ZK-TB21

I was using a vintage Pioneer 25W/ch receiver for the sound system in the workshop. I also have an old JBL powered subwoofer that had the amp go out, so I decided to order this little amp to see if I could power the old sub with it and at the same time replace the old Pioneer receiver for a little more volume, in addition to the sub added.The final setup: Two existing ceiling speakers, 8 Ohms each, paralleled with two Klipsch bookshelf speakers, 8 Ohms each , for a net 4 Ohms per channel; re-purposed JBL sub that has two 5 Ohm speakers in parallel, so 2.5 Ohms total. Amp is powered by a 24V/100W LED driver.The result: awesome! The bass could be better, but considering that the subs are only 6” diameter, not bad, certainly much better than without the sub. The Klipsch bookshelf speakers add a lot to the midrange and highs, complementing the ceiling speakers.As for the power supply, I first hooked it up with a 24V 60W power supply, and it worked fine, although the subwoofer started to clip at a fairly low volume. The power supply never got warm however. I tried a 24V/100W power supply anyway, and the bass was vastly improved. This tells me that the 60W was not able to supply the current peaks, so the 100W is staying. So, spend a little more and go for the bigger power supply to get more distortion-free bass.What I like about this amp: BT works flawlessly, connecting each time without fail. The range could be better, but understandable since the built in antenna is just a small PCB trace. There is a connector for an external BT antenna if desired. I like the audio controls: Bass frequency cutoff and volume, treble/bass/volume for the stereo channels. The amp is very power efficient, and has more power available than what I need. With a 24V power supply, driving 4 Ohms per channel + 2.5 Ohms subwoofer, it barely gets warm after several hours.My only complaint: The speaker terminals are tiny, so stacking wires greater than 2x 18ga can be difficult.Bottom line: highly recommended.

I have not taken any pics yet so I will add them when it’s all ready, but I will say that I’m blown away with this little beast. I have been a car audio competitor for around 20 years now and have 2 world titles. I purchased the zx-100zl first to test the waters and still have it as the outside patio stereo and theater system. So I did not hesitate when my finger clicked on the order button for this 3 channel with separate sub unit with the treble, bass, sub volume, cross over control,and main volume knobs, which are very smooth and adjust flawlessly with no static or interference noises rolling out at all. The built in crossover is a little disappointing and is more like a cut frequency and wattage knob. I have hooked up a hand full of subs and pro woofers to see if box design would help or sub specs might be a factor but they all have the same sweet spot and going below that just kills the output, but the sweet spot is right at the spot that it needs to be anyway with every genre I went through, for me anyway. If possible try to get the unit as close to 24v as you can or at least 20v if you want to be able to utilize the units full potential. I am using a small digital voltage regulator or buck unit inline with the 19v laptop charger. That way I can just turn the adjustment knob up or down to go to 24v or down to 9v if I want to for some reason put some small 5w speakers on it, I won’t.. the sound clarity is flawless through the whole scale. Tweet response is on point. Mids and vocals are clear and powerful. If you keep the sub crossover above half way which seems to be around 100hz, you won’t loose any significant power. Over 100hz out of sub starts distorting the lowend vocals anyway so it works fine. I ended up putting a passive sub crossover inline out of the unit anyways just cause I already have some and it seems to really open up the wattage flow that the units crossover was smothering. At the moment I have 4 Yamaha 3 way 100w bookshelf speakers on the 2x50w full range channels and 2 6.5” subwoofers in a down fire custom built ported sub box tuned to 45hz on the 100w sub channel. I have it bluetoothed to my theater in my home office, aka work space, gaming system and second theater room. I can go from a virtual power point webinar to streaming John wick 3 on the 4K, to madden 21 on the xbox one or asphalt 9 on the gaming pc, and this little marvel is crisp, clean, clear, and will have the neighbors yelling at me with no problems. I highly recommend this bad boy even if you don’t need it. You will find a use for it. You will make use for it anyway. It’s that good.. also I would like to give 5 stars to the damgoo team for all the quick responses and customer first mentality that they seem to have perfected and have done nothing less then been amazing and don’t make you feel like just a customer but a personal friend from the first interaction. If everyone conducted business the way they do, the world would be a little nicer to itself.. sorry for the long winded review but how else could I have explained it. Awesome...