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Chip amp temperatures
Chip amp temperatures
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Old 6th May 2020, 09:32 PM   #1
ggidzinski is offline ggidzinski  United States
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Default Chip amp temperatures

I am building an LM3886 stereo amplifier based on a set of chipamp.com boards that I have had for a few years. It is in prototype mode and I am trying a few different heat sinks. It is amazing how good a $5 IC based amplifier can sound!

1) Can someone give me some experience/guidelines regarding the LM3886 maximum case temperatures at high music volumes? Where do you measure the package? I am currently getting around 60-65C on the exposed package face after extended high volume use using an IR thermometer.

2) Any thoughts on insulated vs non-insulated package? I am currently using the insulated version based on the board instructions claiming that it sounded better.

3) If the thermal limit for the IC kicks in due to overheating does it throttle back gently of does the volume drop instantly?

4) Is there a significant improvement if you go with dual mono vs stereo other than channel separation?

Thanks,

George
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Last edited by ggidzinski; 6th May 2020 at 09:36 PM.
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Old 7th May 2020, 04:38 AM   #2
PRR is offline PRR  United States
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Chip amp temperatures
https://www.ti.com/lit/ds/symlink/lm3886.pdf
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Old 7th May 2020, 07:36 AM   #3
chermann is offline chermann  Austria
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Hi George


As PRR wrote...read the datasheet...


you wrote:
..I am currently getting around 60-65C on the exposed package face after extended high volume use using an IR thermometer.


iīd played around with some ready 3886 boards with the TF chip and without a appropriate heatsink --> 0,64k/W its hard for the chip to handle for a short time some 10W-40W.
pleas take into account that a sine wave from a generator in the lab is lucky not the same load like music playing. music has more pause in between and therefore less energy - so called crest factor





with supply voltage did you use?
higher rail voltage give you more heat in idle mode !...datasheet


have you a oscilloscope to measure your high volume output?
without measurements its just guesstimating


which load did you use?
maybe your speakers are 2ohm or lower...this does not fit to a single 3886 chip
..datasheet


how long was your high volume intermezzo?


chris
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Old 7th May 2020, 02:36 PM   #4
ggidzinski is offline ggidzinski  United States
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My rail voltages are +/- 30V. Using a 1K sine wave and an oscilloscope I can get around 42W output but only temporarily with the smallish heat sinks that I used to start with.

I am familiar with the data sheet. It shows 1 C/W and a max junction temp of 150C so I assume that my max case temp should be 110C or less. I upgraded the heat sink since my initial measurement and I am getting around 70C at sustained high volume music. I have not checked the sine wave again yet. Most of the builds that I see in the gallery use small to moderate heats sinks, what case temps are you guys seeing with music? I am surprised that the theta JC is not higher for the TF package, is that true?

I am now a chip amp fanboy, they sound amazing. I was enjoying my new Tidal streaming trial and my updated music library ripped to FLAC last night using my prototype build and it sounds so good.

George
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Old 7th May 2020, 07:18 PM   #5
chermann is offline chermann  Austria
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Hi George

Actually i am finished with my single LM1875/UTC2050 but no listening test with some 3886 single chip amp boards on my speakers.
I think other members could help here better.
i have just the experience with a 2xTDA7293 pcb (this cheap dual chip board XH-220) that its gets about 55-60į with a 0,65K/W heat sink (14euro %product-title% kaufen)
for both chips. the load was a open baffle 12" sub and W5-2143-so not really low impedance. i have a 18VAC transformer and got about 27V rail
i guess that your impedance is much lower and you ahve 6 Volt overall more .

chris
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