Line Level BSC Again, adjusting dB.


2008-01-25 4:37 pm
Asked about this a couple weeks ago but have a follow up question.

I know the very basics how passive filters, e.g., as described here, work.

Now, suppose I didn't want 1st order 6db per octave. Suppose I wanted 4db or 3db. I'm not sure how to calculate that. Intuitively if I has a passive low-pass with an R in series and then a C in shunt, I would guess that if I added an R in series with the C shunt so I have an RC shunt, that would reduce the order of the filter. I have no idea how to calculate that though.

You know what would be cool, I've been messing with Duncan Amp Tools PSU Designer II. By messing around with the value and adding and deleting components and then looking at the graph, I learned a lot about how passive filters work in PSUs. (Unfortunately it would let me take out the darn bridge amplifier and also I'd want the graph as frequency response).

I tried a few freeware filter tools around the net and all have just the standard filter topologies defined. It would be nice if there was one where I could add the R/C/L components to the schematic, like PSU Designer, and then give me a frequency response graph. Anyone know of such a freeware?

Right now, this is all mental frobnication on my part to try to learn more about this stuff.