work well with this song even though they tend to require more power. I am not noticing a particular loss of sound quality but the volume is softer with the open pack cans than with the close back cans. The 701’s are miserable to listen to on this one. Very little definition from the song and the huge soundstage of the cans make it sound even smaller, the DT770’s require the most power to drive but are still at a good volume.Campione, a techno song is again soft in the Grado’s and the 701’s, the Xones are getting some distortion without volume change but the DT770’s are awesome on this song. They are right at home.So far no clicking or any jack issues as reported by other reviewers. Also so far Im noticing that closed back headphones are definitely at an advantage. I am not playing with the volume knobs at all.Feet of Flames, heavy on the strings is okay with the Grado’s. Soft, but thats expected. Not muddy, but not brilliant either. On the Xones, the sound is a tad darker than the Grado’s but without the driving baseline all I get is a higher volume than the Grados. The 701’s… Oh wow! The definition and clarity is amazing. Yes its softer than the Xones, but each note is carried, each instruments voice and tones are captured perfectly. By far this is the 701’s favorite song through the Pyle. The huge soundstage is loving it and really sounds great. The Beyerdynamics are loud. Louder than the XD-53s they are flat sounding and I get my first blip in the sound. Im not sure if thats the small laptop clipping or having problems keeping up with the dataflow from this high bitrate song. The volume is appreciated through the DT770’s but it doesnt have the clarity that the 701’s did.Non Compos Mentis is hip-hop. As expected the DT770s and the 53’s are louder than the Grado’s and 701s. Its just subpar on all the cans.Plowed is a standard rock song. Its not well known but is decent. The vocals are coming through no issue with the Grado’s. Im hearing all the instruments and the song is shining but I wish the volume was better like the Xone’s, which are louder but dont carry the clarity. The 701’s arent any better, in fact they are softer than the Grados. Much better clarity than the 53s. The DT770s again strike the best balance between volume and listenability, but even then there isnt enough juice to power more than the mids on this song.Queen starts off wonderfully in the Grado’s. There is a great punchiness to this song despite being softer. This is the best song so far for the Grado’s on this setup. The Xone’s are good with this song too. The thematicness of the song comes through well. Its also softer than other songs but better than the Grados but not by much in the loudness section. The 701s enjoy the song but the Grado’s still are better. There just isnt enough umph from the Pyle to make the headphones really sing. The DT 770’s are the loudest on this song but dont treat it nearly so well as everything just runs together and creates a kind of muddiness. There is a buzzing sound too with the upper registers of Freddie Mercury’s voice that wasnt present in the Grado’s like the amp really cant push as much.Now for more of a test. Im using the Grado’s for this in the #1 jack. As I adjust the volume knob, the levels change smoothely with no clipping. I get distortion at the top end as the headphone drivers can’t keep up. Queen sounds great! Playing with the volume knob I get the Bongo Song to come alive, but as I move the levels around I lose clarity with volume change. The Pyle really likes the higher volumes over the lower volumes and as I move into another song I have to find the sweet spot for that song for the best listening to the song to strike the right balance between loudness/volume, clarity, depth, brightness, etc. Its definitely better than neutral but I loose so much as I lower the volume that there are definitely more changes than just volume as I turn it. Im not exactly pleased with that. I get all the songs to really come through but now for the next test.I bet you were all wondering why I included the Duo-Capture huh?Well, I unplug the Pyle from the Duo-Capture and plug the Grado’s into the Roland. First off, the volume is much better than anything I was getting out of the Pyle (granted 1 headphone instead of 4 but still…) and I get much better clarity. The songs pop. Feet of Flames is inspiring, Non Compos Mentis is not perfect but is much better than the sad mediocrity is sounded like on the Pyle. The Bongo Song is roughly about the same but with more bass hz input and sounds more well rounded. Campione sounds more like the game-score it is than something roughly thrown together While Plowed comes through with such great guitar that there is no comparison to how it sounded on the Pyle. Queen comes in again softer than the other songs, but that probably more due to the recording. As I adjust the volume on the Roland, all that changes is the volume. And Max volume is still loads louder than max volume on the Pyle.CONCLUSIONThe Pyle PRO PHA40-4 is most definitely NOT a headphone AMPLIFIER but is does make for a decent powered headphone SPLITTER. I would expect an amplifier to better drive large driver headphones and provide more volume than the originating signal on its own does. I expect a headphone amplifier to provide the same audio quality and (for lack of a better term) “features”. I want to hear the same song the same way no matter where I position the volume rheostat and the Pyle just doesnt provide that. Granted not alot of people will know, but this is something that I would put in the guest bedroom or take to work and not worry about.REDEEMING QUALITIES: Price – Its CHEAP compared to others. It does not require batteries. Its small. And people who haven’t really compared it to much else wont notice what its lacking.MY ADVICE: Get something else for yourself. Spend more money and get something that sounds better. FIIO’s E9 (or E1 for that matter) or an ART, or Creek or Topping or something that isnt THIS. And Yes, I gave it TWO stars mainly because its price and having a powered headphone splitter could occasionally come in useful.The Pyle Pro PHA40-4 is in the lower right corner of the picture next to my laptop.
KC –
Adds the necessary boostWorks as needed, affordable with small form factor. Might be a bit awkward if all four slots were actually used without headphone cord extensions. We only use two and it works great.
Bob L. –
Works well and simple to setupPerfect for what I needed. Simple, reasonable amplification, and working out of the box in under 2 minutes. Couldn’t ask for more.
Big Orange Wookie –
Headphone Amplifier… NOT a Speaker AmplifierI have to start off this review by addressing several of the one-star reviews that this device as woefully underpowered for their use. Most of them have apparently tried to connect this device to speakers, which it will not be able to drive at all.This is a **headphone** amplifier and when used as such it will be more than loud enough. If you need a speaker (or PA) system, look at other products. This is only for people wanting to boost and/or split their headphone output.Now, I agree with one-star reviews if you have a channel (it tends to be channel #1) that only provides static when used with headphones and there are a couple of those reviews out there. Luckily, all four channels on my device work flawlessly. If I lose a channel, this review (and the star rating I give it) will be adjusted accordingly. That being said, I’d still give this about four stars with a channel not working because I don’t need four channels… I only need two. Anyway, on with the review.BOTTOM LINE – A great little device that amplifies stereo input for headphones (AND) allows you to split the output into four seperate stereo channels, each with it’s own volume control.NOTE: This plays very nicely with the Hosa MHE325 Female TRS 1/8-Inch to Male TRS 1/4-Inch Headphone Adaper Cable (25 ft, ~$10) which allows you to position the box where you need it (i.e. near the TV) and gives you extra cord to reach across a room. You’ll want one of these cables per channel (unless you want to use a splitter at the end)Pro’s- Powerful & Compact- Single-Channel Input to (up to) 4 channel (HEADPHONE level) output- Individual volume controls for each channel- Price- Solid construction- NOT battery poweredCon’s- Bright Red LED- Always OnReview: I purchased this, like a lot of other reviewers to amplify sound from our television’s audio out port to headphones.We were using a long cable with a series of adapters and a splitter so we could have two sets of headphones and listen to the television quietly after the kiddos were in bed. Since our TV output is RCA, we needed to convert that to a 1/8″ (female) stereo plug and then add in a splitter. Since the audio on the TV was a “line-out” port, we had no control over the volume and it was just barely loud enough to hear anything.I eventually got frustrated with not hearing half of the conversations on our favorite programs and began to look for a full receiver that had a headphone output on the front that I could use. I really didn’t cherish having to drop a couple of hundred dollars on a speaker system I’d hardly use.I stumbled across this item by chance and decided at the low price point I’d give it a shot. I was very pleasantly surprised with the outcome. The box is very small and well constructed. It’s very powerful (only needed the channel turned up less than a quarter of the way to hear it very loud and clear through our headphones).My only real complaint is the little red LED on the front of the box is so bright, it distracts when the lights in the room are out and we are watching TV. I used a small piece of black electrical tape to cover it up and it’s much better. Another minor gripe is the fact that there is no on-off switch so it’s always on… but since my DVR is always on, this is a minor concern. We also plugged ours into our surge protector (which is highly recommended when working with sound equipment).All in all, this is a wonderful little device that will definitely work nicely as a headphone amplifier and channel splitter. If you are need of something like this… Pyle has you covered.If you are looking for something to power speakers, don’t buy this. Look for a good PA system instead.
Tim James –
High Output ImpedanceI actually wanted to use this as a pre-amp rather than a headphone amp. Before I did anything I plugged some ear buds (low impedance) into the device and like others have mentioned, the output is less than just having my earbuds plugged into the source. This is surprising since the device is listed as a ‘headphone amp’. To me, that means it should have sufficient gain and output impedance to drive MOST headphones louder than the source. Earbuds are not headphones, but still.I got out my scope and measured the output impedance at a few frequencies. Came out to around 470ohm which is surprisingly high considering most headphone manufacturers have been edging toward lower impedance units. Sure, 650ohm headphones still exist, but I feel like the lower impedance models are more common now. If you’re an audiophile who uses quality headphones you probably are familiar with damping factor and you can see how this cheap unit will never achieve even 2:1 damping factor, let alone what is generally considered optimal (4:1-8:1).This unit is a clone of any of the 4 channel headphone amps you see, like Behringer for instance. It uses cheap 4850 opamps. It appears that the input signal is boosted by a factor of 10 and then each channel has it’s own opamp set to a max of unity gain with the pots. If you run the pots to max, the opamps clip to the lower rail and you will get distortion.Assuming you run the channels at 80% or less, the distortion figures are pretty good. I saw some variations in gain over a frequency sweep from 20-20k, but nothing crazy. Impedance was solid across the same frequency sweep. Based on my analysis, if your headphones are anything below 100ohm, you can only consider this a splitter with independent volume control. It won’t amplify anything. Higher than 100ohm, you will get some amplification. Whoever has complained about mono vs stereo doesn’t know what they are talking about. It’s a stereo unit, it uses dual channel opamps all the way through.I’m giving it 3 stars because it’s supposed to be a general purpose headphone amp and without explicitly stating the high output impedance, it’s going to disappoint a lot of folks with 32ohm headphones and it will never achieve a ‘good’ damping factor with any headphones. It also shouldn’t clip to a rail at any pot setting. It actually works great as a cheap turnkey pre-amp assuming you are feeding a high impedance input to a secondary amplifier. Also, if you’re comfortable soldering, definitely open the case up and check the TRS connector solders. Mine were not well flooded which inevitably will lead to those solder joints failing with the stress of plugging/unplugging.
Alan K. Lohr –
Well built and excellent soundThis is the 2nd headphone amp I have purchased. It is simple to use and the construction is strong so it will last a long time with care. The volume controls are easy to use. I highly recommend this product!
J. Harmon –
Awesome AmpSo far I have only tested with one of the line outs but I will be testing the other soon with additional headphones and cords. Quality is outstanding, I compared several headphones on output 1 and compared with a Polk Surround Bar, even modest over the ear headphones sound as good or even better then the 300$ Soundbar. I feel the quality of the amp is more then adequate as the audio sounded rich and clean to my ears. Obviously headphone quality varies dramatically and I tested with the Sony MDR ZX300 my old ISymphony Noise Cancelling and the Seinhesier HD 201. The change in headphones was very interesting to pick up the small differences in the similarly priced headphones. I thought the bass response on the Sonys was nice but I like headphones that fully enclose the ears to block out noise, amazingly scenes with thunder and base were very good, better then the subwoofer was producing. Surprisingly the Sonys were not bad for the price still I expected a little more based on the reviews I read. To get much better performance you need to likely spend at least 70$ and I would love to test the Sony 7506’s at some point in the future.Back to the Amp, it serves its purpose well, volume only needs to be at 1/3 for the Sony headphones to be loud, plenty of power for all the Cans I tried. Looks nice and volume controls work well being on top. You will likely need 1/4 adapters as this unit takes full size plugs. Really no complaints for the price, I needed an amp to go from my Digital to analogue converter so I could get audio of my TV on headphones, this way the kids can sleep and I can use my new Plasma to watch some movies at night. For now I’m outputting from my Sony Bluray player which has a Coax digital out while I wait for my optical dual output adapter to arrive. Once that’s in I will be able to have audio on the sound bar and headphones at the same time from all inputs to the TV. Figured it was better to go dual output then use a Toslink switch. Its surprising to me that some TV’s now only have a single digital optical output.Anyways to sum up, for 17 bucks you get an amp that powers four sets of headphones from a single 1/4 stereo jack source, just make sure to buy some adapters and long cords or hook up your wireless headphones and you should be all set. I imagine this unit would also work well for labs and you could also further split with y adapters, I did this briefly so I could compare two headphones side by side, you will need to obviously crank the volume up though if your driving two sets of headphones from a single jack. I imagine ear buds would need very little juice to power, mine were all over and on the ear sets and had plenty of power from the amp.
Stan –
perfectAOK
R. McDaniels –
Good product, but made in ChinaOnce in a while, China makes a good product. This is one of those times. I needed something to boost my headphones for clean, clear, close, remastering work. These headphones sound great. They do get uncomfortable after a while, so I slip them off, take a break, and then come back. But they really do sound great, and seem sturdy too.