DIY ACA mini

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#1,941
Biasing... going OK - following this guy on UT. Now, it's winter here and I keep 18 C in my flat but when summer comes it is cooking and get easily to 25 and I have no cooling - do I dare to use the amp or will it burn? Should I have to re-bias as the seasons shift?

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#1,942
For a resistive load yes. For a reactive load anything is possible.

Here is a response into 6 ohm, 20 ohm and then a simulated full range speaker.

Screenshot 2023-03-23 194606.png


Screenshot 2023-03-23 194631.png



Screenshot 2023-03-23 194723.png
 
#1,943
TNT said:
Now, it's winter here and I keep 18 C in my flat but when summer comes it is cooking and get easily to 25 and I have no cooling - do I dare to use the amp or will it burn? Should I have to re-bias as the seasons shift?
Click to expand...

25C isn't excessive as an ambient temperature to operate consumer electronics at. I would assume it would be fine but you might feel subjectively that the outputs feel very hot.
 
#1,946
TNT said:
Biasing... going OK - following this guy on UT. Now, it's winter here and I keep 18 C in my flat but when summer comes it is cooking and get easily to 25 and I have no cooling - do I dare to use the amp or will it burn? Should I have to re-bias as the seasons shift?
Click to expand...
Well, if you bias at 300-340mv at 18°C, the bias will drift up to about 475-515mv at 25°C if you don't adjust it.
 
#1,956
TNT said:
What about this - valid?

View attachment 1157378

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Click to expand...
This graph won't help since we're looking to maintain a constant bias of 0.3-0.35 V (300-350 mV) for VB and 11.4-11.6 VDC. The y-axis would be the combined resistance of P1/P2 increasing changing with increasing ambient temp, but we're adjusting P1 & P2 in a complicated way to hit our target bias. That would be really, really hard to graph. Once you had it charted, someone will come over, turn off a fan, and then you'll have to make a new graph. 🙂

It's much easier to set the bias and check on it as the seasons change to confirm the bias hasn't drifted too much with ambient temperature. I like your effort. The temperature scale is a nice touch.
 
#1,957
I was the author of that graph. BTW I erred in y axis - it needs to be multiplied by 10.


As I believe I stated in the original post, this graph is not a plot of how Temp changes as you vary bias, but how bias changes with ambient Temp while leaving the pots untouched. This why I included the word Ambient. t I hope that clears up the confusion.
 
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