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发表于 2019-9-22 10:40
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我在diyaudio.com网站也发了这个贴,一位加拿大的烧友看了我的电路图,给我了如下建议,他提到可以像天龙的自动控制偏流技术,开机时用大偏流,温度达到工作稳定温度后再切换为正常工作偏流,可以使功放尤其是A类功放开机后,迅速达到稳定状态,这个建议很好,我之前还没想到,我这次就在AVR CPU固件程序里加上这个功能。
You should follow palstanturhin advice. This is how it was done by Denon in the 90’s for automatic bias and the main advantage that Denon claimed was that the circuit was set to reach more quickly the optimal bias after power up thus stabilized output transistors temperature. Based on your chassis and only about 20wrms in 4 ohms max I suppose that you will have a high bias in class A this takes a longer time to stabilize. Your solution with a cpu allows to change your target bias to start with a higher one after amp power up and then reduce it until temperature stabilization.
In your case you do not adjust against temperature and that is the flaw in your circuit since you monitor only the input voltage of the mosfet. Also, with 3 relays you only have a max of 8 voltage settings. With an opto you can adjust any required voltage level.
One additional note is that you should have a cap for frequency stability margin and from what I remembered we had installed it in the feedback loop....
Fab
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