Perfect for My needs in a small JAMM'IN studio

Theres a loud ... like omg loud pop when you plug into this thing. The sound is ok and connectors are good. I use it when im tracking other people because im not paying $ to do this task. Wish mackie would bump up the build a little because in my opinion, its worth $

I would wager that anyone who is not experiencing prestine sound from this device does not have it connected to their line outs. I use a dual TS to TRS cable and I connect each TS end to Line Outs 3/4 and the TRS end to the Mackie HM-4 headphone amplifier input. What beautiful sound! If that doesn't work then you either using bad cables, a not so great audio interface, not so great headphones, or you have a defective HM-4. This is an incredible product and you certainly get a great product for the price. Word of caution. This device does not have a limiter so you should be very disciplined in checking and double checking your volume levels BEFORE powering on your gear. In hindsight, I think this is how I blew out my previous headphones but didn't realize it at the time. DO NOT CONNECT THIS AMP TO THE HEADPHONES JACK OF YOUR AUDIO INTERFACE. I have seen this done before, which means not all negative reviews are fair or justified, in my opinion.

This little amp was just what I needed to add to my mixer for headphone applications. Works great.

More solid than expected for the price.

My "meh" observations are not big deals:
- It feels like there might be amplification when the dial are right of "mid" and that amplification might be noisy, and if that's what's going on, maybe an indent at "mid" could be useful.
- The AC adapter feels like an afterthought.

Beyond that, great, no complaints, nice potentiometer feel. Knobs are on tightly which is probably good for most, although I can see a case for wanting to customize the knobs.

Holes for the heads of screws might have been nice, as would a clip for the power supply cable. It's built like a rock, but if it falls then the power cord falls out.

Small and portable, I use it when I take my laptop and gear out to capture tracks for my recording projects.

Great little piece of kit. I work at an art museum and we use these at each of our video installations. Makes being able to hear dialogue in narrative films adjustable for everyone's needs. We often see hundreds of users over several months and these have held up extremely well. Great sound, built to last!

Works great, small and plenty of gain!

This is a simple sturdy design that just works. I needed it for a 250ohm headset and it gave me plenty of volume. Without the HM-4, I had to turn the volume up to near max to hear the details. Now I just need to turn them up about 1/4 volume to get the same results without the hiss. The extra ports are a bonus. Now I do not need to switch out my headphones between closed back and open back. Very nice addition to my studio setup.

Was looking for an inexpensive way to hook 2 headphones up to my little SSL2 interface. I primarily use this little setup to go on location to record a vocal or instrument to bring back into my main studio for editing. Works as advertised.

I don't use multiple headphones all the time, but the occasions I need them, I'm glad I have this. Good quality for a good price.

Does the job admirably and doesn't break the bank.

One of my outputs got real finnicky and doesn't always wanna work very well. Lots of crackle. But, it's a pretty solid headphone amp if you need some extra juice for yourself or wanna connect multiple pairs of headphones to a single source.
I don't regret buying it. I've used it an awful lot.

I was looking for this headphone amplifier since long time ago. It's well made, the knobs feel decent, looks great, the green led is not awful at night, it works as intended, the box and the way it comes is perfect. I don't have any complains.

I'm using the headphone amplifier on the headphone output of my Focusrite Solo interface, with a BOSS BCC-3-TRA cable (1m long). For now, it works great.

I keep it around for utility in a pinch. If you are looking for a pristine signal path, save your money and look elsewhere.

This little guy gets it done. Small and easy to throw into a bag for travel sessions.
Can't beat the price for what you're getting here.

I wanted to write a review for this amp because I couldn't find one during my research for what I was going to use it for and hope it will help someone else.

I bought this amp to use exclusively for my Roland FP-90X keyboard because I felt the headphone volume was a little too quiet at max volume than I would like it to be. I connected amp through the front 1/4" headphone jack with a TRS male to male cable. When I connected to L/Mono output on the back of the keyboard, only the left volume would come through. I am not sure if a dual 1/4" to a single 1/4" would work since I didn't have that cable on hand. I am using a pair of Beyerdynamic DT 770 PRO 80 ohm headphones and they sound great with this amp. I keep the amp about about 3/4 volume and don't hear and hiss or background noise and now I only need to turn the volume up on my keyboard to about half and it loud and clear. I am happy with my purchase.

As other have mentioned, there is no power switch for the device and you have to unplug it when not in use. I recommend doing what I did and purchasing a "DC Inline Switch Manual Inline DC Power Switch Extension Cable Male to Female 5.5mm x 2.1mm Barrel". This will make it so you now have an on/off switch and not have to keep unplugging it.

I bought this to use with my headphones while playing my drums with Drumless tracks.
It has worked extremely well!

Awesome item. Makes recording much easier. Very cool

I've been using the HM-4 for about 3-4 months now and absolutely love it. Its super friendly on the wallet and it does exactly what its supposed to do. The only thing I don't like about it is there is no On-Off switch, so you have to unplug it when you want to turn it off. Not really a big deal or even something to gripe about, its super easy to unplug so I can understand why they didn't include an Off switch. It would just increase cost. So if you're looking for a headphone amp to use with your 220 ohm headphones or you just want individual headphone control for multiple people (or even just yourself, which I have several different types of headphones for monitoring and producing) I would HIGHLY suggest this for any bedroom producer. I can't speak for professional studios as I just have experience with my home studio, but I love it.

The HM-4 Headphone Amplifier does an outstanding job of boosting the audio highs and lows from high quality headphones and earbuds. Tested with DT 990 Pro headphones and Shure 215 earbuds, and they both produced crystal clear audio. Input Connections: 1 x 1/4" TRS stereo (unbalanced) Output Connectors: 4 x 1/4" TRS stereo (unbalanced) Input Impedance: 10 kOhms. Output Impedance: 47 Ohms. These specifications were more than sufficient for my needs as a novice music producer.

Great little headphone amp at a good price does what I need it too do, well built I would add.

This headphone amp work great does what I needed it to at a good price

Works as expected

The Mackie HM-4 is a wonderful headphone amp, perfect for tracking with multiple musicians. I bought one for a session I did with an acoustic guitarist where we were recording live vocals, acoustic guitar, and drum machine. The HM-4 worked perfectly, allowing us each to have our own individual headphone volume. I did not notice any coloration to the material we were monitoring and I hope to have my HM-4 for a very long time maybe forever.

I am using this to monitor the stream between FOH, monitors and live strem feed. It is a very quick and accurate way to split the tasks between these functions for the 2 engineers.

40 bucks for a nice little headphone amp? 4 channels and small enough that it doesn't take up a lot of room on my desk. Very happy with this one.

The HM-4 amp is a great little unit, allows me 4 sets of headphones with individual volume knobs. It's small, sits well next to my ATEM Mini Pro switcher. A tough black metal case, feels heavy. Clean sounding as well with my AKG 240 MkII headphones. No regret on buying this box.

Works as advertised, good quality.

Bought this item based off reviews saying it was very quiet regarding background hiss. The one that I received is not quiet at all. Every output has quite a bit of hiss. I would recommend going with a different manufacturer.

We are running a podcast into a rack-mount I/O and DAW but needed a headphone mixer to go on the table so everyone could control their own level without us having to go into the control room or communicate with the sound operator. Works great!

Headphone amp works great for my recording. Couldn't ask for more for the price.

I have a pair of Beyerdynamic DT 990 Pro 250 ohm headphones. This gives them the needed boost in levels that I like. Plus when I mix I like to test the mix in a few different headphones. This allows me to keep a few hooked up at once instead of having to plug and unplug from my interface.

Rest unit and affordable

Works great in my home studio.

I have a pair of Beyerdynamic DT990s. Due to 250 ohms of impedance, you need to power those bad boys with a little extra juice. i.e. you need some kind of headphone amplifier to bring a little extra electrical power to the headphones. this HM-4 does the trick. it's built well, feels sturdy and solid.

4 stars because the only way to turn off the power is to unplug the power cord, though some reviews mention purchasing a third-party switch to control the power.

yea, so far, I highly recommend it as a headphone amplifier for your cans that have high impedance (>60-70 ohms)

*be sure to have a TRS 1/4 inch cord to run from your preamp to this HM-4, then you plug your headphones directly into the HM-4.

*there will be a pop if you unplug/plug your 1/4 inch cable, so always have the headphones off, the volume down, before you put your phones on.

I share a headphone feed with the drummer in his studio. His hearing is better than mine so I bought the HM4 to boost my signal. It works fine but I had to buy a 1/4" TRS patch cord as all the inputs and outputs are 1/4". For the price point,it's fine.

This amp solved my problem of not getting enough volume through my Focusrite Scarlett 212 interface headphone output. These small interfaces are know for this low output. The Mackie booted the gain 3 fold. However, I didn't like the somewhat hollow sound I was getting. But once I was hooked up through Zoom and/or Source Connect the sound improved to be normal. Go figure! I don't know why but... it's working well to my sat now! And ya can't beat the price!

Many people including myself were disappointed to find out that the HM-4 doesn't have an on/off switch. An easy solution to this problem is to get a DC inline switch. Search for Manual Inline DC Power Switch Extension Cable - Male to Female. This adapter will provide you with an on/off switch without having to unplug the power supply to the headphone amp. The adapters are marketed for use with LED lighting, but work perfectly with the HM-4.
I hope this info helps anyone who's frustrated with this issue concerning the HM-4.

Very nice and doesn't take up a lot of space. Had to replace my second Presonus Monitor Station in a hurry

Product is perfect for what I needed. As always Sweetwater has the best customer service I have ever experienced. Matt Masek is awesome.

Wayne J.

It s built well it works fine at $. It doesnt have an on/off swithch which would have made it a 5 star rating. Its a drag to plug and unplug everytime.

Nice small headphone amp. I don't need a big piece for my system and read the reviews on this one and ordered it. Fits the space that I have and works great for me. Nice price too.

Fantastic sound - good bang for the buck! No on/off switch though - but big deal!

After nearly a year of using this headphone amp, I really dig it. Running a TRS stereo cable from the main headphone out from my Tascam DP24SD into the headphone amp allows me to place it anywhere around my setup and I can adjust the volume levels with ease without the need to frequently adjust the volume on the DP24SD. With 4 headphone outs, this headphone amp is idea for 3 other band members (and/or anyone else monitoring the jamming & recording process) to all hear the same audio which they can tweak the volume knobs to each listener's desired volume preferences.
I'd highly recommend this headphone amp.

I really love this machine. It was as simple as connect the cables and enjoy! Cannot beat the price.

I have a small home studio and needed to use multiple sets of headphones for multiple musicians. This was an affordable option and so far it has worked great. It's so cool for everybody to have their own volume control. Make sure you get a TRS cable to connect it to your headphone jack properly. The only minor downside is that there is no on/off switch, but I always unplug all of my equipment when it's not is use, so it's really not a problem for me. I am really happy with this purchase and Sweetwater is awesome. Jerrod, my sales engineer, is also very cool.

Does what it's supposed to do and does it well. For my home studio, I needed something for connecting multiple headphones and this does the job. An inexpensive way no solve my needs.

Very nice well built

I use this when I record on my Tascam Portastudio. I got tired of plugging my headphones
into the back of the Tascam, and having the wire resting across the unit getting in the way
of things. I also use it when I'm recording another guitar player, and we can both listen
to the track being recorded simultaneously.

I use the Steinberg UR242 interface and it's headphone output wasn't powerful enough to push the volume on my Beyerdynamic DT 990 Pro 250 Ohm headphones to satisfactory levels.

This is where the Mackie HM-4 amplifier steps in. It provides the much necessary boost to the headphones signal, while keeping the response flat and without any imperfections that I could notice. It's very transparent and can be used to monitor up to 4 different headphones at the same time!

Another amazing quality product by Mackie that I'm seriously impressed with.

As usual, Mackie came through again with a quality product! My mixer only provided one headphone outlet jack, so I expanded it to a four using the Mackie HM-4. The unit is built well and the sound through it is nice and clear! It is so much fun to able to share the MIX using headphones!

This product is easy to set up and use and has allowed my sports broadcasting team to hear each other clearly while monitoring the broadcast via our mixing board output. It allows them to concentrate better on what each other are saying during the broadcast and that enhances their delivery during our football broadcasts. Nate Kaufman with Sweetwater was awesome to work with and provided this solution suggestion when I described what we needed.

This headphone amp is heavy duty. Just like I've read, it is built like a tank. Solid piece of equipment!

Home studio with multiple headphones needed more volume. This did exactly that. Very happy.

I bought this so I would have independent volume control of the backing tracks that I practice guitar to. Really impressed with this product. The build quality is excellent and it is dead quiet. Exceeded my expectations especially considering the price.

I've been putting together a "backpack" recording kit for songwriting sessions and such. The interfaces I use has one headphone out and obviously this is a limitation as there is usually two if not three of us with vocals and instruments. So this seemed like an ideal add. Sturdy construction and very small footprint - two of my requirements. As others have mentioned you'll want a TRS cable for connection from your interface HP out to the unit. Sounds great and has plenty of amplification. Pleased with it so far.

This device works perfectly at a more-than-reasonable price. It's quiet, no background noise whatsoever, and the tonality coming through the headphones reflects the sound coming off of my JBL studio monitors exactly. No need to spend a fortune, I highly recommend this unit.

Works great, but no on/off switch.

Very sturdy and overall well built. Knobs are solid and precise.

Nothing much to say. It's plug and play and does the job well.

This device worked well for my needs. Super rugged & EZ to set up. I bought it for recording my band. Only one headphone out from the recorder. The guys in the band love the individual volumes. Nothing fancy but well built & great for the price.

I got this simply to allow multiple people to have monitoring capabilities and it does allow for that. The jacks seem a bit cheap, not so much like they will break but I have to really force in the headphone jack for it to seat all the way. There is also no power switch, so I am thinking about installing a toggle myself as it seems primitive to plug in and unplug an electronic device just to turn it on and off.

I was never concerned about perfect sound quality (and so I did not pay that close attention to it), I got this so multiple folks can hear the mix when recording. If it came with a switch and had just slightly more cooperative output jacks, I would give it 5 stars for the price. As it stands, it is definitely usable, there a just a few minor additions that would have made it much nicer (like a power switch).

I can't say I know a lot about headphone amps as this is my first one, slowly getting into the audiophile world with a set of Audeze LCD-2 open-back headphones and Subpac MK2.

It's a pretty simple product, 4 headphone channels so I can connect my Subpac to one and my headphones to another. I had to get a multi-channel amp because I was reading that the Subpac should be on its own channel, they're just two 8" subs so I didn't want to crank them too high. The headphones go up to a 70 ohm impedance which is perfect for my bedroom studio. I know some go up to 100 or more but that's unnecessary for my use.

The amp really nicely allows me to get full potential from the amazing drivers in the LCD-2.

To clarify, the unit has a stereo, unbalanced input.

The online documentation refers to "balanced" input, which implies mono TRS (hot/cold/ground). The online docs even showed a pin-outs diagram of a balanced mono input.

The included info sheet says to "connect a balanced or unbalanced line-level signal" to the input, and in the specs section refers to the input as "Female 1/4" balanced-unbalanced".

I used to think of Mackie's docs as useful, even with the corny jokes here & there.

The unit works fine; but this is perhaps the most important thing you need to know about this device, and they got it wrong.

As a side note, I like that all the connections on are one side. Makes it easy to squeeze into a tight little spot.

It works great I wish it had an on/off switch however.

Works Great , Thank You !!

Works and sounds great,especially for the price! BUT make sure you have a trs cable to connect it to your mixer, etc. An instrument or speaker cable will not work. You use one of those, you will only have sound out of one channel!
There picture shows the HM-4 with a trs cable (notice the two rings!)

Coming out of the headphone out on a FocusRite 2i2 into the HM-4. HM-4 is feeding headphones, and ear buds. Sound quality is the exact same as coming straight out of the 2i2. The HM-4 has plenty of headroom, and the unit is dead silent when there is no single. Partial to Mackie, have Mackie equipment that was purchased in the 90's, and still working flawlessly.

I play keyboards for my church's praise team. Recently, my wife hosted a women's event and we had some guest musicians play with us. We use a digital mixer with in-ear monitors. We don't have any extra monitor units, so I bought the HM-4. The guests all hooked to the HM-4 and had my mix in their ears....and at their own volume. It functioned exactly how I was hoping it would. Plenty of clean power with no distortion. We use a click track, so anyone trying to play along with no in-ears would be lost. We also run stereo (because this isn't the 60's) and everyone was able to pan themselves to which ear they wanted (via my monitor unit) for more identifiability. Having this unit in my setup is invaluable when needing additional headphone outs.
I love the construction of the HM-4. All metal, not a metal base with a plastic housing. The volume pots are clean and solid. No hiss or scratch. Great unit.

This unit does NOT have an on/off switch...Didn't know that when I bought it. I may decide to open it up, and install a small toggle switch..if there's room. Otherwise I have it plugged into an extension cord...which I keep the receptacle end close to the unit, and just plug it in when I need to use it. Otherwise it does what it's supposed to do.

The tiny and inexpensive Mackie HM-4 is great when you need to drive up to 4 sets of headphones at different volume levels. It's designed to be driven from a single unbalanced stereo signal on a 1/4-inch TRS plug (not dual line-level balanced outputs). Each of its (4) stereo outputs can produce an output of approximately 180 mW into 50 ohm phones, or approximately 220 mW into 32 ohm phones. Voltage swing is limited to about 4.2 volts RMS into high-Z phones.

Although there are no mute buttons, each gain pot can fully attenuate its output to fully mute that channel. Unity gain (0 dB) occurs at a pot setting of "12 o'clock" (mid-point) and there is approximately 20dB of additional gain available by turning the pot farther clockwise from its midpoint. Channel tracking is good from the midpoint up, but can vary slightly at high attenuation settings. Distortion is low enough that the clarity and "openess: differences between HD-350's, SRH-940's, MDR-7520's and HD-650's are preserved and are clearly audible.

This amp can drive virtually any contemporary mid to low Z phones (16 to 100 ohms) to dangerously high levels. It has very low distortion as long as the input is not over-driven, and has flat frequency response above 40 Hz. The is some slight roll off (2 or 3 dB) and phase shift of the very lowest frequencies starting at about 35 Hz. but that will only be noticed when using phones with flat and extended bass response. At gain settings above about +10dB there is some slight "hiss" audible on high-efficiency phones, but that is typically not an issue in normal use.

One note: If you are driving this amp for a relatively "hot" headphone output (like that on some Sound Devices recorders or Mackie mixers), be sure that the input signal is kept to a level that is comfortable when driving phones directly from the source. If you have to set the HR-4 gain pots for much attenuation (settings lower than about "9 o'clock" you are risking overloading the inputs and may also experience some channel balance mistracking. The HM-4 seems to work best when it's gain post are set between 11 and 2 o'clock.

I picked this up for the Sennheiser HD 650 cans that I just got and they seem to push them pretty decent. Did a comparison with audio from just my Audio Interface directly and then the MC-4 and could definitely tell the difference. Like the size of the unit and the overall design is good.

Cons (minimal)

No power button
Wall wart is rectangle so in order to plug it in to a power conditioner you have to use one of the outside slots.
Feel they could have designed it a little better in this area.