BT20A
amplifier
$80
Used market: $60*
Specifications
3 of 6 values have a recorded sourceExpert Audio Engineering Commentary
Headroom Notes
The plain BT20A, not the BT20A MAX already in this catalogue: a 24 V / 4.5 A supply, ATS2853 Bluetooth, and 100 W x 2 into 4 ohms across 20 Hz - 20 kHz at 0.04 % THD. Fosi's description also invites you to drive '280 watts (8 ohms) and 320 watts (4 ohms)' speakers, which is a statement about the speakers' power handling and not about what this amplifier delivers into them.
Thermal Behavior
Same page layout, same numbers and the same internal contradiction as Fosi's TB10A: the load range of 2 - 8 ohms is stated only in the specification table, and the distortion figure differs between the table and the description.
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.
«Specifications: THD ≤ 0.5%; Output power 100W + 100W — against the description above it: '100W X 2(4 ohms, 20 Hz - 20 kHz, 0.04% THD)'»
The specification table gives the power without naming a load and the distortion as ≤ 0.5 %, while the description above gives the same power into 4 ohms at 0.04 % - a twelvefold difference in the distortion limit on one page. Fosi repeats this layout across the TB10A and the T20; only the description carries the measurement conditions.
checked 8/5/2026* Estimated with the depreciation fallback (~75% retained value). · checked on 8/5/2026