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In addition to the unpowered analog output to your speakers, Fosi also included a proper 3.5mm PRE-OUT on the BT20A Pro. You can use it to connect a powered subwoofer or speaker but you can also use it as a preamp and attach it to a power amplifier. That lets you use the volume, treble and bass to control the audio, passing on all the work to the power amp. With 300W available already you may never need to make use of it. Seeing it on an amp of this cost is a very nice bonus. This level of control is especially useful for those who are particular about their audio setup and want to tweak the tonality. Overall, the Fosi Audio TB10D offers outstanding value and I highly recommend it for anyone building a modest or secondary stereo system. The TB10D sounds pretty good, honestly better than its price would suggest. The power is clean, and with the tone control you can get some warmth in the mids to hide some of that Class D brightness if you already have brighter speakers. The vocals are pleasant and the bass is pretty tight. The top end does well to add some sparkle to the sound. Depending on what speakers you pair this amp with you may not miss having a subwoofer too much. With plenty of power, the Monitor 5s were certainly reaching deep.
AIYIMA A07 TPA3255 vs Fosi Best budget mini class D amp? AIYIMA A07 TPA3255 vs Fosi
Bluetooth implementation is clean - IMO this is better than the A07 Pro (which was very noisy in the model I have)
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Inside is a class D amplifier based around the TPA3255 chipset from Texas Instruments, data sheet Here for anyone interested. The TPA3255 is a high-power, 4-channel amplifier that can be run in a stereo BTL mode as it is here for higher current delivery and power output.
Fosi Audio TB10D TPA3255, Is That An Amp In Your Pocket? Fosi Audio TB10D TPA3255, Is That An Amp In Your Pocket?
d. Having correct instrumental timbre - that is, each instrument's tonal qualities are accurately showcased, often-times also referred to as “being musical.” Still not sure which one I like best, overall they both sound great, just slightly different. I will be testing them further when my new Elac debut b6 speakers come in the mail. One thing that is not often discussed regarding mini class-D amps is thermal management. I was planning to delve further into this issue. I encountered multiple thermal protections being triggered on the chip while using it at full power (160w rms 2ch) on 4 ohm loads for about 5 minutes. The enclosure was warm, but not hot. However, when I ran the amp again with the PCB exposed, I was able to measure the temperature of the aluminum heatsink.
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The TPA3255 specifies a mere 0.006% total harmonic distortion plus noise (THD+N) at 1W into a 4Ω load, rising to just 0.1% at the onset of clipping. Power supply ripple rejection is >65dB at 1kHz in BTL mode, so the chip isn’t especially sensitive to a quality power supply. The chip is 90% efficient at 4Ω
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