Fosi Audio MC101 is a compact Bluetooth stereo integrated amplifier for passive speakers, styled with an illuminated analog VU meter.Bluetooth 5.3, RCA input, pre-out, tone controls and up to 100W per channel maximum output combine modern connectivity with tactile vintage-inspired control.Why it stands outIlluminated analog VU meterThe moving pointer provides a distinctive visual indication that follows the audio signal.Bluetooth and RCA inputsSwitch between Bluetooth 5.3 wireless playback and a conventional analog source.Passive-speaker amplificationDual TPA3116 amplifiers provide up to 100W × 2 maximum at 4Ω.Pre-out system expansionConnect compatible powered equipment or an additional amplifier from the line-level pre-output.Best for Desktop and bookshelf passive speakers Simple Bluetooth stereo systems Users who value physical tone controls Systems needing a pre-output for expansion Not ideal for HDMI ARC, optical or USB sources Headphone listening Turntables without a phono preamplifier EMiUZEK Buying Notes MC101 powers passive speakers; the pre-out is line level and should not be connected to passive speakers. The 100W × 2 figure is a maximum specification at 4Ω and depends on power supply and load. A turntable needs a built-in or separate phono preamplifier before the RCA input. Frequently asked questionsCan MC101 power passive speakers?Yes, through its rear speaker binding posts.Does it have a subwoofer output?It has a full-range pre-out; a powered subwoofer must provide a compatible input and crossover.Does it include a phono stage?No.Can it connect to a TV?Only when the TV provides compatible analog output; there is no optical or HDMI input.What Bluetooth codecs are supported?SBC and AAC.Can it drive headphones?No headphone output is provided.HOW TO CONNECTBluetooth stereoSource icon: phoneSource: Phone / tabletConnection: Bluetooth 5.3Output connection: Speaker terminalsTarget icon: speakersOutput: Passive speakersWired stereoSource icon: streamerSource: Streamer / DAC / TV analog outputConnection: RCA line inputOutput connection: Speaker terminalsTarget icon: speakersOutput: Passive speakersExpanded systemSource icon: streamerSource: Bluetooth or RCA sourceConnection: Bluetooth or RCAOutput connection: Pre-outTarget icon: speakersOutput: Powered subwoofer, powered speakers or downstream amplifierTechnical SpecificationsConnections Feature Specification Inputs Bluetooth 5.3; RCA Outputs Speaker binding posts; pre-out Bluetooth codecs SBC; AAC Bluetooth range ≥10m Amplification Feature Specification Channels 2 Amplifier chipset 2 × TI TPA3116 Maximum output 100W × 2 @ 4Ω SNR ≥100dB THD ≤0.03% Frequency response 20Hz–20kHz (±1.8dB) DC input 12–24V Supplied adapter 24V / 4.5A Additional Product ContentComparison: Which Fosi Audio model is right for you? Model MC101 BT20A BT20A Pro Amplifier Dual TPA3116 Dual TPA3116D2 TPA3255 Maximum stated output 100W × 2 @ 4Ω 100W × 2 300W × 2 @ 4Ω Pre-out Yes No 3.5mm variable pre-out Signature feature Illuminated VU meter Simple compact stereo Higher output and op-amp rolling Best use Vintage-style Bluetooth stereo Entry compact system Expandable higher-output system

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Fosi Audio HT4S is a compact 4.1/5.0-channel integrated amplifier for multi-speaker, outdoor-audio and simulator systems.Bluetooth, optical and 3.5mm inputs, five amplified channels and a switchable sub/center channel create a flexible multi-speaker system without a full-size AV receiver.Why it stands outSwitchable 4.1 or 5.0 operationConfigure four main speakers plus a subwoofer channel, or use five full-range speaker channels.Built-in multi-channel powerProvides four 30W channels plus a 60W sub channel in 4.1 mode, or five 30W channels in 5.0 mode.Digital and wireless inputsConnect optical PCM, 3.5mm analog or Bluetooth sources.Remote and front-panel controlAdjust source, volume, tone and operation without a separate controller.Best for Outdoor and patio multi-speaker systems Sim-racing bass-shaker installations Compact 4.1 or 5.0 speaker systems TV systems with optical PCM output Not ideal for Dolby or DTS surround decoding Systems requiring HDMI ARC Speakers below the specified 4Ω minimum EMiUZEK Buying Notes HT4S is a multi-channel amplifier, not an HDMI adapter or surround-sound decoder. Set the source to PCM stereo when using optical; encoded Dolby/DTS signals are not supported. The SUB/CEN output changes function with the selected mode, so confirm the switch setting before connecting speakers. Frequently asked questionsDoes HT4S have HDMI?No. Inputs are Bluetooth, optical and 3.5mm AUX.Does it decode Dolby or DTS?No. Use a compatible PCM signal.Can it run five passive speakers?Yes, in 5.0 mode with compatible 4–8Ω speakers.Can it power a passive subwoofer?Yes, in 4.1 mode through the dedicated amplified SUB/CEN channel.Does it have a line output?Yes, a 3.5mm pre-out is provided.Can it be used outdoors?It can power outdoor speakers, but the amplifier itself should remain protected indoors.HOW TO CONNECTOptical TV systemSource icon: tvSource: TV / projectorConnection: Optical PCMOutput connection: Speaker terminalsTarget icon: speakersOutput: Four or five passive speakersOutdoor multi-speaker systemSource icon: phoneSource: Phone / streamerConnection: Bluetooth or AUXOutput connection: Speaker terminalsTarget icon: speakersOutput: Outdoor passive speakersSim-racing systemSource icon: computerSource: PC / simulator audioConnection: Optical, AUX or BluetoothOutput connection: Speaker and SUB/CEN outputsTarget icon: speakersOutput: Speakers and compatible bass shaker / passive subwooferTechnical SpecificationsConnections Feature Specification Inputs Bluetooth; optical; 3.5mm AUX Outputs Five speaker channels; 3.5mm pre-out Speaker impedance 4–8Ω Amplification and physical Feature Specification 4.1 rated output 30W × 4 + 60W × 1 @ 4Ω 5.0 rated output 30W × 5 Maximum output 50W × 5 @ 4Ω SNR ≥88dB THD ≤0.03% AC input 110–240V Dimensions 6.1 × 7.2 × 2 in Additional Product ContentComparison: Which Fosi Audio model is right for you? Model HT4S BT30D BT30D Pro System type 4.1 / 5.0 multi-speaker 2.1 stereo Higher-output 2.1 stereo Digital input Optical None None Amplified outputs Up to five channels Stereo + passive subwoofer Stereo + passive subwoofer Maximum stated output 50W × 5 @ 4Ω 50W × 2 + 100W 165W × 2 + 350W @ 4Ω Best use Outdoor, sim racing, multi-speaker Compact moderate-output 2.1 Higher-output 2.1

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Fosi Audio BT30D Pro is a TPA3255-based 2.1-channel Bluetooth integrated amplifier for passive stereo speakers and passive or powered subwoofers.High-output Class-D amplification, separate bass controls and flexible subwoofer connections make it a compact control center for a powerful 2.1 system. Why it stands outHigh-output 2.1 amplificationDedicated stereo and subwoofer channels provide up to 165 W × 2 plus 350 W maximum at 4 Ω.Flexible subwoofer supportConnect a passive subwoofer from the amplified output or powered equipment from the 3.5 mm full-range line output.Independent system tuningMaster volume, bass, treble, subwoofer volume and subwoofer frequency controls support practical room integration.Bluetooth and RCA inputsWorks with wireless mobile sources or conventional analog line-level equipment. Best for Higher-output compact 2.1 systems Passive bookshelf or floor-standing speakers Passive or powered subwoofer integration Desktop, living-room and small TV systems with analog audio Not ideal for Systems requiring HDMI ARC, optical or USB inputs Users needing a headphone output Turntables without a phono preamplifier EMiUZEK Buying Notes The advertised 165 W × 2 + 350 W figures are maximum ratings at 4 Ω and depend on the power supply and load. The 3.5 mm output is full-range; powered subwoofers should use their own crossover where required. Bluetooth has priority over RCA, so disconnect Bluetooth to return to the wired input. Frequently asked questionsCan it power passive speakers and a passive subwoofer?Yes. It provides amplified outputs for both.Can it connect to a powered subwoofer?Yes, using the 3.5 mm full-range output and the powered subwoofer's compatible input.Can it operate as a 2.0 amplifier?Yes. A subwoofer is optional.Does it support aptX?No. The official instructions state that aptX, aptX HD and aptX Low Latency are not supported.Can it connect directly to a turntable?Only if the turntable provides line-level output; otherwise add a phono preamplifier.Can it connect to a TV?Yes when the TV has compatible analog output. It does not have HDMI ARC or optical input. HOW TO CONNECTHigh-output passive 2.1 systemSource icon: streamerSource: Streamer / DAC / phoneConnection: RCA or BluetoothOutput connection: Stereo speaker terminals + passive subwoofer terminalsTarget icon: speakersOutput: Passive speakers + passive subwooferPowered subwoofer systemSource icon: TVSource: TV analog output / DACConnection: RCAOutput connection: Stereo speaker terminals + 3.5 mm full-range outputTarget icon: speakersOutput: Passive speakers + powered subwoofer Passive 2.0 stereo systemSource icon: streamerSource: Streamer / DAC / phoneConnection: RCA or BluetoothOutput connection: Stereo speaker terminalsTarget icon: speakersOutput: Two passive speakersNote: A subwoofer is optional; leave the subwoofer outputs unused for a 2.0 system.Technical SpecificationsInputs Feature Specification Bluetooth 5.0 Included RCA line input Included Outputs Feature Specification Stereo passive-speaker output Included Passive-subwoofer speaker output Included 3.5 mm full-range line output Included Amplification Feature Specification Amplifier Chip TI TPA3255 Maximum Output 165 W × 2 + 350 W at 4 Ω Speaker Impedance 2–8 Ω Frequency Response 20 Hz–20 kHz (±1 dB) THD ≤0.04% SNR ≥108 dB Input Sensitivity 700 mV Passive Subwoofer Frequency Adjustment up to 300 Hz Connectivity and power Feature Specification Bluetooth Range up to 50 ft without obstacles DC Input Range 12–36 V Power Adapter dependent on selected variant Additional Product ContentComparison: BT30D or BT30D Pro? Feature BT30D BT30D Pro Amplifier architecture 2 × TPA3116D2 TPA3255 Maximum output 50 W × 2 + 100 W 165 W × 2 + 350 W at 4 Ω DC input range Supplied 24 V / 4.5 A 12–36 V Best use Compact moderate-output 2.1 Higher-output 2.1 systems

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Fosi Audio BT20A is a compact two-channel Class-D integrated amplifier for passive speakers, with Bluetooth and RCA inputs.It combines straightforward wireless playback, bass and treble adjustment, and up to 100 W per channel maximum output in a small desktop-friendly chassis. Why it stands outCompact passive-speaker amplifierProvides stereo speaker amplification without the size and complexity of a full-size receiver.Bluetooth and wired playbackSwitch between Bluetooth 5.0 streaming and an analog RCA source.Front-panel tone controlIndependent bass and treble knobs make quick system tuning simple. Simple everyday operationA compact front panel keeps power, volume, bass and treble adjustment immediately accessible without menus or an app.Best for Desktop passive-speaker systems Bookshelf speakers in small and medium rooms Simple Bluetooth stereo systems TVs or streamers with analog line output Not ideal for Systems requiring HDMI ARC, optical or USB input Users needing a subwoofer output Headphone listening EMiUZEK Buying Notes BT20A powers passive speakers; it is not intended as an input for powered speakers. The quoted 100 W × 2 is the manufacturer's maximum specification and depends on load and power supply. It has no phono stage, so most turntables require a phono preamplifier or line-level output. Frequently asked questionsCan it drive passive speakers directly?Yes. It supports 2–8 Ω passive speakers through the rear binding posts.Can it connect to active speakers?No dedicated pre-output is provided. Use BT20A to power passive speakers.Does it have a subwoofer output?No.Can I connect a turntable?Only when the turntable has a built-in phono stage or an external phono preamplifier is used.Does it support aptX?The official specification lists Bluetooth 5.0 but does not specify aptX support.Can I connect a TV?Yes, when the TV provides compatible analog audio output; there is no optical or HDMI input. HOW TO CONNECTBluetooth speaker systemSource icon: phoneSource: Phone / tabletConnection: Bluetooth 5.0Output connection: Speaker terminalsTarget icon: speakersOutput: Passive speakersWired stereo systemSource icon: streamerSource: Streamer / DAC / TV analog outputConnection: RCAOutput connection: Speaker terminalsTarget icon: speakersOutput: Passive speakers Turntable stereo systemSource icon: turntableSource: Turntable with built-in phono stage or external phono preamplifierConnection: RCA line inputOutput connection: Speaker terminalsTarget icon: speakersOutput: Passive speakersNote: Do not connect a phono-level turntable directly unless a compatible phono preamplifier is used.Technical SpecificationsInputs Feature Specification Bluetooth 5.0 Included RCA line input Included Outputs Feature Specification Stereo speaker binding posts Included Amplification Feature Specification Amplifier Architecture Class D Amplifier Chipset Dual TI TPA3116D2 Maximum Output Power 100 W × 2 Speaker Impedance 2–8 Ω Frequency Response 20 Hz–20 kHz (±1 dB) SNR ≥98 dB THD ≤0.5% Connectivity and power Feature Specification Bluetooth Range up to approximately 15 m / 50 ft without obstacles DC Input Range 12–24 V Supplied Power Adapter 24 V / 4.5 A Additional Product ContentComparison: BT20A or BT20A Pro? Feature BT20A BT20A Pro Amplifier chip Dual TPA3116D2 TPA3255 Maximum output 100 W × 2 300 W × 2 at 4 Ω Pre-out No 3.5 mm variable pre-out Best use Simple compact stereo Higher-output expandable stereo

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Fosi Audio BT20A Pro is a compact Bluetooth stereo integrated amplifier built around the TI TPA3255 for passive speakers.It adds RCA input, a variable 3.5 mm pre-out, bass and treble controls, replaceable op-amps and multiple power-supply options for a flexible desktop or room stereo system. Why it stands outTPA3255 stereo amplificationDelivers high-efficiency Class-D power with low specified distortion in a compact chassis.Variable pre-out expansionThe 3.5 mm pre-out can feed compatible powered speakers, a powered subwoofer or another amplifier.Replaceable op-ampsSocketed NE5532 op-amps allow experienced users to tailor the analog stage with compatible DIP8 replacements.Flexible power configurationsAvailable power-supply choices let buyers balance system output, size and cost. Best for Desktop and bookshelf passive-speaker systems Compact stereo systems with a powered subwoofer Bluetooth and RCA source switching Users interested in compatible op-amp rolling Not ideal for Systems requiring HDMI ARC, optical or USB input Users needing a headphone output Turntables without a phono preamplifier EMiUZEK Buying Notes Maximum power depends on the selected supply and speaker load; choose the power-supply variant appropriate for the system. The 3.5 mm connector is a pre-out, not a headphone jack. Bluetooth takes input priority; disconnect Bluetooth when using RCA if the wired source is not heard. Frequently asked questionsCan it power passive speakers?Yes. It supports 2–8 Ω passive speakers.Can it connect to a powered subwoofer?Yes, through the variable 3.5 mm pre-out using the appropriate cable.Is the pre-out a headphone output?No.Can I connect a turntable?Yes only through a turntable with line output or an external phono stage.Does it support aptX?No. The official documentation specifies SBC/AAC and states that aptX variants are not supported.Can RCA and Bluetooth play simultaneously?No. Only one input mode is used at a time. HOW TO CONNECTPassive speaker systemSource icon: streamerSource: Streamer / DAC / phoneConnection: RCA or BluetoothOutput connection: Speaker terminalsTarget icon: speakersOutput: Passive speakers2.1 stereo systemSource icon: streamerSource: Streamer / DACConnection: RCAOutput connection: Speaker terminals + 3.5 mm pre-outTarget icon: speakersOutput: Passive speakers + powered subwoofer Pre-out expansion systemSource icon: streamerSource: Streamer / DAC / phoneConnection: RCA or BluetoothOutput connection: 3.5 mm variable pre-outTarget icon: speakersOutput: Powered speakers, powered subwoofer or downstream amplifierNote: Confirm input compatibility and begin with the volume set low.Technical SpecificationsInputs Feature Specification Bluetooth 5.0 Included RCA line input Included Outputs Feature Specification Stereo speaker binding posts Included 3.5 mm variable pre-out Included Amplification Feature Specification Amplifier Chip TI TPA3255 Maximum Output Power 300 W × 2 at 4 Ω Speaker Impedance 2–8 Ω THD ≤0.005% SNR ≥108 dB Frequency Response 20 Hz–20 kHz (±1.2 dB) Socketed Op-Amps 2 × NE5532 Connectivity and power Feature Specification Bluetooth Codecs SBC / AAC Bluetooth Range up to 50 ft without obstacles DC Input Range 24–48 V Power Supply Options 32 V / 5 A or 48 V / 5 A, depending on variant Dimensions approximately 5 × 5 × 1 in Additional Product ContentComparison: BT20A or BT20A Pro? Feature BT20A BT20A Pro Amplifier chip Dual TPA3116D2 TPA3255 Maximum output 100 W × 2 300 W × 2 at 4 Ω Pre-out No 3.5 mm variable pre-out Best use Simple compact stereo Higher-output expandable stereo

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Fosi Audio MC331 is a compact tube integrated amplifier combining digital and analog source selection, speaker amplification, headphone listening and preamplifier output.Its replaceable tubes, illuminated VU meter, remote control and 105W × 2 maximum output at 4Ω make it a flexible desktop or bookshelf-speaker hub.Why it stands outAll-in-one audio hubCombines a DAC, integrated speaker amplifier, preamplifier and headphone amplifier in one compact chassis.Five source inputsAccepts Bluetooth, USB, optical, coaxial and RCA sources with remote input switching.Tube character with visual appealReplaceable 5654W-family tubes and a warm VU meter add adjustable tube character and a retro presentation.Flexible system expansionDrives passive speakers while pre-out and 3.5mm headphone outputs support additional listening configurations.Best for Desktop and small-room passive speaker systems Users switching between computer, TV, Bluetooth and analog sources Headphone and speaker listening from one compact component Listeners who enjoy replaceable tubes and VU-meter styling Not ideal for Turntables without a built-in or external phono preamp Systems requiring HDMI ARC Passive subwoofers that need a dedicated powered subwoofer channel EMiUZEK Buying Notes MC331 is an integrated amplifier and can directly drive 4–8Ω passive speakers. Its RCA input is line level; a conventional turntable requires a phono preamp. Pre-out is for an active subwoofer or downstream amplifier; it is not a passive subwoofer output. Frequently asked questionsCan MC331 drive passive speakers directly?Yes. Connect 4–8Ω passive speakers to its speaker terminals.Does it include a phono input?No. A turntable needs a built-in phono stage or a separate phono preamp before the RCA input.Can I connect a TV?Yes, through optical, coaxial or RCA audio output. MC331 does not provide HDMI ARC.Can I use headphones?Yes. It includes a front 3.5mm headphone output.Can I add a subwoofer?Yes. Use pre-out with a powered subwoofer or another compatible downstream device.Are the tubes replaceable?Yes. Officially listed compatible families include 6AK5, 6AK5W, 6Zh1P and 6J1.HOW TO CONNECTPassive speaker systemSource: Phone, computer, TV or line-level sourceConnection: Bluetooth, USB, optical, coaxial or RCAOutput: Speaker terminalsTarget: 4–8Ω passive speakersNote: Select the matching input and begin at low volume.Headphone setupSource: Digital or analog sourceConnection: Bluetooth, USB, optical, coaxial or RCAOutput: 3.5mm headphone outputTarget: Wired headphonesNote: Disconnect or lower speaker output before private listening.2.1 system with powered subwooferSource: Digital or analog sourceConnection: Chosen source inputOutput: Speaker terminals + pre-outTarget: Passive speakers + powered subwooferNote: Use the subwoofer's own level and crossover controls for integration.Technical SpecificationsCore specifications Feature Specification Product type Tube integrated DAC / amplifier / headphone amplifier Maximum speaker output 105W × 2 at 4Ω Speaker impedance 4–8Ω THD ≤0.03% SNR ≥100dB Power supply 24V / 4.5A Inputs and outputs Feature Specification Inputs Bluetooth, USB, optical, coaxial, RCA Outputs Passive speaker terminals, pre-out, 3.5mm headphone output Bluetooth codecs SBC, AAC Replaceable tubes 6AK5, 6AK5W, 6Zh1P, 6J1 Recommended System Setup Setup Connection Desktop speakers PC → USB → MC331 → Passive speakers TV audio TV optical output → MC331 → Passive speakers 2.1 system Source → MC331 → Passive speakers + powered subwoofer Additional Product ContentFosi Audio product comparisonCompare the two compact Fosi Audio integrated amplifiers by the differences that most affect system matching. Feature MC331 MC351 Product position Tube DAC / integrated stereo amplifier High-power 2.1 digital integrated amplifier Built-in speaker amplifier Yes Yes Maximum output 105W × 2 at 4Ω 165W × 2 + 350W at 4Ω Main inputs Bluetooth, USB, optical, coaxial, RCA Bluetooth 5.3, USB, optical, coaxial, RCA Speaker output Stereo passive speakers Stereo passive speakers Passive subwoofer output No Yes, dedicated amplified output Line-level pre-out Yes Yes Headphone output Yes, 3.5mm No Tube stage Yes, replaceable tubes No Best use Compact tube stereo and headphone system Powerful passive-speaker 2.1 system

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Fosi Audio GR40 is a desktop tube DAC, headphone amplifier and preamplifier for digital and Bluetooth sources.USB, optical, coaxial and Bluetooth inputs, replaceable 5654W tubes, tone controls and RCA pre-output make it a flexible centerpiece for headphones or powered audio systems.Why it stands outMulti-input desktop DACAccepts USB, optical, coaxial and Bluetooth sources in one compact component.Tube analog stageTwo replaceable 5654W tubes add tube-based amplification and visual character.Headphone and preamp operationUse the front 3.5mm headphone output or feed powered speakers and power amplifiers from RCA.High-resolution and codec supportSupports PCM 32-bit/384kHz, DSD256 and Bluetooth codecs including aptX HD and aptX LL.Best for Desktop headphone listening TVs with optical audio output Computers using USB audio Powered speakers or separate power amplifiers Not ideal for Directly driving passive speakers Balanced headphone or XLR systems Turntables without a phono preamplifier EMiUZEK Buying Notes GR40 is not a speaker power amplifier; passive speakers require a separate power amplifier. The RCA output is muted when headphones are connected. Allow the tubes to cool before removal and only use officially compatible replacements. Frequently asked questionsCan GR40 power passive speakers?No. Connect its RCA output to a separate power amplifier or use powered speakers.Can it connect to a TV?Yes, through a compatible optical or coaxial digital output.Does it include a phono input?No. A turntable requires a built-in or external phono preamplifier.Which headphones are supported?The official range is 32–300Ω through the 3.5mm output.Can the tubes be replaced?Yes, but only with compatible tube types and after the unit is powered off and cool.What Bluetooth codecs are supported?SBC, AAC, aptX, aptX HD and aptX LL are listed in the manual.HOW TO CONNECTComputer headphone systemSource icon: computerSource: Windows PC / MacConnection: USB audioOutput connection: 3.5mm headphone outputTarget icon: headphonesOutput: Wired headphonesTV headphone systemSource icon: tvSource: TVConnection: Optical or coaxial PCMOutput connection: 3.5mm headphone outputTarget icon: headphonesOutput: Wired headphonesPowered speaker or amplifier systemSource icon: streamerSource: Digital source / Bluetooth deviceConnection: USB, optical, coaxial or BluetoothOutput connection: RCA pre-outputTarget icon: speakersOutput: Powered speakers or separate power amplifierTechnical SpecificationsInputs and outputs Feature Specification Inputs USB; optical; coaxial; Bluetooth Outputs RCA pre-output; 3.5mm headphone output Channels 2.0 Tube complement 2 × 5654W Digital and headphone performance Feature Specification Maximum resolution PCM 32-bit / 384kHz; DSD256 Bluetooth 5.1; SBC, AAC, aptX, aptX HD, aptX LL Headphone impedance 32–300Ω Output power 300mW @ 16Ω; 250mW @ 32Ω; 50mW @ 250Ω; 40mW @ 300Ω SNR ≥103dB Power input DC 12V Additional Product ContentComparison: Which Fosi Audio model is right for you? Model GR40 GR70 K7 Product position Tube DAC / headphone amp / preamp Analog tube headphone amp / preamp Balanced digital DAC / headphone amp Digital inputs USB, optical, coaxial, Bluetooth None USB, optical, coaxial, Bluetooth Headphone outputs 3.5mm 3.5mm and 6.35mm 3.5mm and 4.4mm balanced Speaker-system output RCA pre-out RCA pre-out RCA line output Best use Digital sources with tube stage Analog tube headphone system High-output HiFi and gaming

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Fosi Audio BT30D is a compact 2.1-channel Bluetooth integrated amplifier for two passive speakers and a passive or powered subwoofer.Dedicated subwoofer level and crossover controls make it a straightforward way to build an adjustable small-room, desktop or TV audio system. Why it stands outTrue 2.1-channel speaker controlSeparate stereo and subwoofer amplification supports passive speakers plus a passive subwoofer from one compact unit.Passive and powered subwoofer flexibilitySpeaker-level subwoofer output and a line-level subwoofer connection support different bass-system configurations.Dedicated bass integrationSubwoofer volume and cutoff adjustment help blend low frequencies with the main speakers. Compact analog controlMaster volume, bass, treble, subwoofer level and crossover adjustment are available directly from the front panel.Best for Compact 2.1 passive-speaker systems Desktop and small-room audio Adding an adjustable subwoofer to bookshelf speakers Bluetooth or RCA playback Not ideal for Systems requiring HDMI ARC or digital audio inputs Users needing a headphone output Large high-output home-theater systems EMiUZEK Buying Notes The main left/right outputs are for passive speakers. Use the dedicated speaker output for a passive subwoofer or the line-level output for a powered subwoofer. It has no phono stage; a turntable requires line output or an external phono preamplifier. Frequently asked questionsCan it power a passive subwoofer?Yes, through the dedicated subwoofer speaker output.Can it connect to a powered subwoofer?Yes, through its line-level subwoofer output.Can it be used without a subwoofer?Yes, it can operate as a 2.0-channel amplifier for passive speakers.Can it connect to a TV?Yes when the TV provides compatible analog audio output; it has no HDMI or optical input.Can it power active speakers?The main speaker outputs are amplified for passive speakers. A compatible line-level output should be used for powered equipment.Does it include Wi-Fi streaming?No. Wireless playback is through Bluetooth. HOW TO CONNECTPassive 2.1 systemSource icon: phoneSource: Phone / streamerConnection: Bluetooth or RCAOutput connection: L/R speaker terminals + passive subwoofer terminalsTarget icon: speakersOutput: Two passive speakers + passive subwooferPowered subwoofer systemSource icon: TVSource: TV analog output / DACConnection: RCAOutput connection: L/R speaker terminals + line-level sub outputTarget icon: speakersOutput: Passive speakers + powered subwoofer Passive 2.0 stereo systemSource icon: streamerSource: Streamer / DAC / phoneConnection: RCA or BluetoothOutput connection: Left and right speaker terminalsTarget icon: speakersOutput: Two passive speakersNote: A subwoofer is optional; the BT30D can operate as a conventional stereo amplifier.Technical SpecificationsInputs Feature Specification Bluetooth 5.0 Included RCA line input Included Outputs Feature Specification Stereo passive-speaker output Included Passive-subwoofer speaker output Included Line-level output for powered subwoofer Included Amplification Feature Specification Amplifier Chipset 2 × TI TPA3116D2 Maximum Main Output 50 W × 2 Maximum Subwoofer Output 100 W Speaker Impedance 2–8 Ω Subwoofer Cutoff Adjustment 20–200 Hz Connectivity and physical Feature Specification Bluetooth Range up to 15 m / 49 ft without obstacles Dimensions 118 × 132 × 35 mm Supplied Power Adapter 24 V / 4.5 A Additional Product ContentComparison: BT30D or BT30D Pro? Feature BT30D BT30D Pro Amplifier architecture 2 × TPA3116D2 TPA3255 Maximum output 50 W × 2 + 100 W 165 W × 2 + 350 W at 4 Ω DC input range Supplied 24 V / 4.5 A 12–36 V Best use Compact moderate-output 2.1 Higher-output 2.1 systems

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Fosi Audio MC351 is a compact 2.1-channel integrated digital amplifier for passive stereo speakers and a passive subwoofer.Dual TI TPA3255 amplifier chips, broad digital and analog inputs and up to 165W × 2 + 350W at 4Ω make it a practical control center for powerful 2.1 systems.Why it stands outDedicated 2.1 amplificationSeparate stereo and passive-subwoofer amplification builds a complete 2.1 system without a second power amp.Dual TPA3255 architectureTwo TI TPA3255 amplifier chips provide high output for speakers and a passive subwoofer.Broad source compatibilityBluetooth 5.3, USB, optical, coaxial and RCA inputs cover common music, computer and TV sources.System expansion through pre-outThe pre-out connection supports a powered subwoofer or compatible downstream equipment.Best for Passive bookshelf or floorstanding speaker systems 2.1 systems using a passive subwoofer TV and desktop systems using optical, coaxial or USB audio Users who need both wireless and wired source inputs Not ideal for Users needing HDMI ARC or TV-remote CEC control Headphone-only systems Turntables without a built-in or external phono preamp EMiUZEK Buying Notes MC351 directly powers passive speakers and a passive subwoofer; these are different from line-level active speakers. USB is an audio-data input, not a power input. RCA is line level and does not replace a phono preamp for a standard turntable. Frequently asked questionsCan MC351 drive passive speakers?Yes. It is designed for 4–8Ω passive speakers.Can it power a passive subwoofer?Yes. It has a dedicated amplified passive-subwoofer output.Can I connect a powered subwoofer?Yes. Use the line-level pre-out with a compatible powered subwoofer.Does it support HDMI ARC?No. Use optical, coaxial or RCA audio from a television.What does the USB port do?It receives USB digital audio from a compatible computer or source; it does not power the amplifier.Can I connect a turntable?Only if the turntable has a built-in phono preamp or you add an external phono preamp.HOW TO CONNECT2.1 passive speaker systemSource: Computer, streamer or TVConnection: USB, optical, coaxial, RCA or BluetoothOutput: Speaker terminals + passive-subwoofer outputTarget: Passive speakers + passive subwooferNote: Match speaker impedance and begin with low volume.Stereo speaker systemSource: Any supported digital or analog sourceConnection: Chosen inputOutput: Left/right speaker terminalsTarget: 4–8Ω passive speakersNote: Leave the passive-subwoofer output unused for a 2.0 system.System with powered subwooferSource: Any supported sourceConnection: Chosen inputOutput: Speaker terminals + pre-outTarget: Passive speakers + powered subwooferNote: Set crossover and level on the powered subwoofer.Technical SpecificationsCore specifications Feature Specification Product type 2.1-channel integrated digital amplifier Amplifier chips TI TPA3255 × 2 Maximum output 165W × 2 + 350W at 4Ω Speaker impedance 4–8Ω THD ≤0.03% SNR / Dynamic range ≥100dB / ≥100dB Power input range DC 24–48V Inputs and outputs Feature Specification Inputs Bluetooth 5.3, USB, optical, coaxial, RCA Outputs Passive speakers, passive subwoofer, pre-out USB sampling Up to 24-bit / 96kHz Optical / coaxial sampling Up to 32-bit / 192kHz Frequency response 20Hz–20kHz (±0.5dB) Subwoofer output range 20Hz–250Hz Recommended System Setup Setup Connection 2.1 passive system Source → MC351 → Passive speakers + passive subwoofer TV system TV optical output → MC351 → Passive speakers Powered sub expansion Source → MC351 → Passive speakers + pre-out → Powered subwoofer Additional Product ContentFosi Audio product comparisonCompare the two compact Fosi Audio integrated amplifiers by their power, output structure and intended system layout. Feature MC351 MC331 Product position High-power 2.1 digital integrated amplifier Tube DAC / integrated stereo amplifier Built-in speaker amplifier Yes Yes Maximum output 165W × 2 + 350W at 4Ω 105W × 2 at 4Ω Main inputs Bluetooth 5.3, USB, optical, coaxial, RCA Bluetooth, USB, optical, coaxial, RCA Speaker output Stereo passive speakers Stereo passive speakers Passive subwoofer output Yes, dedicated amplified output No Line-level pre-out Yes Yes Headphone output No Yes, 3.5mm Tube stage No Yes, replaceable tubes Best use Powerful passive-speaker 2.1 system Compact tube stereo and headphone system

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Fosi Audio T20 is a compact Bluetooth tube integrated amplifier for passive speakers and wired headphones.It combines 50W x2 Class D speaker power with replaceable vacuum tubes, RCA input and tone controls for a warm, flexible desktop stereo system. Why it stands outFour reasons this product deserves a place in a well-planned audio system.Tube-Buffered SoundReplaceable vacuum tubes add the tube stage and allow compatible tube rolling.Speaker and Headphone ListeningThe T20 powers passive speakers and also provides a front 3.5mm headphone output.Bluetooth and RCA InputsSwitch between convenient wireless playback and a conventional analog source.Compact Tone ControlIndependent bass and treble controls make it easier to adapt the system to speakers, headphones and room acoustics. Best for Desktop passive-speaker systems Bluetooth music playback Headphone and speaker listening from one compact amplifier Listeners interested in compatible tube rolling Not ideal for Users requiring optical, USB or HDMI inputs Balanced XLR audio systems Turntables without a built-in or external phono preamp Users needing a dedicated subwoofer output EMiUZEK Buying Notes T20 is an integrated speaker amplifier and can directly drive compatible 4–8Ω passive speakers. Its RCA input is line level; a conventional turntable requires a separate phono preamplifier. The 3.5mm jack is a headphone output, not a microphone connection. Frequently Asked QuestionsCan the T20 drive passive speakers directly?Yes. Connect a compatible 4–8Ω passive speaker pair to the rear speaker terminals.Can I connect a turntable?Yes only when the turntable has a built-in phono preamp or is used with an external phono preamp.Does it work as a headphone amplifier?Yes, it includes a front 3.5mm headphone output.Does it accept digital audio?No. Inputs are Bluetooth and analog RCA; optical and USB audio are not provided.Can the tubes be replaced?Yes. Use only compatible tube types and power the unit off before replacement.Does it have a subwoofer output?No dedicated subwoofer output is specified. Use a subwoofer integration method supported by your wider system. HOW TO CONNECTBluetooth speaker systemSource: Phone / tabletConnection: BluetoothOutput: Speaker terminalsTarget: Passive speakersNote: Pair the source and set volume low before playback.Wired stereo systemSource: DAC / streamer / CD playerConnection: RCA line inputOutput: Speaker terminalsTarget: Passive speakersNote: Use a fixed or controlled line-level source.Headphone listeningSource: Phone via Bluetooth or RCA sourceConnection: Bluetooth / RCAOutput: 3.5mm headphone outputTarget: Wired headphonesNote: Lower volume before inserting headphones. Technical SpecificationsAmplifier Feature Specification Product Type Bluetooth tube integrated amplifier Amplifier Chip TI TPA3116 Maximum Speaker Output 50W x2 at 4Ω Speaker Impedance 4–8Ω Connectivity Feature Specification Inputs Bluetooth 5.0; RCA line input Outputs Passive speaker terminals; 3.5mm headphone Tone Controls Bass and treble Audio Feature Specification Vacuum Tubes Replaceable 6K4 pair Frequency Response 20Hz–20kHz (±1.5dB) THD ≤0.04% SNR ≥99dB Recommended System Setup Setup Connection Wireless stereo Phone → Bluetooth → T20 → passive speakers Wired stereo Streamer/DAC → RCA → T20 → passive speakers Headphones Source → T20 → 3.5mm headphones Additional Product Content Feature T20 T20X P3 Product Position 50W x2 tube integrated amp 100W x2 tube integrated amp Tube preamp / headphone amp Passive Speaker Amplifier Yes Yes No Inputs Bluetooth 5.0, RCA Bluetooth, AUX Bluetooth, RCA Speaker Output 50W x2 max at 4Ω 100W x2 max at 4Ω None Headphone Output 3.5mm 3.5mm 3.5mm Tone Controls Bass, treble Bass, treble Bass, treble Tube Rolling Compatible tubes Compatible tubes Compatible tubes Best Use Compact speaker/headphone system Higher-power speaker system Add tube preamp/headphone stage

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Fosi Audio T20X is a Bluetooth vacuum-tube integrated amplifier for passive speakers and wired headphones.Its upgraded 100W x2 output, replaceable tubes and bass/treble controls create a compact all-in-one amplifier for desktop and bookshelf systems. Why it stands outFour reasons this product deserves a place in a well-planned audio system.100W x2 Maximum OutputThe Class D power stage provides more headroom than the T20 for compatible passive speakers.Replaceable Tube StageTube rolling lets experienced users experiment with compatible tube options.Two Listening OutputsDrive passive speakers or use the 3.5mm headphone connection from the same amplifier.Simple Wireless and Analog PlaybackBluetooth and analog input cover the most common phone, streamer and DAC setups without a complex interface. Best for Bookshelf passive-speaker systems Bluetooth desktop audio Combined speaker and headphone listening Listeners wanting tube character with higher output than the T20 Not ideal for Users requiring optical, USB or HDMI audio Balanced XLR systems Turntables without phono amplification Systems needing a dedicated subwoofer output EMiUZEK Buying Notes T20X is an integrated amplifier and can directly drive compatible 2–8Ω passive speakers. Its analog input is line level; use a phono preamp with a conventional turntable. The maximum output figure depends on speaker impedance, supply voltage and test conditions. Frequently Asked QuestionsCan the T20X drive passive speakers?Yes. It is an integrated amplifier with passive-speaker outputs.Can it connect to a turntable?Yes when the turntable has a built-in phono preamp or an external phono preamp is used.Does it include a headphone output?Yes, a 3.5mm wired headphone output is provided.Does it support optical or USB audio?No. Use Bluetooth or the analog input.Can the vacuum tubes be replaced?Yes. Use compatible tubes and switch the amplifier off before tube replacement.Can I connect an active subwoofer?No dedicated subwoofer output is specified; use a compatible system-level integration method. HOW TO CONNECTBluetooth stereoSource: Phone / tabletConnection: BluetoothOutput: Speaker terminalsTarget: Passive speakersNote: Keep initial volume low when pairing.Wired HiFiSource: Streamer / DAC / CD playerConnection: Analog line inputOutput: Speaker terminalsTarget: Passive speakersNote: Use a line-level source.Headphone systemSource: Bluetooth or analog sourceConnection: Bluetooth / line inputOutput: 3.5mm headphone outputTarget: Wired headphonesNote: Disconnect or lower speaker listening as appropriate. Technical SpecificationsAmplifier Feature Specification Product Type Bluetooth tube integrated amplifier Amplifier Chip TI TPA3221 Maximum Output 100W x2 at 4Ω Speaker Impedance 2–8Ω Audio Feature Specification Frequency Response 20Hz–20kHz (±1dB) THD ≤0.3% SNR ≥86dB Input Sensitivity ≤650mV Connectivity and Power Feature Specification Inputs Bluetooth; analog line input Outputs Passive speaker terminals; 3.5mm headphone Power Supply 24V/4.5A included DC Input Range 12–30V Recommended System Setup Setup Connection Wireless speaker system Phone → Bluetooth → T20X → passive speakers Wired stereo Streamer/DAC → line input → T20X → passive speakers Headphones Source → T20X → 3.5mm headphones Additional Product Content Feature T20X T20 P3 Product Position Higher-power tube integrated amp Compact tube integrated amp Tube preamp / headphone amp Passive Speaker Amplifier Yes Yes No Maximum Speaker Output 100W x2 at 4Ω 50W x2 at 4Ω Not applicable Inputs Bluetooth, line input Bluetooth 5.0, RCA Bluetooth, RCA Headphone Output 3.5mm 3.5mm 3.5mm Tone Controls Bass, treble Bass, treble Bass, treble Tube Rolling Compatible tubes Compatible tubes Compatible tubes Best Use More speaker headroom Compact speaker system Existing amplifier / active speakers

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RAKOSO HA400 is a professional 4-zone network streaming amplifier designed for whole-home audio systems, commercial background music installations, and multi-room speaker setups. With four independent amplifier zones, network streaming support, AirPlay 2, Spotify Connect, multi-room control, and flexible audio inputs and outputs, HA400 provides a complete solution for powering and managing multiple speaker areas from a single device. Each zone delivers 50W × 2 stereo amplification at 8Ω or 100W bridge mode output at 4Ω, allowing direct connection to passive speakers without additional power amplifiers.  Why it stands out Four-Zone Amplification System HA400 combines four independent streaming amplifiers into one centralized audio system. Four separate audio zones 50W × 2 stereo output per zone Bridge mode up to 100W Direct connection to passive speakers Complete Whole-Home Audio Solution Control multiple rooms from one device. Play different music in different zones Synchronize all zones together Manage playback through the 4STREAM app Suitable for residential and commercial installations Modern Network Streaming HA400 supports popular streaming platforms and network protocols. AirPlay 2 Spotify Connect DLNA UPnP Qplay Internet music services Professional Installation Features Designed for advanced audio installations. Rack-mountable design RS232 smart control integration 12V trigger support Multiple digital and analog connections Best for Whole-home audio systems Multi-room speaker installations Commercial background music systems Restaurants, offices, and retail spaces Professional custom audio projects Not ideal for Users looking for a simple single-room amplifier Desktop audio systems Users needing a portable streaming device Users without multiple speaker zones EMiUZEK Buying Notes RAKOSO HA400 is a multi-zone streaming amplifier with built-in amplification. Each zone can directly drive passive speakers. External power amplifiers are not required for normal installations. Speaker impedance and wiring should match the amplifier output specifications. Designed mainly for whole-home and professional installations rather than simple personal audio setups. FAQ Can RAKOSO HA400 directly power passive speakers? Yes. HA400 includes four built-in amplifier zones and can directly drive passive speakers. Typical setup: Streaming Source → HA400 → Passive Speakers How many rooms can RAKOSO HA400 control? HA400 supports four independent audio zones. Each zone can play different content or synchronize with other zones. Can different rooms play different music at the same time? Yes. Each zone can operate independently through the 4STREAM application. Does RAKOSO HA400 support AirPlay 2? Yes. HA400 supports AirPlay 2 for wireless streaming from compatible Apple devices. Does RAKOSO HA400 support Spotify Connect? Yes. HA400 supports Spotify Connect for direct network streaming. What speakers can be used with RAKOSO HA400? HA400 supports passive speakers connected directly to each amplifier zone. Each zone provides: 50W × 2 @ 8Ω stereo mode 100W bridge mode @ 4Ω Can RAKOSO HA400 be installed in a rack? Yes. HA400 is designed for professional installations and supports rack mounting. Can RAKOSO HA400 integrate with smart home systems? Yes. HA400 supports RS232 control for integration with compatible automation systems. HOW TO CONNECT Whole Home Audio Setup Source icon: Streaming ServicesSource: AirPlay / Spotify / Network MusicConnection: WiFi / EthernetOutput connection: Speaker OutputTarget icon: speakersOutput: Multiple Passive Speakers Note: Build a complete multi-room audio system. Individual Zone Setup Source icon: smartphoneSource: Streaming AppConnection: NetworkOutput connection: Zone Speaker OutputTarget icon: speakersOutput: Passive Speakers Note: Control each room independently. Professional Installation Setup Source icon: Smart Home ControllerSource: Automation SystemConnection: RS232Output connection: HA400Target icon: Multi-zone Speakers Note: Integrate HA400 into custom audio systems. Technical Specifications Amplifier Feature Specification Product Type 4-Zone Network Streaming Amplifier Amplifier Type Class D Number of Zones 4 Output Power 50W × 2 @ 8Ω per zone Bridge Mode 100W @ 4Ω per zone Speaker Output Passive Speakers Streaming & Connectivity Feature Specification WiFi 2.4GHz Ethernet RJ45 Bluetooth Supported Streaming Protocols AirPlay 2 / Spotify Connect / DLNA / UPnP / Qplay Multi-Room Supported Audio Inputs Feature Specification Analog Input RCA Digital Input Optical / Coaxial USB USB Storage Playback Audio Outputs Feature Specification Speaker Output 4 Zones Pre Output RCA Digital Output Optical / Coaxial Subwoofer Output Supported Audio Performance Feature Specification Audio Decode Up to 24-bit / 192kHz Supported Formats FLAC / MP3 / AAC / AAC+ / ALAC / APE / WAV Frequency Response 20Hz–20kHz THD+N 0.03% SNR 93dB Control Feature Specification App Control 4STREAM App Smart Home Control RS232 Trigger 12V Trigger Recommended System Setup Setup Connection Whole Home Audio Network → HA400 → Multiple Speaker Zones Commercial Audio Streaming Source → HA400 → Ceiling Speakers Multi-Room Setup 4 Zones → Different Rooms What's in the box RAKOSO HA400 ×1 Rack Mount Accessories ×1 Power Cable ×1 User Manual ×1 EMIUZEK Download Center Access product manuals, firmware updates, and additional support resources. RAKOSO HA400 manuals and downloads: https://emiuzek.com/pages/download Additional Product Content RAKOSO HA400 vs RAKOSO H400 Feature HA400 H400 Product Position 4-Zone Streaming Amplifier 4-Zone Streaming Preamplifier Built-in Amplifier Yes No Speaker Output Yes No External Amplifier Required No Yes Zones 4 4 AirPlay 2 Yes Yes Spotify Connect Yes Yes Best Use Complete multi-room speaker system Existing amplifier installations

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