Fosi Audio TB10D TPA3255, Is That An Amp In Your Pocket?

Manufacturer: Fosi Audio Fosi Audio TB10D TPA3255, Is That An Amp In Your Pocket?

This is the first time we have taken a look at a Fosi Audio product at PCPer; not even a link to someone’s review on another site.  They are a Chinese company which somewhat recently expanded their business overseas.  They specialize in “Hi-Fi products, DIY kits and DIY guidance for audiophiles“.  Their products include amps and pre-amps for passive speakers or headsets, DACs, Bluetooth receivers, and even some DIY kits, all at a non-audiophile price point.

What we have here is the TB10D TPA3255, a stereo power amplifier with basic treble, bass and volume controls.  While it is barely the size of a paperback book it is has two analog channels each of which are capable of driving up to 315 W into a 4-Ω load at 10% total harmonic distortion or two 150 W unclipped into an 8-Ω load.   It is up against a venerable Kenwood KR-V87R stereo tuner/amp, and will be attached to five pairs of 8-Ω speakers sporting a variety of maximum wattages, all over 100W.

Product Specifications
  • Model Number: TB10D TPA3255
  • Compatibility: Banana plug or bare wire
  • Output Power:
    • 300 Watts x2@4Ω
    • Terminating Impedance: 2Ω – 8Ω
  • Input Mode: RCA
  • Output Mode: Passive Speakers
  • Audio Specifications:
    • Frequency Range: 20Hz – 40kHz (±1 dB)
    • THD: ≤ 0.3%
    • SNR: ≥ 90dB
    • Signal: Analog
  • Chipset: TPA3255
  • Dimensions: 150 x 110 x 40 mm / 5.9 x 4.3 x 1.6 inches
  • Overall Weight: 1.05kg
  • Power: 32V 5A External Power Supply

$82.99 USD list, currently $74.99 

Manufacturer Description

“If you want to play your favorite songs entertainingly, a mini stereo amplifier is the best way to go. Fosi Audio TB10D is an analog input(RCA) Class-D audio amplifier that easy to install to build your home audio sound system.  MAX Power Output up to 600Watts. TB10D adopts TI TPA3255 high-performance Class-D power amplifier chip enabling true premium sound quality. TPA3255 features an advanced integrated feedback design and proprietary high-speed gate driver error correction (PurePath Ultra-HD). This technology allows ultra low distortion across the audio band and superior audio quality. The device is operated in AD-mode, and can drive up to 2 x 315 W into 4-Ω load at 10% THD and 2 x 150 W unclipped into 8-Ω load.”

Good Things Come In Small Packages

A tiny stereo amplifier designed to be connected to unpowered speakers seems an odd thing, as you aren’t often called upon to produce an amp while you are out and about, except perhaps a headphone amp which the Fosi Audio TB10D TPA3255 is not.  Then again, there is an attractiveness to having a portable 600W amp, or one that takes up a minuscule amount of space on a shelf.  Considering the variety of products Fosi Audio sells there must be something to this.

The $75 cost to purchase it is certainly in it’s favour, much less expensive than some more traditional stereo amps, especially those with more than just two channels.  The specifications are another interesting feature, this Class-D amplifier is powered by a Texas Instruments TPA3255 chipset that provides a PurePath Ultra-HD signal with very low distortion.   It is hard to complain about a frequency range of 20Hz – 40kHz nor a signal to noise ratio of 90dB.  It is also kind of cute in an industrial sort of way though the phono pre-amp with vacuum tubes beats the TB10D TPA3255 in that department.

A Very Pleasant Surprise

The poor ancient Kenwood, which is over 30 years old, has been powering a variety of my speakers for several decades.  Over that time it has developed some grounding issues and the higher end intermittently becomes quite muffled making movie dialog a little hard to hear.  As percussive maintenance and a quick flick to the equalizer resolves these problems, it has stuck around as it is still just good enough.  There is also the fact that many modern amps do not have posts for bare wires, so an upgrade would likely involve new speakers as well as an amp.   It also sports front and rear channels in addition to left and right, as well as one of the first incarnations of Dolby Surround, neither of which is provided by the Fosi TB10D TPA3255.

After a bit of work, the wire transplant was successful and the TB10D TPA3255 is ready to try powering an obnoxious amount of speakers.  A flick of the power button and suddenly the room is filled with clearer and louder sound than it has been since I last pulled my NAD amp out for testing.  The signal is just stereo, with no front nor rear channels but there was no question those channels were perfectly separated and fully audible all around the room.

The audio is not delayed at all compared to the source, though it certainly does overwhelm it.  The amp offers very clean voice performance for watching TV, and there is no question the treble and bass switches do exactly as much as you’d expect.  When swapping over to movies, the separation continues with the effects being just as loud as you like while not fuzzing out dialogue.  The amp really shines when you fire up your favourite music, with very clear audio.  Those that prefer a warm tone might not favour the TB10D TPA3255, as it doesn’t have quite the same warmth as the old Kenwood.  The lack of Dolby Surround is telling, but that would not matter at all if these were used in a more normal fashion and hooked up to a pair of high end bookshelf speakers.

can you read me


By their very nature audio reviews are qualitative and not quantitative, so your ears may not agree with mine.  In this case I was able to garner a second opinion from a musician friend who has so far refused to try out the Monoprice headphones as they don’t cost $500 and so won’t be anywhere near the quality of his Sennheiser headphones.   His first comment was to congratulate me on making the Kenwood sound acceptable again.  When I explained that we were listening to the Fosi Audio TB10D TPA3255 which we both originally questioned the usage of; “titillating” was his response.

If his monitors weren’t powered, something like this would make a lot of sense.  Clean sound and a tiny footprint on the desk are both valuable attributes.  If you have a nice pair of bookshelf speakers, or another setup which just wants a stereo signal then for the price this amp is a great solution.  You probably shouldn’t use it the way I have, but it can certainly handle it with no noise or distortion though upgrading to a 48V/10A power supply is recommended to get the best experience .  The build quality is such that you can take it on the road without worry as well, for after all it is billed as a pocket amp.


Review Disclosures

This is what we consider the responsible disclosure of our review policies and procedures.

How Product Was Obtained

The product is on loan from Fosi Audio for the purpose of this review.

What Happens To Product After Review

The product remains the property of Fosi Audio but is on extended loan for future testing and product comparisons.

Company Involvement

Fosi Audio had no control over the content of the review and was not consulted prior to publication.

PC Perspective Compensation

Neither PC Perspective nor any of its staff were paid or compensated in any way by Fosi Audio for this review.

Advertising Disclosure

Fosi Audio has not purchased advertising at PC Perspective during the past twelve months.

Affiliate Links

This article contains affiliate links to online retailers. PC Perspective may receive compensation for purchases through those links.

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About The Author

Jeremy Hellstrom

Call it,, or PC Perspective, Jeremy has been hanging out and then working with the gang here for years. Apart from the front page you might find him on the BOINC Forums or possibly the Fraggin' Frogs if he has the time.


  1. Kent Burgess

    I do like to see analog bass and treble controls on a speaker amp of this size.

  2. Operandi

    Class D has made huge improvements in the last 10 years or so and Ti look to have one of the best budget chips on the market and this Fosi seems like really good implementation of that chip. A few things in this review though…

    The power ratings on these budget class D amps tend to be pretty meaningless, as they are going by the max specs of the chipset assuming max input voltage and with no regards to distortion. You can do the math on the included PS and get rough idea of what its theoretically capable of and its nowhere near the numbers disused in this review. Even thats pretty meaningless though because spec sheet power ratings and real world usable power are really different things. That said these amps still have plenty of real world usable power but to get an idea of what more realistic class D amp looks like look something like the ICEpower 200ASC board. Thats a 200watt @ 4ohms single channel board with onboard PS and its several orders of magnitude larger and more expensive, and thats just the single channel module.

    I also think you Kenwood is probably on its way out :(. If you are experiencing enough frequency drop off you need to EQ it something internally is certainly dying and most likely has other issues going on that make a pretty bad reference point to compare other amps.

    • Jeremy Hellstrom

      But the Kenwood has been a friend for decades, how can I toss it out just because it’s getting cranky in it’s old age?

      The power rating info is interesting. The one it shipped with is 32V @ 5A, in order to max out they recommend 24V @ 8A or 32V @ 6A … and as you say, the wattage calculation is more or less meaningless. Good to know if I do future ones.

      • Operandi

        Put it on the shelf and pull it out whenever you feel nostalgic?

        Seriously though even if the Kenwood was good as new it would still get blown away by a modern class AB or class D. I have the Adcom GFA-545 that a grew up with as a kid around and I while I do take it out now and then I prefer my modern amps and the Adcom is budget audiophile legend and a beast of a amp.

        Old shit isn’t really that great, even the hyped stuff like the Adcom. Weather that be because of degradation over time or nostalgia clouding your memory (probably both). This holds double true for speakers btw, *hint, hint*.

        • Operandi

          *would still get blown away by*

          How is editing not a thing with this software?? Com’on guys!

          • Jeremy Hellstrom


        • Alicia

          I hope your right. I am an old school set up lover. I have a technics equalizer from late 80s, a Marantz receiver from the late 70s and a Sony amp from early 90s connected to two Peavy 12s. I have two old school Kenwood passive with 140w capability and I just purchased this small 600w amp to use with them and my desktop for a office setup. So I am not a fan of the new bluetooth noise. I guess the warmth your referring too. I don’t like high pitched treble ‘noise, of bluetooth spund i like a mono sound and phono output. I like low bass but enough treble to hear the vocals well over it. But I am trying this because I don’t have another old school amp laying around and ebay can be sketchy. Thanks for the review.

    • Jeremy Hellstrom

      Nice to see what someone with the right equipment measured. I also like it when they agree with me! 🙂

  3. Greg

    Any recommendation for an upgraded power supply from a U.S. based distributor? Something in the 36v + range.


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