{"product_id":"kteli-st21-2-1-digital-power-amplifier-board-compact-2x100w-200w","title":"KTELI ST21 2.1 Digital Power Amplifier Board - Compact 2x100W+200W","description":"\u003cp\u003eIn this review the KTELI ST21 is judged as a compact 2.1 channel amplifier board that suits DIY audio builders and compact home theater upgrades; the single biggest reason to buy is its high output-to-size ratio, delivering up to 105W per stereo channel and about 208W to a subwoofer from a 24-30V supply while offering Bluetooth 5.1 connectivity. The board is practical for people who want a powered compact solution with multiple inputs, and the review focuses on real-world compatibility, power needs, and how the board handles different speaker impedances.\u003c\/p\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e2.1 Channel Output:\u003c\/strong\u003e Provides left and right channels plus a dedicated subwoofer channel so users can build a compact two-speaker plus subwoofer system with clear separation.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh Power Capability:\u003c\/strong\u003e Delivers up to roughly 105W per stereo channel and up to about 208W to the subwoofer at higher voltages, making it suitable for medium-power home audio setups.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eWide Voltage Range:\u003c\/strong\u003e Operates from 12-30VDC with a recommended 24-28V, letting installers choose a DC supply that balances available current and desired output.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eBluetooth 5.1:\u003c\/strong\u003e Built-in Bluetooth with about 15m transmission distance for easy wireless streaming from phones or tablets without extra dongles.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMultiple Inputs:\u003c\/strong\u003e Supports Bluetooth, AUX, U disk and sound card inputs, which allows connection to legacy sources as well as digital media on a thumb drive.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTI TPA3221 Amplifier Chips:\u003c\/strong\u003e Uses proven TI power amp ICs for the left and right channels to provide efficient amplification and protection features suited to powered speaker projects.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWho It's For\u003c\/h2\u003e\n\u003cp\u003eThe ST21 is aimed at hobbyists, builders of compact home theater or desktop speaker systems, and installers who want a single board to drive stereo speakers plus a subwoofer with both wired and wireless inputs. It is especially useful where space is limited but higher subwoofer output is desired.\u003c\/p\u003e\n\u003cp\u003eIt is not the best choice for users who need a built-in enclosure, plug-and-play consumer AV receiver features, or those who cannot provide a suitable 24-28V DC supply rated for 10A or more. Also, buyers who require digital room correction, HDMI switching, or network streaming should look elsewhere.\u003c\/p\u003e\n\u003ch2\u003ePros \u0026amp; Cons\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePros\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eGenerous power output for stereo and sub channels relative to the module's compact footprint.\u003c\/li\u003e\n\u003cli\u003eFlexible input options and Bluetooth 5.1 make source hookup straightforward for most setups.\u003c\/li\u003e\n\u003cli\u003eWide operating voltage gives installers options to tune power versus heat and efficiency.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCons\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eRequires an external DC supply (recommended 24-28V, 10A) and basic wiring skills to install safely.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003ctd\u003eProduct type\u003c\/td\u003e\n\u003ctd\u003e2.1 channel Bluetooth amplifier board\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChannels\u003c\/td\u003e\n\u003ctd\u003eLeft, Right, Subwoofer (2.1)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRecommended supply\u003c\/td\u003e\n\u003ctd\u003e24-28VDC, 10A or greater\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating voltage range\u003c\/td\u003e\n\u003ctd\u003e12-30VDC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower output (approx)\u003c\/td\u003e\n\u003ctd\u003eLeft\/Right up to 105W@30V 4ohm; Sub up to 208W@30V 2ohm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBluetooth\u003c\/td\u003e\n\u003ctd\u003eBluetooth 5.1, ~15m range\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAmplifier chips\u003c\/td\u003e\n\u003ctd\u003eTI TPA3221 (stereo channels)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch2\u003eOur Verdict\u003c\/h2\u003e\n\u003cp\u003eThe KTELI ST21 board is a solid value for DIYers and compact audio system builders who need robust subwoofer output and flexible inputs without a bulky receiver. It offers impressive power for its size when paired with a proper 24-28VDC supply, and the inclusion of Bluetooth 5.1 and multiple inputs makes it a practical core for a small home theater or powered speaker project.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eWhat power supply do I need?\u003c\/strong\u003e\u003cbr\u003eYou should use a DC supply within 24-28V and capable of supplying at least 10A for reliable performance and near-maximum output.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eWhat speaker impedances are supported?\u003c\/strong\u003e\u003cbr\u003eThe left and right channels support 3-8 ohm speakers up to 100W each; the subwoofer supports 2-8 ohm drivers up to 200W.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes it have wireless streaming?\u003c\/strong\u003e\u003cbr\u003eYes, it includes Bluetooth 5.1 with a typical transmission distance of around 15m for wireless audio streaming.\u003c\/p\u003e","brand":"KTELI","offers":[{"title":"Default Title","offer_id":46765958496475,"sku":"B0D1G4XF3K","price":39.79,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0724\/1043\/1707\/files\/61hb0zFo5OL._SL1001.jpg?v=1747854680","url":"https:\/\/gearmusthave.com\/products\/kteli-st21-2-1-digital-power-amplifier-board-compact-2x100w-200w","provider":"GearMustHave","version":"1.0","type":"link"}