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Fosi ZA3 Thermal Test After Thermal Paste Upgrade | 4 Ohm vs 8 Ohm Power & Shutdown Results

Fosi ZA3 Thermal Test After Thermal Paste Upgrade | 4 Ohm vs 8 Ohm Power & Shutdown Results

29:15 · Kiss Analog · 1080p · 2026-09-12

In this video I will test the Fosi ZA3 to see how much power it can provide without overheating. I'll test at both 8 ohms and 4 ohms. In this video, I put the Fosi ZA3 Class D amplifier through a detailed thermal stress test after applying new thermal grease to improve heat transfer. This test compares the before and after thermal paste results, including continuous power testing into both 4 ohm and 8 ohm loads. I test the ZA3 at around 100 watts continuous output, monitor case and internal temperatures, check input power, efficiency, THD+N distortion, and observe whether the amplifier goes into thermal shutdown. I also compare behavior with the 48V power supply and briefly test a 32V supply to see if it improves 4 ohm thermal performance. This video also looks at hot spots inside the ZA3, including the TPA3255 amplifier chip area, the heat spreader, resistors, inductors, op amps, and the hot-running NTC inrush thermistor. The ZA3 is compared briefly to the Fosi V3 Mono in terms of heat, efficiency, layout, and thermal behavior. If you’re using the Fosi ZA3 with demanding speakers, low impedance loads, or high power levels, this test should help show what to expect from real-world thermal performance. Let me know in the comments what other Class D, Class AB, or Class A amplifier tests you’d like to see next. Topics covered: • Fosi ZA3 thermal paste upgrade • Fosi ZA3 4 ohm vs 8 ohm testing • 100 watt continuous power thermal stress test • TPA3255 Class D amplifier heat performance • 48V power supply efficiency • 32V power supply comparison • Thermal shutdown testing • THD+N distortion measurements • Internal hot spot thermal camera inspection • Fosi ZA3 vs Fosi V3 Mono thermal behavior This video contains affiliate links. If you purchase through them, I may earn a commission at no extra cost to you: Links and discount codes will be added below if available. My Amazon storefront Link: https://amzn.to/4tj7COH ______________________________________________________________________ Your support is much appreciated;) Patreon - I really do appreciate your support? This support helps me purchase the equipment I use for testing a reviews. Patreon.com/KissAnalog Send your one time donation to PayPal at: KissAnalog@gmail.com ______________________________________________________________________ Fnirsi affiliate link (coupon code: EDDIE6%): https://www.fnirsi.com/eddie_644 Kaiweets provides KissAnalog viewers a discount code: 15% off code: KA15This video contains affiliate links. If you purchase through them, I may earn a commission at no extra cost to you: Links and discount codes will be added below if available. Link to FOSI Audio: https://fosiaudio.com/products/fosi-audio-v3-mono-power-amplifier?sca_ref=5278085.CFVM2I9cAF&utm_source=affiliate&utm_medium=referral&utm_campaign=uppromote Amazon Link to Fosi V3 Mono: https://amzn.to/3SCaudaA Amazon Link to Fosi ZA3: https://amzn.to/4hfiJ8t Amazon Link to Kryonaut Grizzly https://amzn.to/46bjeua 00:00 Fosi ZA3 Thermal Paste Retest Introduction 00:45 Before and After Thermal Grease Test Overview 01:30 Fosi ZA3 vs Fosi V3 Mono Case Size Comparison 02:15 Temperature Probe Setup on TPA3255 Chip Area 03:20 Audio Precision Analyzer and 4 Ohm Load Setup 04:30 Idle Power Consumption and 48V Power Supply Behavior 05:45 Fosi ZA3 100W Test Into 4 Ohms Begins 07:00 4 Ohm Continuous Power Temperature Rise 08:30 Fosi ZA3 Thermal Shutdown at 100 Watts Into 4 Ohms 09:45 Restarting After Thermal Protection Shutdown 10:45 Switching to 8 Ohm Load Testing 11:45 100W Into 8 Ohms With 48V Power Supply 13:00 Power Factor and Input Power Measurements 14:15 Idle Power Draw With Soft Power Switch Off 15:30 8 Ohm Temperature Test Results After One Hour 17:00 THD+N Distortion at 8 Ohms 18:00 Viewer Feedback Request for Future Amplifier Tests 19:00 50W vs 100W Thermal Performance Into 8 Ohms 20:30 8 Ohm Efficiency: 126W Input for 100W Output 22:00 4 Ohm vs 8 Ohm Efficiency Comparison 23:15 Resistor Load Heating Limits During Testing 24:30 Internal Thermal Camera Inspection of Fosi ZA3 26:00 NTC Thermistor Hot Spot and Board Heat Transfer Issue 28:00 Op Amps, Regulators, and Inductors Thermal Check 29:30 Adjusting Internal Wiring Around the NTC Thermistor 31:00 Retesting After Thermal Paste Application 32:30 8 Ohm 100W THD and Waveform Results 34:00 Thermal Camera Shows Resistor Over 100°C 35:30 50W Into 8 Ohms Temperature Results 37:00 100W Into 8 Ohms After Thermal Grease 38:30 Fosi ZA3 4 Ohm Retest After Thermal Paste 40:00 4 Ohm THD, Input Power, and Waveform Measurements 41:30 Thermal Shutdown Still Occurs Around 75°C 42:45 Testing 32V Power Supply With 4 Ohm Load 44:00 Did Thermal Paste Improve the Fosi ZA3? 45:15 Fosi ZA3 Internal Heat Sources Explained 46:30 48V vs 32V Power Supply Recommendations 48:00 Final Thoughts on Fosi ZA3 Thermal Performance 49:00 Future Amplifier Test Ideas and Channel Updates 50:00 Thanks to Patrons, Members, and Subscribers ... https://www.youtube.com/watch?v=S25G

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