ZK-TB21 2.1 Channel Bluetooth Amplifier Board for DIY Speakers, TPA3116 Chip, 50W × 2 + 100W, BT and AUX Input, DC 12–24V, Mini Amp wih Bass & Treble Control

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...

I have been looking at these inexpensive little amps for a few years and never really had a use for one, as I have a pile of older amps around the house for my systems. I have been upgrading my home office and decided it was time to bring some solid music playing into the office, as I do my best work with LOUD music ;-). had a pair of Polk bookshelf speakers that had been sitting in their original box for a few years from when I picked them up on sale from Frys. wanted a small amp to drive these off my PC, Alexa, and TV, and I liked the idea of how small this amp was and could mount it under my desk. had concerns about such a small amp pushing 8-ohm speakers as most folks were using it with 4-ohm set-ups. If I got I could return it it and did not like the sound/power, I could e you do need to do some assembly, and I recommend some felt feet if you plan to put this on a surface. Assembly was easy, and I quickly wired up the Polks. At first, they sounded like crap, but then I started to play with the tone and slowly dialed them in. The Sound got better as time went on. Like most amps/speakers, I find they need a little time to warm up, and the sound gets richer. With just the polls, I got pretty good sound and loud enough to annoy my wife. But, the amp would distort at the highest output. The Polks do not have a very low range, so the base was lacking. This is where I made a mistake when choosing this amp. It has a powered output for the sub amp, so you need a passive sub, and most home subs on the market today are powered. I did not want to spend a fortune on a sub, so I looked into making one and came up with a cost of about $50-80, depending on what drivers I chose. Then it occurred to me that a lot of the 'home media' speaker set-ups come with a passive sub, so off I went to eBay. I bought a refurbed SONY passive sub for $30 delivered on eBay. I got it and hooked it up, and immediately, the package was complete. With the sub hooked up, this amp has plenty of power to drive all 3 speakers and get very loud without any distortion. Still dialing it in some more, but it just gets better. If you want a cheap little set-up that you don't need 'high-end' sound, this is the amp for you. I think I will pick up a few more to drive my outdoor speakers this summer because I can hide the amp just about anywhere and very little heat. I did have to buy a power cord for a few bucks, but you can use an old laptop cord if you have one.

Amazing for its size! Sound quality is best when treble and bass filters are all the way up at maximum. These are moderate filters having little fine bandwidth effect. But the Bluetooth connectivity is super great and for my rv, replacing the shaken-to-death Jensen ($$$!!), this amp produces plenty of power! And the package is easily adaptable to most any situation. A good product for the money if accurate reproduction of your favorite recordings is not required.

I have been using this quite regularly and I am impressed with the sound coming out of this. I am using a 24V 5AMP converter. Awesome little Bluetooth amp!

Works perfectly for a DIY home surround sound system.

Sound quality is very good, of course your source will also depend on how good the output is. Running it with a 19.5v 7.1A laptop power adapter to 2 40 watt bookshelf speakers, it gets very loud, I can't turn it up past halfway or it's too much for these bookshelf speakers to handle, they have a 4" speaker and it vibrates my entire computer desk if turned up loud enough. Had these hooked up to a cheap class AB amp and it's worlds of difference between it and this amp. Cons: It would be nice if there was a way to turn off the Bluetooth function and the blinking blue light. There's a small area at very low volume where the output jumps noticeably instead of being a smooth progression, might just be a wonky potentiometer "volume control knob" and really isn't much of a bother since it's at extremely low volume level.

EDIT: I cannot use this amp sometimes because of the unsecured Bluetooth. I live on a 1/4 acre lot in a 2200 sq ft house, but due to the unsecured Bluetooth and overly strong signal strength, my neighbors from all sides are able to accidentally connect to this device. There's no way to turn it off and the amp defaults to Bluetooth, so if anyone in the surrounding area accidentally selects my amp on their device, their audio plays through my amp and I'm not able to lock them out - if the amp is turned on I have no option but to listen to their audio. I currently have the amp partially wrapped in aluminum foil, which helps, but this is still happening due to the unsecured BT combined with overly strong (FCC compliant?) signal. This little amp has impressive output but has some serious design flaws: 1. Bluetooth: The Bluetooth module on this amp is unsecured which means anyone with a device within range can connect to it, even accidentally. It also prioritizes Bluetooth over the input jack and there's no way to turn Bluetooth off, which means that the amp becomes unusable if someone else nearby connects to your Bluetooth. I have had serious problems with others (neighbors, visitors, and family in my own house) accidentally connecting to this amp because the module is always on and lets any device in range connect. IF ANYONE ELSE CONNECTS TO YOUR AMP, YOU ARE EFFECTIVELY LOCKED OUT OF IT!!!! Right now this POS is wrapped in aluminum foil to try to prevent signals from reaching the antenna because I was locked out of my own amp!!! 2. Crossover: The built-in crossover (sub frequency adjustment) is beyond worthless and kills bass output. It does not adjust crossover frequency, it is set around 200Hz and then roll the slope curve above or below 200Hz. What happens in practice is that, when adjusted, below the middle setting it kills low end output because those freqs are effectively chopped out, when turned up above the middle setting it boosts frequencies in the 200-300hz range creating weirdly booming mid-bass. Totally worthless. Best bet is to set it on the middle setting and then use external crossovers to do it right. This amp would be so much better without the "extra" features which were not properly designed. The amp itself in incredible, lots of power and amazing for it's tiny size. I'm running two Dayton MK442s and a 10" ported sub and it has no problems pushing those drivers plenty loud. But the Bluetooth renders my amp inoperable and the frequency adjustment is garbage.

Super potente, me levantó facilísimo dos bafles antiguos Fisher con un bajo, una bocina y un tweter cada bafle. Le coloque una fuente de laptop de 19V/3Amp y no se calienta. Recomendado al 100%

Ho comprato questa scheda amplificatore Bluetooth a 2.1 canali per collegarlo in parallelo all'impianto acustico che avevo in garage, collegato ad un autoradio Apline 50W X 4... però mi serviva anche un ricevitore bluetooth per collegare il mio smatphone… il collegamento è stato fatto in parallelo con l’autoradio inserendo un commutatore per l’alimentazione come in foto, in modo da poter accendere solo l’autoradio oppure solo la scheda amplificatore Bluetooth, come alimentatore ho usato quello che avevo per l’autoradio (trasformatore stabilizzatore 13,6v 5A) il tutto funziona molto bene, l’impianto è formato da un sub woofer da 50W + un woofer da 50W + due casse a tre vie da 100W +100W, alzando il volume al 50% il suono è molto forte e con il giusto settaggio si sente moto bene, lo uso da circa due mesi e non ha dato nessun problema. Qualità/prezzo eccellente, Lo consiglio. N.B. per avere una buona resa bisogna collegarlo ad un trasformatore con una buona potenza, altrimenti quando si alza il volume non rende bene perchè ha bisogno di più potenza,

For the price of it this produces great sound quality and has lots of power

Utilisé avec des enceintes dans l'atelier. Fait le job. Bon rapport qualité/prix

Tengo el estereo que venía con estas bocinas comprados por ahí de 2002 nuevo, después de años seguía funcionando pero a medias , los botones ya no respondían muy bien y lo peor de todo a bajo volumen había intermitencia en al audio. Con este amplificador han vuelto a la vida mis bocinas y su subwoofer, se escuchan muy bien, le adapte un cargador de laptop de 19v 5A y funciona muy bien.