TB10D
amplifier
$80
Used market: $60*
Specifications
3 of 5 values have a recorded sourceExpert Audio Engineering Commentary
Headroom Notes
The stored rating is the one Fosi's own text attaches conditions to: 300 W per channel into 4 ohms at 10 % THD. Ten per cent is the clipping point, not a listening condition; the same sentence gives 150 W per channel into 8 ohms 'unclipped', which is the figure worth planning around. The specification table separately prints 'THD <= 0.3 %' with no power attached, so the two cannot be combined.
Thermal Behavior
'Terminating Impedance 2-8 ohms' - a published two-ohm floor, which almost nobody in this catalogue states. Believe it only together with the supply: the box ships a 32 V / 5 A brick, and Fosi says the 300 W figure needs 48 V / 10 A. At 32 V / 5 A the amplifier cannot draw more than 160 W from the wall no matter what the load is.
What the datasheet actually says
Quoted verbatim from the manufacturer’s own page, with the date we checked it. We state what is printed, not what anyone intended by it.
«The device is operated in AD-mode, and can drive up to 2 x 300 W into 4-Ω load at 10% THD and 2 x 150 W unclipped into 8-Ω load. ... What you Get: TB10D amplifier x1, User Manual x1, 32V/5A Power Adapter x1 (Note: You need a more powerful power supply to get the MAX 300W x2 power output, such as 48V/10A.)»
The product title says 300W x2 and the specification table repeats it, but both conditions that make it true are outside the table. First, 10 % distortion: that is the point at which the waveform is visibly clipped, roughly twice the usable power. Second, a power supply that is not in the box - Fosi says so itself, in the packing list. With the supplied 32 V / 5 A adapter the amplifier can draw at most 160 W from the wall, so 600 W of output is not merely optimistic, it is unavailable until you buy a second brick. The 150 W per channel into 8 ohms 'unclipped' in the same sentence is the number that survives both conditions.
checked 8/5/2026* Estimated with the depreciation fallback (~75% retained value). · checked on 8/5/2026