Gain setting components in schematic...

[Externet]

Good day.
The data sheet for a class D audio amplifier IC HT6872 does not show the formula for its single-ended two-gain-setting resistors Rin, shown below as both being 12KΩ. Any educated guess to set it ? Speaker Z=4Ω; input is from electret microphone or higher levels.
The lower the Rin resistance; the higher the gain ? Limits ?
For an unbalanced input; can pin 3 be just grounded ? Would such change gain ?

 

[FvM]

If you can supply an English data sheet, we might be able to help.

 

[Externet]

Thanks. Now I know what happened. Found a data sheet in English weeks ago; printed it and contained only 3 pages. Searching today again, shows the chinese document being 12+ pages. So the gain information may be at those missing pages .

Av=200/Rin ??? 200/12K = 0.016 ???

Chinese data at ---> https://html.alldatasheet.net/html-pdf/1143414/YONGFUKANG/HT6872/4223/6/HT6872.html (Page 6)

 

[dick_freebird]

It looks like the front end is a fully differential op amp or something
like it. If the vendor recommends Rin as the gain setting "handle"
then you probably could figure out the internal Rfb value by what's
advertised for the 12K Rin case, and then you can figure others
knowing Rfb.

 

[betwixt]

"Google Translate" goes a pretty good job of translating to English. Try downloading the Chinese data sheet and passing it to GT, it won't translate text in images but everything else is done very well. You can download the translated document with "-1" suffix added to its name.

Brian.