I've owned one of these amps now for about six months. All the complaints I've read in the reviews have come from people who obviously can't be bothered to read, pay attention, or think things through. I'm specifically referring to Auto Input Switching/Power, lack of features, and output power.
First, this is NOT an integrated amp. Nor is it designed to be used primarily as a standalone system. It is intended to be used as a node on a distributed music system. The feature set for this unit has this use in mind.
It can function as a standalone unit but if you are going to use it as such you need to use it with a pre-amp or with an input source that provides adequate line in, input selection and the tone/equalization control you want.
Second, the auto input switching. The manual isn't clear on this and the feature can't be switched off, which is why I docked it a star. But some reading and thought will provide the solution. The auto input feature is only on input 1. If you run your primary input to input 2 you will have no problem with auto switching cutting off your music during quiet passages or after the track has started. If you need to use multiple sources without the auto switch cutting the input then you need to use external input switching (see pre-amp above) and make sure the switch/pre-amp is fed to input 2 on the amp.
Auto-power on issues: This feature can be turned on or off by way of a selector switch on the rear panel of the amp. Default is on. This is in the manual.
"It doesn't have a sub out": No, but it does have a line out/pass-through for input 2 which can be used for a sub out.
"It isn't loud enough": One of two things is happening here; 1. The line in isn't sufficient to properly drive the amp. 2. The speakers aren't efficient enough. If you are running speakers with less than 90db sensitivity you won't get decent performance from this or any other "low power" amp. I'm using Athena AS-B1.2's and I'm getting more than adequate volume and bass response. I recommend these (under $100 if you shop around) or the Athena AS-B2.2. Klipsch, Infinity, JBL, and Yamaha all make some nice bookshelf units with 90db sensitivity or better that would work nicely with this unit. Just because this is an inexpensive amp doesn't mean you can get away with cheap speakers.
"There isn't enough bass": 1. Make sure the source is providing enough bass input. If the source doesn't have a tone control for bass you may need to use a pre-amp. 2. Use better speakers. When I first got my amp the speakers I had ordered for it were delayed, so I used some old early 80's bookshelf speakers to test the amp out.
Those speakers had no bass at all, or treble, or much midrange. Basically it sounded like an AM pocket radio. When the Athenas came in and were properly broken in the sound improved greatly. It also helps to have the speakers placed properly. If your speakers are rear vented they don't need to be in an enclosed space or pushed up against a wall (I see this all the time, even on store displays).
My experiences with this Amp: I ordered this amp with a pair of Athena AS-B1.2 bookshelf speakers for use in my home office. Inputs are from my PC (by USB DAC) and an iPod dock. Both inputs run through an audio switch to input 2 on the amp. The files played through it are a mix of OGG, FLAC, AAC, ALAC, WAV, and MP3. Mostly FLAC.
I was impressed by the fit and finish of the unit out of the box. I've seen many allegedly high end products that don't have this level of finish (Cameras, turntables, TV, PC Cases, Cars, etc.). The weight is substantial. As near as I can tell by looking through the vent slots the transformer takes up at least half the case. The power lines in my house aren't very clean and I have hum issues with most A/V equipment I own, but I have yet to hear any hum (in normal conditions) from this amp when turned all the way up, even when it's been plugged into outlets that give other equipment fits. The only way to get hum is to touch an input with a finger. In normal use the background is dead silent. Good power supply.
The design is minimalist and clean. The only panel controls are power, speakers, volume and balance. It is low profile and unobtrusive and gives off very little heat, even when left on (with the volume turned down). Mine doubles as a monitor stand, LCDs only.
There are two inputs but they are auto switched. The first input is the auto switch input, as stated above. This means that if an input is detected it will switch to input 1 over input 2. It is fairly sensitive and will switch back and forth during pauses or quieter passages in the music. If you listen to a lot of Jazz, classical, or chamber music with pauses and quiet bits you will definitely want to use input 2 to prevent it from dropping out during those passages.
There is an autopower feature as well. If left on it will cause the same problems with the amp cutting out during quiet passages as the autoinput switching. However it can be disabled by a selector switch on the back of the unit. This is clearly explained in the manual. The intent is to allow the unit to be powered on remotely when used with a distributed music system. If you want a standalone system disable this feature and turn it on and off manually.
The sound is deep and rich with excellent separation, depth, and imaging. There's plenty of bass for most of what I listen too (Jazz, folk, and classic rock), and outstanding midrange. Treble does seem to roll off a bit, but that may be the speakers. Volume is more than enough to shake the walls and floor of my office and the music can be heard clearly throughout the second floor of the house. Personally I think it's more than loud enough to use as a primary system if you have a smallish living room (but with larger speakers). I haven't heard any distortion at loud volumes, but excessive line in might change that. More importantly to me the sound doesn't get muddy at low volume levels. It remains clear and detailed. I have no problem listening to most of my collection for hours on end with this amp while I work, or kicking back on the office sofa with some whiskey.
Most of my music files on the PC are lossless, but I do have a few dogs among the MP3 and WAV files. It's no great feat for an amp to sound good with a lossless file so I ran a few of the nastier files through it to see how it did. For the most part it took the edginess off most of the rougher files and made them almost pleasant to listen to. There are a few bad tracks that are best left to regular PC speakers, and a few FLAC files ripped from CD where bad mastering shows up more clearly now. Win some, loose some.
Nitpicks: My amp pops when turned on and off, which has the potential to damage speakers. It's not loud, but I turn the volume down before I hit the switch. I would prefer a manual input switch. Price has changed by as much as $30 on Amazon over a relatively short time.
Before buying this I listened to a friend's office setup with a Super T-Amp and a pair of Infinity Bookshelf speakers. To my ears the Amp100 sounds just as nice at lower volumes plus it can pack more of a punch when called for. It's not as compact as the Super-T or as stylish, but it fills my needs.