The review of the Fosi Audio BT20A Pro stereo class D amplifier based on the TI TPA3255 IC, priced at $99.99 with a 32-volt power supply, I’ll delve into the details and measurements.
Despite its affordable price, the amplifier’s case imparts a sense of quality. Normally skeptical of tone controls in low-cost amps due to their inability to achieve a flat response, I found that Fosi has ensured their proper functionality in this instance. A robust power switch governs its power, and the company also provided an optional 48-volt supply for an additional $40, adding to the amplifier’s capabilities.
Notably, Bluetooth input is supported, adding versatility to its features. An orange volume control knob is included, providing a pop of color to the unit.
Moving on to the measurements, the tests are conducted at 48 volts unless specified otherwise, as there was a mistaken assumption about the standard voltage being 32 volts. The dashboard reveals impressive channel matching and excellent SINAD, indicating low noise and distortion.
The amplifier performs consistently well with a 32-volt supply, securing its position in the “very good” category among amplifiers, regardless of price, as seen in the comprehensive dashboard.
Examining the competition in a zoomed-in view, the signal-to-noise ratio (SNR) holds up well for its class. Load/impedance dependency, typical in switching amplifiers, shows peaking mostly out of band, which is a positive characteristic.
Given the presence of tone controls, any peaking can be adjusted using the treble control, providing a satisfactory solution. Despite this, the frequency response remains relatively flat in the audible band with the treble and bass controls set to their detent, center position.
Multitone performance is commendable for its class, and crosstalk is notably good. Moving on to power measurements into 4 ohms with a 48-volt supply, the amplifier demonstrates the ability to deliver substantial watts, especially in short-term testing.
Switching to a 32-volt supply reduces the output, suggesting that the larger power supply likely has more capacitor reservoirs.
There is a noticeable reduction in power, as expected. The transfer function impressively maintains smoothness, and there is minimal pop-on but a discernible pop-off.
In conclusion, the TI TPA3255 platform, when implemented well as demonstrated in the Fosi Audio BT20A Pro, proves to be a capable amplifier. The amplifier’s usability is enhanced by its high-quality case and controls, particularly in setting the tone controls to flat. The power output, especially with the robust 48-volt power supply, showcases the advancements in amplification density.
As a noteworthy aside, the company has been a pleasure to work with, demonstrating exceptional politeness, cordiality, and patience throughout the testing and evaluation process. Their commitment to internal R&D is evident in the product’s performance.
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