Is there any other way to filter the power supply? Plus other questions

[Rob Strand]

read it's a capacitance multiplier, right

Some people call it that but it's not technically correct.  It enables the filter to draw more current, so for the same amount of filtering you can use a larger resistor and a smaller cap than a direct RC filter.   It can't really store charge like a large cap.

Hmmm, looks like the simple RC is good enough.

In many cases it turns out that way.   The active filters can give less voltage drop at higher currents.  The active filter avoids large caps and in some cases avoids electrolytic caps altogether.

The active filter has a built in loss of 0.7V whereas the RC filter has a drop depending on the resistance.  With the values I've given on the active filter the a 5mA load has roughly 760mV drop which is the same overall drop as 760mV/5mA = 150 ohm resistor.    At 10mA the active filter has roughly 840mV drop which is the same overall drop as a 840mV/10mA = 84 ohm resistor.

So as the load current increases the RC filter needs a smaller and smaller resistor for the same voltage drop as the active filter.   That means the filtering for RC filter will get worse unless you start using large caps.

For the active filters I've shown with 47uF an RC filter would need about 220uF + 1k to get the same filtering which means the voltage drop of the active filter will be lower for currents over about 0.7mA.    In other words the RC filter would need too much voltage drop to get that level of filtering.

Where the active filter cannot compete is when you want less than 0.7V drop.   With an RC filter you can use a small resistor and put up with less filtering.

[mark2]

I have some insight into the 1Spot

Sorry if this is common knowledge already, but did you design that? I've seen or heard your name alongside Truetone that made me think you work there. (on an Ask Zac episode?)

[R.G.]

I work for Truetone. I did not personally design the 1Spot - it pre-dates me at the company (Visual Sound, as it was then; name changed). I do the occasional look into any issues that come up.
I am impressed with the abilities of the guy who did design it.