|4th October 2017, 10:13 AM||#11|
Join Date: Sep 2017
I want to report my results after studiing the data sheet.
I decided realizing a gain of 20dB and changed the resistors.
Noise is very low, but my max. input level was not enough.
Therefore I changed to 26dB, noise is about half in comparison to beginning and my input level was enough.
From both resistors 39k and 100k I left the 100k and placed a further 39k in parallel to the original. This makes 19.5k, best value in data sheet is 20k with 5% tolerance.
I tuned all my 8 amp boards.
Next step is muting from raspberryPi over GPIO pins and a delayed switched relay in the power supply of the amp boards.
Thank you all for the help and informations!
|5th October 2017, 09:53 AM||#12|
Join Date: May 2016
@papaarrugada Can you please add some illustrations/pictures/schematics with the mods you made?
|8th October 2017, 12:57 PM||#13|
Join Date: Sep 2017
yes, of course.
gain can be selected with two R's.
The table of datasheet shows following selectable values in master mode:
gain | R1 to GND | R2 to GVDD
20dB | 5,6k | OPEN
26dB | 20k | 100k --> I have selected
32dB | 39k | 100k --> default setting
36dB | 47k | 75k
therefore I had to change R1 from 39k to 20k.
I decided to place a second 39k on the top of the default R 39k.
Two 39k R's results in 19,5k, 20k is the suggested value in the table.
But it's in the 5% tolerance (19k to 21k).
I want to add a picture where you can see the "construction".
But I don't know how I can import a pic.
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