Douk AudioA5 2 Channel TPA3255 Stereo Amp, 300 Watts x2 Mini Hi-Fi Audio Power Amplifier Class D for Home Theater System, Passive Bookshelf Tower Speakers with High-Pass Filter + 32V Power Supply

I found the sound of the Douk Audio A5 stereo amplifier to be natural sounding and dynamic. Although not noted in the provided product documentation, my understanding is that the Douk Audio A5 amplifier features post filter feedback (PFFB) for improved sound. PFFB can result in an amplifier achieving overall flatter frequency response that is less affected by speaker impedance changes across the audio spectrum. The right knob is the volume control. This control doubles as the power switch. There is no power indicator LED on the front panel of the A5.There are 3 multi-segment LEDs inside the A5 amplifier. These LEDs can be configured via dip switches located inside the unit to provide Red, Green or Blue illumination (or any combination of these three colors) to the inside of the A5 amplifier. There is a clear insert in the top cover of the A5 that can be easily removed to access the dip switches and the A5's other circuitry. There are two swappable op amps inside the A5 amplifier that can be changed if desired. On the rear of the A5 there is a 3.5mm output connection labeled Aux Out. I confirmed that the A5's Aux Out level is variable, full frequency. (Douk Audio could have labeled the 3.5mm connection as Pre Out or Sub Out.) The Aux Out level is controlled by the volume knob setting on the A5.The left knob on the front of the A5 lets you activate and adjust the high-pass filter. When switched on, the high-pass filter can be set anywhere between 30Hz and 200Hz. (Note that there are no conventional bass or treble tone controls on the A5.) The high-pass filter only affects the speaker level outputs and has no effect on the Aux Out's audio. Even without a subwoofer the A5's high-pass filter can be useful if you desire to roll off the lowest bass frequencies that are sent to the speakers.The A5 comes with a Douk/Nob Sound branded power supply rated at 32 volts and 5 amps. The included A5 documentation states the A5 is capable of 300 Watts x 2 @ 4 ohms. With the stock 32V/5A power supply I estimate the A5 is able to deliver ~50 Watts per channel output @ 8 ohms. You can substitute a 48 volt, 10 amp power supply so that the A5 would be able to deliver its maximum power. The case of the A5 amplifier, when used with the stock 32 volt power supply, runs about the same temperature as the Aiyima A07 Max with that amplifier's stock 36V/6A power supply. The A5's case temperature reading was ~82F, in standby and 90F when in use. In comparison, the Fosi Audio TB10D amplifier's case measured 72F, in standby and in use. [Update: I measured the standby power consumption of the A5 amplifier. Plugged in, not switched on, the power consumption measured 0.3 Watt. Powered on, no input signal, 4.7 Watts.]

I purchased and received a Douk Audio A5 from Amazon a few weeks ago. It is a nice little amp. I purchased it for speaker testing purposes (I got tired of lugging around my bigger class AB amps) and to run my little PA speakers every now and then (ditto). I've been listening to it for some time now and it seems like a solid little amp. Pretty tight bass too. And I did have my doubts about it, but that variable high-pass filter has turned out to be very useful. At no time did I feel the need to use a more powerful PSU with the A5.Additional plus - you can use dual banana plugs with the A5. You just need to wire them up differently. Use one across the positive terminals, and the other across the negative terminals. Of course, that could have been avoided if the output terminals were arranged (+ - / + - ) rather than (+ + / - - ), so I guess that's peeve #4, LOL.I purchased and received an Douk Audio A5 from Amazon a few days. Nice little amp. Purchased it for testing purposes and to run my little PA speakers every now and then. I've been listening to it for some time now and it seems like a solid little amp. Pretty tight bass too. And although I did have some initial doubts about it, the variable high-pass filter has turned out to be very useful.Note: My test speakers are a pair of DIY ones I put together a few years ago. They're rather insensitive (designed for nearfield use), and at no time did I feel the need to use a more powerful PSU with the A5. The Fb for the speakers is around 50 Hz, so I set the HP filter below that, basically by turning it up until the bass started to noticeably reduce in volume, then turning it back down slightly.My only peeves so far are: (1) 32V PSU is the only option offered for it off of Amazon, (2) The clear acrylic top cover can't be fastened into place (which means I'll have to rig up something - until that happens I've left the peel-off sticker in place), (3) the volume control knob is basically useless until rotated past the 9 o'clock position.Additional plus - you can use dual banana plugs with the A5! You just need to wire them up differently. Use one across the positive terminals, and the other across the negative terminals. Of course, that could have been avoided if the output terminals were arranged (+ - / + - ) rather than (+ + / - - ), so I guess that's peeve #4, LOL.Now, is Douk Audio going to produce a companion subwoofer amplifier to match the A5? Basically, the A5 with an adjustable low-pass filter instead? Or, even better, with adjustable low-pass and high-pass filters :). I'd immediately place something like very high on my purchase list.