Pixelwarfare
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Fosi Audio TB10D teardown and review
The packaging:
Front:
Back:
Teardown:
TPA3255 chip under the heatsink:
Thermography on dummy loads (4ohm):
Heat issue:
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.
The aluminum heatsink has a reflective surface, making it difficult to measure. I placed a volume knob on top of the fin to absorb the heat, since the volume knob has a black matte surface and is not polished, its emissivity can be picked up by a FLIR imaging device.
Another technique I used was putting 2 drops of distilled water between the heatsink fins. The water has excellent emissivity and will heat up until it boils into vapor, allowing me to accurately measure the temperature until it reaches above 100C or dried up. As you can see in the picture below, the heatsink was extremely hot (85C). Imagine what it would be like if it were enclosed in a sealed enclosure.
Since heat is the number one enemy of all electrical components, cramming all the heat inside the enclosure will not make the components last. For example, the capacitor will have a short lifespan.
If you only listen to music casually, you probably don't need to worry much about the lifespan of the components. However, if you are constantly blasting your ears with loud music, don't expect the components to last for a long time.
Since this issue is widespread and not just limited to one manufacturer, I hope that manufacturers will incorporate some form of active thermal management or improve their enclosure designs to address this problem. Hint: use the casing as a heatsink!
86.6C is the temperature of distilled water trapped between aluminum fins. I didn't have the opportunity to measure the temperature directly above the chip with water because it evaporates rapidly. I assume it was over 100C.
Matt black alu volume knob have much better emissivity to be picked up.
How does it sound?
I conducted a comparison between the Onkyo RZ50 in pure output mode (RCA) and the BT30D Pro (RCA), both using RP5000F towers and an amp selector switch. I was unable to hear any difference between them, which is good news. It appears that the well-implemented TPA3255 chip sounds the same in all cases.
Same 32V-5A adapter used for multiple models.
Everytime I plugged in the male power plug, there were sparks. I can see and hear it.
The power measurement:
Setup:
RCA Input signal @ 1000hz, 1Vrms
Tone control at half way
L & R both driven, 8 ohm load, 50W rms per channel, before clipping. Volume knob at 2.5 o’clock
L & R both driven, 8 ohm load, 60W rms per channel, clipping, Volume knob at 3 o'clock
L & R both driven, 4 ohm load, 85W rms per channel, before clipping. Volume knob at 2.5 o’clock
I wasn't able to reach clipping at 4 ohm load. Either the amp or power adapter goes into OCP protect mode everytime.
Noise was tested at maximum volume. There was a barely audible hiss from the speakers, which could only be heard if you put your ear close to the tweeter. There is no circuit to shut off the signal because it is not audible when sitting away from the speakers.
The TPA3255 chips are efficient and can produce a significant amount of power for their size.. You can increase the power output of these chips by upgrading upto 48V power adapter. However, because on the heat issue, I wouldn't do it unless you modify the enclosure with active cooling.
It appears that many manufacturers using this chip have set their power limits based on the capabilities of the power adapter.
Pros:
Cons:
The packaging:
Front:
Back:
Teardown:
TPA3255 chip under the heatsink:
Thermography on dummy loads (4ohm):
Heat issue:
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.
The aluminum heatsink has a reflective surface, making it difficult to measure. I placed a volume knob on top of the fin to absorb the heat, since the volume knob has a black matte surface and is not polished, its emissivity can be picked up by a FLIR imaging device.
Another technique I used was putting 2 drops of distilled water between the heatsink fins. The water has excellent emissivity and will heat up until it boils into vapor, allowing me to accurately measure the temperature until it reaches above 100C or dried up. As you can see in the picture below, the heatsink was extremely hot (85C). Imagine what it would be like if it were enclosed in a sealed enclosure.
Since heat is the number one enemy of all electrical components, cramming all the heat inside the enclosure will not make the components last. For example, the capacitor will have a short lifespan.
If you only listen to music casually, you probably don't need to worry much about the lifespan of the components. However, if you are constantly blasting your ears with loud music, don't expect the components to last for a long time.
Since this issue is widespread and not just limited to one manufacturer, I hope that manufacturers will incorporate some form of active thermal management or improve their enclosure designs to address this problem. Hint: use the casing as a heatsink!
86.6C is the temperature of distilled water trapped between aluminum fins. I didn't have the opportunity to measure the temperature directly above the chip with water because it evaporates rapidly. I assume it was over 100C.
Matt black alu volume knob have much better emissivity to be picked up.
How does it sound?
I conducted a comparison between the Onkyo RZ50 in pure output mode (RCA) and the BT30D Pro (RCA), both using RP5000F towers and an amp selector switch. I was unable to hear any difference between them, which is good news. It appears that the well-implemented TPA3255 chip sounds the same in all cases.
Same 32V-5A adapter used for multiple models.
Everytime I plugged in the male power plug, there were sparks. I can see and hear it.
The power measurement:
Setup:
RCA Input signal @ 1000hz, 1Vrms
Tone control at half way
L & R both driven, 8 ohm load, 50W rms per channel, before clipping. Volume knob at 2.5 o’clock
L & R both driven, 8 ohm load, 60W rms per channel, clipping, Volume knob at 3 o'clock
L & R both driven, 4 ohm load, 85W rms per channel, before clipping. Volume knob at 2.5 o’clock
I wasn't able to reach clipping at 4 ohm load. Either the amp or power adapter goes into OCP protect mode everytime.
Noise was tested at maximum volume. There was a barely audible hiss from the speakers, which could only be heard if you put your ear close to the tweeter. There is no circuit to shut off the signal because it is not audible when sitting away from the speakers.
The TPA3255 chips are efficient and can produce a significant amount of power for their size.. You can increase the power output of these chips by upgrading upto 48V power adapter. However, because on the heat issue, I wouldn't do it unless you modify the enclosure with active cooling.
It appears that many manufacturers using this chip have set their power limits based on the capabilities of the power adapter.
Pros:
- Great build quality
- Excellent sound quality, to my ear it’s on par with the RZ50 and BT30D Pro
- Low noise floor
- Excellent price / performance ratio
Cons:
- Thermal management
- Sparks
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