I wonder if there is a sweet spot in the LM3886 gain setting and in the optimal input/output voltage that will give the lowest THD?
I've heard setting gain to 20 sounds way better than gain of 10. I'm assuming that is because of lower THD?
I've heard setting gain to 20 sounds way better than gain of 10. I'm assuming that is because of lower THD?
You can see the distortion in the TI data sheet, which recommends a gain of x21 (26.5dB).
https://www.ti.com/lit/ds/symlink/lm3886.pdf
You may want to use this well-designed board, which will have better measurements..
https://neurochrome.com/products/lm3886-done-right
https://www.ti.com/lit/ds/symlink/lm3886.pdf
You may want to use this well-designed board, which will have better measurements..
https://neurochrome.com/products/lm3886-done-right
You will get the lowest THD at the lowest gain supported by the LM3886. That's because that's where you have the largest amount of loop gain available.
The lowest supported gain is 20 dB (10 V/V), but that has undesirable clipping behaviour. The fix is to add Cc across the inputs, Rf2 and Cf2 across the feedback resistor, and increase the gain to 26 dB. That's what's shown in AC Test Circuit #2 in the data sheet. In addition to those components you also need good decoupling. I see you have another thread going on that topic and it seems you're headed in the right direction on that.
Tom
The lowest supported gain is 20 dB (10 V/V), but that has undesirable clipping behaviour. The fix is to add Cc across the inputs, Rf2 and Cf2 across the feedback resistor, and increase the gain to 26 dB. That's what's shown in AC Test Circuit #2 in the data sheet. In addition to those components you also need good decoupling. I see you have another thread going on that topic and it seems you're headed in the right direction on that.
Tom
Correct me if I'm wrong: Not that it is practically possible, but in theory LM3886 will have its lowest distortion if configured as a voltage follower. Is this what a largest amount of loop gain available means?
Tom is saying the lowest stable gain is 20 dB.
The best clipping performance and distortion occur at 26db Gain. In buffer or unity gain the 3886 is a great oscillator.
The best clipping performance and distortion occur at 26db Gain. In buffer or unity gain the 3886 is a great oscillator.