Im trying to finalize a few last tings on my custom board here.. to tweak the audio (volume and filter/range) a bit better..
I got some time to dial in the pots for both the volume and the ‘filter’…. and got some odd results...
summary: (fine tuning resistors for volume level (R5/R6) and audio filter/range (R8) for final pcb placement/production)
schematic (for those that need it)
quick image to show how I wired it up... (similar for R8 too..but only used one side of pot of course)
I soldered wires from the 3 resistors (2 wires from filter resistor (R8) pads) & (3 wires from resistors (R5 & R6) pads)
I put a 1K pot on 8R (filter) & a 100K pot on the R5/R6 (volume).. adjusted both until it ‘felt’ good to the ears in both good volume, but not too much as to distort,..and a good range of lows & highs, but not where it cracked or hissed..
I metered the pots..(set @ 200k o meter)
R8 (filter) resistor: was about .98 (980 ohms) is how I read it
R5/R6 (volume) resistor was:
R5: 91.0 (91k ohm)
R6: 4.9 (4.9k ohm)
Dug through my boxes.. and (still using the breadboard) I replaced the pot with:
R8 = 1k ohm
R5 = 100k ohm
R6 = 4.7k ohm
And it still sounded good/great…
So I took my a finished board.. and used the SAME values.. but in SMD footprint for the board.. and it sounds DIFFERENT..
Volume seems to be ‘ok’ still.. but the ‘filter/range’ seems to be a bit muffled? A clear difference than on the breadboard?
I have the two board still set-up, one is my ‘dev/practice’ board to do changes to.. and is connected to breadboard as well for prototyping with this board…
The other is standalone like normal.. but I replaced those resistors with values above..and as per my results from the dev board/breadboard tests..
What am I missing? Doing wrong here? How can they sound different, yet use the same values?