[sdiy] Fixed filter bank questions

[Tom Wiltshire]

> On 8 May 2019, at 22:04, David G Dixon <dixon at mail.ubc.ca> wrote:
> 
> FIRST QUESTION:  Is there anything wrong with any of these concepts?

Nope.

I’d just flag up that Rod Elliott of the ESP audio pages makes a good argument that the use of 1000Hz as the “centre” of audio is misplaced. Instead, he goes for 640Hz as the geometric centre based on a ten octave range from 20Hz to 20.48KHz:

http://sound.whsites.net/dwopa2.htm

Having experimented with this, I’ve found that I agree with him. It makes a good “mid” frequency. Consider it.


> SECOND QUESTION:  Is there something fundamentally less desirable about doing it my way than doing it Yves’ way?

I don’t think so. I’d have done it your way too, for the same reasons. It seems sensible to reduce the number of expensive caps (these are good quality close tolerance film caps you’re using for something like this, right?!) and use resistors to set the frequency.
Personally, I wouldn’t fret too much about getting the resistor values absolutely spot-on, unless you’re going to buy 1% tolerance caps too. If the caps are 5%, there’s not much point stressing to find an exact resistor value from the E192 series…

 
HTH,
Tom