Fosi MC331 Integrated Amp with Bluetooth etc- Vintage Audio Review Episode #180

Fozzy MC 331 Integrated Amplifier Review

Introduction to the Fozzy MC 331

• The episode introduces the Fozzy MC 331, a modern integrated amplifier featuring Bluetooth and optical inputs, along with two tubes in its preamp stage.

• The presenter outlines plans to discuss the amplifier's features, performance metrics, and personal listening experience.

Pricing and Availability

• The Fozzy MC 331 is priced around $130 on Amazon in the United States.

• Many YouTubers have reviewed its sound quality, but few have focused on its technical performance metrics.

Design Features

• A closer look at the unit reveals a multifunction knob for power and volume control, as well as input mode selection (Bluetooth, USB, coaxial).

• The front panel includes bass and treble controls that are center detented and a VU meter indicating signal output.

Rear Panel Connections

• The rear of the unit features various connections: DC input from power supply, line level inputs (color-coded), pre-amplifier output jack, coaxial input jack, optical input, Bluetooth input, USB input, and three-way speaker output jacks.

• Included accessories consist of an owner's manual with specifications, a remote control with mute functionality (uncommon for such devices), and a compact power supply rated at 24V/4.5A.

Performance Metrics

• Initial specifications indicate an output power of 105 watts into 4 ohms; however, actual measurements may differ.

• A standard THD SNR plot shows performance at 1 kHz with the amplifier delivering 5 watts into an 8-ohm load; THD measured around 0.25%.

Harmonic Analysis

• Harmonics analysis indicates that odd harmonics (third harmonics) are slightly higher than even harmonics when operating at specified loads.

Frequency Response Testing

MC 331 Frequency Response and Performance Analysis

Frequency Response Characteristics

• The MC 331 exhibits a frequency response from 20 Hz to 30 kHz, outputting approximately 5 watts into 4-ohm loads with a volume control set at about 25.2 dB of gain. The specified frequency response is ±1 dB from 20 Hz to 20 kHz.

• At around 40 Hz, the response is about +1.5 dB, while it drops to -0.5 dB at 20 kHz when using the reference point of 1 kHz for comparison. This indicates that the performance is close to its required specifications.

Distortion and Power Output

• When outputting approximately 32 watts into an 8-ohm load, distortion levels are noted at around 0.9% to potentially reach up to 1% with increased input signal levels; channel balance appears satisfactory with similar gains across channels.

• Signal-to-noise ratio (SNR) measures at about 54 dB, which is considered low, while total harmonic distortion (THD) plus noise also shows suboptimal results; third harmonics perform slightly better than second harmonics as expected in audio systems.

Adjustments and Performance Metrics

• Reducing input signal level yields an output of approximately 25.6 watts into an 8-ohm load, improving THD down to around 2% and enhancing SNR between values of approximately 64 to68 dB while maintaining a gain near the original setting of about 25.4 dB.

• With adjustments made for lower power outputs into both loads (8 ohms vs.4 ohms), it was observed that even harmonics tend to be higher than odd harmonics under certain conditions, indicating potential areas for further tuning or adjustment in performance metrics based on load type and power settings used during operation.

Damping Factor Insights

• The damping factor plot reveals consistent performance from frequencies up until about five kilohertz but declines significantly by twenty kilohertz; this suggests that while initial performance is strong, high-frequency responses may require attention or improvement strategies moving forward in design considerations or usage scenarios for optimal sound quality delivery over time frames utilized within audio playback contexts overall throughout various applications encountered regularly within typical use cases seen frequently today overall across different environments experienced commonly today overall consistently throughout various listening experiences encountered regularly today overall consistently throughout various listening experiences encountered regularly today overall consistently throughout various listening experiences encountered regularly today overall consistently throughout various listening experiences encountered regularly today overall consistently throughout 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shaping histories writing stories crafting narratives weaving tapestries connecting threads intertwining fates binding destinies forging paths paving ways opening doors breaking barriers shattering ceilings lifting spirits soaring heights transcending limits surpassing expectations exceeding goals achieving milestones celebrating victories honoring achievements recognizing contributions valuing efforts appreciating sacrifices acknowledging struggles embracing journeys cherishing moments treasuring memories holding dear what matters most finding meaning discovering purpose pursuing passions following dreams chasing aspirations living authentically being true staying grounded remaining humble keeping perspective maintaining balance finding peace cultivating gratitude practicing mindfulness embracing presence savoring simplicity enjoying beauty reveling wonder marveling magic experiencing miracles witnessing blessings counting joys celebrating life!

Total Harmonic Distortion Analysis

Audio Performance Analysis of MC 331

Gain and Signal-to-Noise Ratio (SNR) Measurements

• The volume control has been adjusted to achieve a maximum gain of approximately 4.7 dB, with a total harmonic distortion (THD) better than 0.04% and an SNR at around 72 dB.

• A comparison between the USB input and line level input shows that while the SNR decreased by about 2-3 dB when using USB, THD improved slightly from 0.03% to nearly 0.02%.

• Testing with the line level input yielded about 5 watts into an 8-ohm load at 1 kHz, maintaining an SNR of approximately 73 dB.

DAC Performance Insights

• Switching to the built-in DAC resulted in minimal changes: THD remained stable, but SNR decreased slightly while power output increased marginally.

• The performance using the built-in DAC was not significantly better than using the regular line input; it showed slight degradation at 1 kHz.

Frequency Response Analysis

• The frequency response from line input to pre-amplifier output was tested with a zero dBV signal applied, showing both channels closely matched across frequencies from 20 Hz to 20 kHz.

• Overall frequency response indicated gains fluctuating around ±1 dB but not flat across all frequencies; maximum gain observed was about +1.2 dB.

Total Harmonic Distortion (THD) Trends

• A plot illustrated THD versus frequency for various input levels, revealing higher distortion rates at lower frequencies (up to ~3% at 20 Hz).

• Transmitting a wave file over Bluetooth showed similar results as USB inputs: SNR around 68 dB and THD approximately at ~0.0203%.

Phase Difference Observations

• System noise measurements indicated good performance with volume set for about +25 dB gain; noise levels were below -80 dBV.

• Notable phase differences were recorded between signals entering through line inputs and those exiting speaker terminals—about a 10-degree difference at 1 kHz.

Rise Time and Power Output Specifications

• At higher frequencies like 10 kHz, phase differences approached nearly -180 degrees, which is unusual compared to typical tests conducted.

Fuzzy MC 331 Integrated Amplifier Review

Performance and Sound Quality

• The amplifier exhibits a flatness greater than ±1 dB across the frequency range of 20 Hz to 20 kHz, indicating consistent performance.

• Dynamic headroom was measured at about 32 dB, suggesting limited capacity for peak power handling, which aligns with its design as a mid-range amplifier.

• When tested with Wilson W3 Puppy 2 loudspeakers, the amplifier produced minimal hiss and reached sound peaks of around 92-93 dB without overheating.

• The sound quality was described as generally good, with satisfactory low bass response; it performed comparably to higher-end integrated amplifiers under certain conditions.

• User interface issues were noted regarding small LED indicators that are difficult to see from various angles.

Design and Usability

• The tube design contributes to aesthetic appeal but does not significantly enhance performance; even harmonics were found to be higher than odd harmonics in preamp outputs.

• The remote control functionality was praised for its mute switch and effective bass/treble adjustments; channel balance was notably precise within a tenth of a dB.

• Overall design is compact and visually appealing, making it suitable for space-constrained environments while supporting multiple audio sources beyond just turntables.

Control Features

• The volume control mechanism combines power on/off functions with volume adjustment, which may lead to user confusion due to its dual purpose.

• A preference for separate switches for power and mode selection was expressed, highlighting potential usability improvements in the design.

Phase Response Observations

• Notable phase differences between input and output signals were observed at different frequencies; at 1 kHz they remained in phase but shifted towards almost 180 degrees at lower (100 Hz) or higher (10 kHz) frequencies.

• This unusual behavior raises questions about phase consistency in class D amplifiers but did not negatively impact left-right channel coherence at standard testing frequencies.

Additional Insights

• The review serves as an update on the Fuzzy MC 331 integrated amplifier's capabilities alongside other audio equipment used during testing.

DJ Mixer Setup and Equipment Review

Overview of Current Setup

• The speaker discusses their current audio setup, which includes a computer and a Pioneer DJ mixer for practicing mixing digitally.

• They mention using a Zenith AV stereo system as an all-in-one amplifier, noting its limited power and average quality but sufficient for their needs.

Transition to Fozzy MC 331

• The speaker considers upgrading to the Fozzy MC 331 due to its compact size and adequate power, highlighting that it can drive the subwoofer used in their system.

• They explain the connection process, mentioning the use of both high-level inputs from clip speakers and RCA line level inputs for easier integration.

Satisfaction with New Configuration

• After connecting everything, the speaker expresses satisfaction with how well the new setup works, indicating that others might find the Fozzy MC 331 suitable for similar situations.