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Fosi Audio V3 Budget Audiophile Class-D Stereo Power Amplifier (48V)

Fosi Audio V3 Budget Audiophile Class-D Stereo Power Amplifier (48V)

R 3,195.00 ZAR
R 3,195.00 ZAR
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The V3 is the latest class-D stereo power amplifier from Fosi Audio. This budget audiophile amplifier competes with much pricier amps like the Marantz PM-90 (R18,000) on signal-to-noise ratio.

Reviews

"The best amp under $400" — CheapAudioMan Review.

“State of the art DACs run on highly performant silicon that when well implemented, produces the best performance we have seen. We are seeing similar development with these class D IC amplifiers. Noise and distortion is quite low and beats many amplifiers in the market.” — Audio Science Review.

Specifications

  • 88dB – this means the signal-to-noise and distortion ratio:
    {\displaystyle \mathrm {SINAD} =10\log _{10}{\frac {P_{\text{signal}}+P_{\text{noise}}+P_{\text{distortion}}}{P_{\text{noise}}+P_{\text{distortion}}}},}
  • SnR: 110dB (signal-to-noise ratio)
    {\displaystyle \mathrm {SNR} ={\frac {P_{\mathrm {signal} }}{P_{\mathrm {noise} }}},}
  • THD+N: 0.003% (Total Harmonic Distortion + Noise) — this measures the "purity" of the signal by dividing the RMS amplitude of all the harmonics by the amplitude of the original signal (V_1), of fundamental frequency.
    • THD:
      {\displaystyle \mathrm {THD_{F}} ={\frac {\sqrt {V_{2}^{2}+V_{3}^{2}+V_{4}^{2}+\cdots }}{V_{1}}},}
    • THD+N is similar to THD but also includes noise:
      {\displaystyle {\text{THD+N}}={\frac {\displaystyle \sum _{n=2}^{\infty }{\text{harmonics}}+{\text{noise}}}{\text{fundamental}}}.}
  • Dynamic Range: 110dB at full power (14-17 bits distortion-free range)

88dB SINAD is on par with the Marantz PM-90. There are amplifiers with better SINAD, but they are 5-10x the price.

Audio Science Review Power Output Measurements:

  • Single channel driven:
    • 159Wpc into 4-ohm nominal
    • 89Wpc into 8-ohm nominal
  • Both channels driven into 4-ohm nominal:
    • 141W continuous / 2 = 70.5Wpc sustained
    • 190W peak @ 1% THD / 2 = 95Wpc short-term
  • Both channels driven into 8-ohm nominal:
    • 89W continuous / 2 = 44.5Wpc sustained.
    • 119W peak (estimated, 8-ohm not measured by ASR) / 2 ≈ 59.5Wpc short-term

(btw. "RMS power" is a misnomer. Power is by definition always the product of RMS voltage and RMS current.)

Background

In the last 10 years, class-D got good. Class-D amplifiers use pulse-width modulation to generate a pulse train output which is then filtered to remove high-frequency pulses. By turning on transistors only as-needed (usually MOSFETs), class-D amplifiers can achieve efficiencies in excess of 90%+. As a result, these amps are smaller, lighter and cheaper to build than their class A & class-AB predecessors.

Block diagram of basic class-D amplifier

The 48V power supply squeezes substantially more performance out of the TPA3255 chipset than the standard 32V PSU. The previous generation TB10D left me wanting more with the standard 32V power, so I am only stocking the 48V V3. These units come with a 24-month warranty. 

Max Power

  • 159W single-channel driven into 4 ohm @ <1% THD
  • 89W single-channel driven into 8 ohm @ <1% THD

Peak Power

  • 300W peak power per channel (momentary) totalling 600W. The 48V PSU is only rated 240W continuous, so this is a short momentary pulse powered by the capacitors in the PSU.
  • 190W peak power per channel (CEA-2006/490A standard) both channels driven into 4 ohm @ <1% THD+N
  • 380W total peak power at <1% distortion, short-term.

Inputs

  • Stereo RCA

Outputs

  • Stereo speaker binding posts or banana plugs
  • Lab Out (minijack / aux) for an active subwoofer. Note that a Lab out is not controlled by the volume knob (Pre-out is a misnomer).

I use the Fosi Audio V3 (48V) amplifier to drive my KEF LS50 Meta's and can easily saturate the KEFs. I also tried the budget Arylic A50+ integrated streamer + and would not recommend it (cold sound, distortion and cuts out at full power.)

You are welcome to bring your speakers for a sound test in Stellenbosch Central.

For more detailed measurements, please see Amir's measurements on AudioScienceReview.

Please refer to the Fosi Audio V3 Product Listing. 

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