AIYIMAA70 Balanced Stereo Amplifier with PFFB,TPA3255 2 Channel Class D Amp for Desktop Home Theater Bookshelf Speaker,with XLR&RCA Inputs&Trigger Input (A70 + DC48V 5A Power Adapter)ClimatePartner certified

I was skeptical about those small amps, but the tech was not standing still. Today those small amps are on the level. Not all, like Fosi Audio V3 mono was a disappointment - the volume levels are different (~3db) in each amp, so how you suppose to listen to it? But this one did great. The stock A70, for sure, made YAMAHA A-S501 run for the money. Not sure what those big names manufacturers are doing, those small inexpensive quality amps will eat the market. I am thinking now what would happen after opamps upgrade (getting second unit while on sale to experiment). Before you upgrade, know the facts: it comes with NE5532 - it was the gold standard for over 30 years in the professional audio and still produced and very affordable. Most of music produced in last 35 years was made with those opamps. At this point, I think OPA2134PA would be a step up (comes from very reputable Burr Brown lab and very affordable). Many opamps are slightly "coloring" the source thus making folks to believe some are better or not based on current audio setup and personal preferences. Ideally - you should hear no difference between the two reference opamps as those should not introduce any "coloring" to the source.The amp stays cool. I got AIYIMA 48V 10A power supply separately. The sub output is very convenient (I do not care about amp's low-pas filter, keeping it at lowest 150Hz) as I use separate sub amp with low-pass built-in (Fosi Audio TP-02 Subwoofer Amplifier, planning to upgrade toAIYIMA A70 Mono Amplifier) with passive Dayton Audio MKSX4 (very musical sub). Keeping amp A70 volume level around 11 o'clock with ELAC Debut 2.0 F6.2.Having 12V triggers makes the on/off power management a breeze.PS: OPA2134PA did change the sound a bit to more worm and bass-y, but at expense of "brilliant" highs of NE5532. Next stop are the MUSES02, but I have low expectations at this point: there are reasons of why TI NE5532 was dominating for so, so, so long.

First things first - the unit I purchased from this Amazon page did not come with a power supply. I knew this going in and I have quite a few power supplies on hand making this even more of a bargain since I did not need to pay for a power supply with this order. Aside from the differences in power supplies and their impact on sound, the A70 uses TPA3255 amplifier chip that other manufacturers are using as well, but with this iteration, Aiyima found a sweet spot between cost and performance, while exceeding the performance of past designs. The sound quality is excellent for the price. The build quality is very good. If you are adventurous, changing the 8-pin DIP opamps takes a little bit of work to install, but it is worthwhile if you want to squeeze more sound quality from the A70.I eventually settled on using a 48V 6A GanFET power supply and Oracle II opamp replacements. With this combo, I kept all the clarity of the original sound (using the opamps that came with the unit) and improved the smoothness of the sound delivery and had plenty of juice to crank tunes.The reason I was attracted to the Aiyima A70 was that it has a subwoofer output via a single RCA connection to a small powered subwoofer for a desktop setup (subwoofer in the floor). For those that has tried TPA3255 based amplifiers, you know how these chip amps struggle with the lowest of low frequency output. The sound signature at the bottom octaves is good, but having a purpose built amplified subwoofer complimenting a stereo speaker pair is the way to go to address full spectrum sound.So, if you’re looking for a compact inexpensive amplifier that can connect to a powered subwoofer for the low end, I highly recommend the A70. Buy with a power supply or use your own (watch the required voltage which is higher than other TPA3255 amps) - either way, get ready for easy setup, clear sound, and music fun.

I'm using this amplifier for a desktop audio system with Revel M105 speakers and a WiiM Ultra acting (poorly) as the preamplifier. I wanted plenty of power since the Revel's have only 86db sensitivity. I considered Hypex and Purifi DIY amplifiers that rate very highly but are overpriced for a PCB in a box. Technologically this amplifier has everything those do for much less. The majority of the design and the TDA3255 chips were made by Texas Instruments, including PFFB. As for the implementation, I have to hope Aiyima followed TI's design guidelines and used decent components so this amp has some longevity. We all know Amazon reviews are like JD Power car reviews, only good for initial impressions and not long-term reliability.I have no problem with the separate power brick since it can only improve the audio signal by being outside the case with its noise and heat. You are also somewhat protected if the PS dies since you can get another without throwing the good part of the amp away. A third benefit is you can buy a power supply with more wattage to increase the output of the amplifier if you need it.Please note that the specs for this amp are like all from the far east. Exaggerated and unreachable. Some of the blame falls on TI for listing a ludicrous power figure @ 10% THD in their own data sheet. Nevertheless you can still get an honest 150-200 watts per channel with inaudible noise and distortion that rate far below .01%. With Post Filter Feedback (PFFB) the load dependency from the speakers is eliminated which means the frequency response is flat from roughly 20 to 20K Hz. Brilliant.So far this device has done exactly what I wanted. A class D amplifier based on the state of the art design that eliminates all the shortcomings of old class D. I'm not going to tell you it sounds "sweet and melodious with musical but not bright highs" because that doesn't mean anything to anyone. It sounds like _nothing_ which is the best compliment an amplifier can receive.