Monoprice Unity 200-Watt Bridgeable Power Amp - Class‑D Amplifier, 12-Volt Input/Output Triggers, Rack Mountable

So I've actually bought 3 of these over the last few years. #1 I used to power a pair of atmos speakers with a 12V trigger line to turn it on from the AVR. #2 I used in the living room to drive a pair of bookshelves for casual listening using using the signal autodetect. The pass through RCA inputs go to a sub. #3 I used in my home office to drive a air of bookshelves using the signal autodetect. Maybe they aren't "audiophile" quality, but they have good sound even when using them at fairly loud volumes. The power on and off works reliably both with the 12V trigger as well as the signal detect. There is a "volume control" adjustment on the back of the amp meant for adjusting peak volumes more than anything else. I'm not sure if it really adjusts the output or just attenuates the incoming signal, but its mandatory to tweak it when using the signal detect function for power on. In my office, when I'm listening to music at a low volume while I'm working the amp would occasionally cut off due to the small input signal on quieter music. So adjusting the volume on the amp down about 30-40% means I can run the input at a higher volume level to make sure the amp stays on while still keeping the speakers at a reasonable volume level for background music. And even though I'm giving up on max power, the amp still drive my 89 dB sensitivity bookshelves a lot louder than I want to listen in my office so practically I'm not losing anything. Runs at fairly minimal heat and even after some spirited use in the living room where its mounted inside a cabinet with the door shut its not hot enough to worry about. I think its a good power level and feature set at this price.

I have bought two of these to replace a different power amp with A/B/A+B switching that proved to be very lacking in power output, nowhere near what it says in the ad, even when driving just a single pair of speakers. My two Monoprice Unity 100s will be used to drive a pair of speakers in the ceiling of our dining room and a second pair out on our covered patio. For this type of service where you really don't need hundreds of watts or audiophile performance they are ideal. If you think you're getting audiophile performance from a Walmart priced (but I assure you not quality) product, think again. If you want more watts for your Atmos or rear surrounds or whatever, I would think about the more expensive 200 model, however. First of all the likes: 1. Price - at $125 and change these are excellent value for money for use as a modest power amp for, say, Atmos speakers or, as I am using them "muzac" service around the home. 2. Built quality - very sturdy cases, nice and solid, well finished. 3. Size - very low profile and only half the width of a standard hifi box or AV receiver, meaning you can put two side-by-side in your stack without taking up too much headroom. Rack mountable too with brackets supplied. 4. Heat (or lack of it) - being class D amplifiers they don't create a lot of heat, which is good. Things I don't like: 1. Volume knob on the back - might be okay for "set it and forget it" use, but for balancing speakers out it may be an issue for some. There's plenty of room on the front panel for a volume knob, I can only think hiding it on the back meant they could use a cheaper one (see below). 2. Volume knob is very small and needs a screwdriver to turn it. 3. Volume needs to be cranked up all the way anyway so why bother? 4. Speaker connections - you have to strip the wires and insert them into a block, tighten the screws down. The blocks will only take 14 awg wire at most, and you have to be careful not to let stray wire strands short out the connections - they are VERY close to each other. I have to reconnect my wires for a different reason this weekend, and I am going to take the opportunity to "tin" the wire ends with solder to give me solid ends to fit into the connector block. Sound quality? Jury's out on that one. To be fair I'm hardly using a pair of top-of-the-range hifi speakers, just modest built-ins, but I'm not expecting audiophile quality from a $125 amp either. Should be perfectly fine for Atmos or rear surrounds or muzac service though.

I am using this item to power the rear high surround speakers in my Dolby Atmos 7.4.4 setup. Yes I have 4 high speakers, 2 front, 1 center, 2 surround, 2 rear surround, and 4 sub-woofers (1 in each corner of the room). Powered by Onkyo TX-RZ920 9.2 4K UHD Atmos receiver. The 2 extra rear high channels are fed from the pre-out jacks, and that's what drives this Monoprice amp. In case you are wondering, 2 of the sub-woofers are part of my front speaker setup, configured as full-range. The other two sub-woofers are connected to the Onkyo sub1 and sub2 outputs. Many people do not realize the incredible difference that balanced subs can make. Now, back to the Monoprice amp: It is so well designed and configured. I like the fact that you can choose to have it auto power-on, or be triggered from the 12V trigger of the main amp. The unit is compact, sturdy and comes with heavy duty brackets for wall mounting or stacking. There is also the ability to bridge the amp, or to select 4 or 8 ohm output. The volume control is an almost hidden turn screw - great for this application - no chance to accidentally change the volume after you have carefully calibrated the whole system. The amp silently comes on when needed, and turns off some time after the music stops. Perfect. My only minor issue is that the speaker connector could be more robust. On the other hand, it is designed to connect all the wires to a single plug, which is very handy for installation and maintenance.

I am using this amp along with a wifi transmitter to have rear speakers in a room that can't have wires ran to the back. I have this hooked up to very efficient Klipsch speakers (RB-61ii) on each end of my couch facing me. There is a audible hiss that is emitting from the speaker horns, even with little gain being used on the amp. It does not have anything to do with my source or cables because even with the cables disconnected it still hisses. The louder the amps gain is turned up, the louder the hiss and it does get pretty loud. It is extremely annoying. To be able to get it to at least a tolerable level I have to have the gain on the amp turned to no more than 15-20% and have the rear speaker level signal output in my Yamaha RX-A3080 AVR turned all the way up to 10+ and the front levels down to -10 just to have the rear speaker volume be loud enough to level match without extra loud hissing. However, even at that point... I can STILL hear slight hissing, it is just barely tolerable but if I'm being perfectly honest it still bothers me. If you have efficient speakers, especially Klipsch, I would avoid this amplifier and get something with better quality. Also, I don't think they could have made the speaker wire connections any flimsier. When you are screwing down the speaker wire it feels like the whole thing could easily snap off.

It's pretty cheap and rack mountable but won't last more than a couple years in a commercial use. Last one went out in 15 months. We've burned through three of these and finally decided to upgrade to crown.

I'm using this to power 2 subs, bridged. It works as it should but there are a few things about this amp that annoy me, especially for the price. First thing is that I notice a pretty audible hiss from the subs, even at only 60% gain. It's only audible at super close range, so it's a non issue for subs but if running speakers, this hiss may be noticeable from tweeters, so it's something to be aware of. Next thing is the speaker terminals on rear are a bit flimsy and seem like they could break off easily, so be gentle. Another thing is that when the amp goes into standby mode when using auto on setting, the amp itself makes a high pitch whine. It's subtle and those with less sensitive ears may not notice it but it was enough that I decided to just keep the amp on, since it switches off during movie dialogue anyway, even with sub level in receiver set at max. It barely gets warm (since only running at 8ohms) even after hours of music so I'm mostly fine leaving it on. So I'm okay with it, not annoyed enough to return and search endlessly for a chance at something marginally better but it's a bit overpriced for the build quality due to these quirks unless I just got one that was rushed through assembly.

Updated review [2023]: Still working great! I said I would come back and update to five stars if they lasted. Well they did. And here I am updating to five stars. Original review [2018]: I have had mixed experience with Monoprice quality. I was skeptical of these. But I got four of them and racked them up for use in a whole house audio system connected to a Denon HEOS SuperLink. They have all the features needed for a custom install like mine. The HEOS powers them up by a trigger and with the trigger passthrough on the amp I can also power up my fans when the amps are on. When in standby mode they power on within 1-2 seconds of getting the trigger signal. The layout on the back is logical and not crammed together making for a quick install. The rack mounting kit is good and the ability to mount two next to each other is very nice. And these things have a LOT of power. I currently have the volume set to about 3/5ths and it is just too much power for my rooms. I have to keep the variable control on the HEOS down very low. I plan to turn the amps back to about 2/5ths or 1/3rd so I have more control through the HEOS app. Since I just recently installed them I am hesitant to give them 5 stars and I don't know how the longevity will be. If they last a decent amount of time without dying I will come back and increase to 5 stars. Honestly, I have done tons of research and gone through various iterations on my DIY whole house audio system. The HEOS SuperLink combined with these amps is just spectacular. I can't imagine any combination would do better.

I understand that two of these could be combined to fill a 1u rack but one using a single one the long rack ear makes for a saggy and flimsy feel into the cabinet. Audio quality is distortion free to my ear and stays relatively cool during operation the volume leaves something to be desired but when combined with a mixer or other preamp source it becomes a non point.