Quote:
Originally Posted by old_tv_nut
You say the scope reading shows a linear range. Do you mean that the voltage is 20% at setting 2, 30% at 3 etc.? (Linear?) Variation should be logarithmic, starting out very small for an increment of say 1 to 2 or 2 to 3, but be relatively huge going from 8 to 9 to 10. If it's a similar size steps from 1 to 2 and 8 to 9, there's a problem with the volume control circuit.
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Ok I just took the scope out again and tried, it is logarithmic, I missed it. Since looking at the schematic the headphone jack is wired to the same STK amplifier IC I used that (and verified before hand that the response was identical), and found that yes it is logarithmic. It's linear up until a point then starts ramping up faster before it clips. But it's linear well past where my speakers are able to comfortably be used. I did say on the video that the headphone jack had an internal load, it's an internal LPAD, I assume to attenuate the headphones so someone doesn't blow their eardrums out.
https://www.youtube.com/watch?v=zISM75LzX9A