Hi Michael,

Buzz Audio of Wellington have a ready-to-go filter board, just what
you need. Take a look here >> http://www.buzzaudio.co.nz/oemprod.htm

The BE74 is what you need. Easier and cheaper IMO to go with one of
these - added bonus, comes with a pre-emphasis network.

Cheers.



--- In LPFM_Radio@..., Michael Hallager <michael@...>
wrote:
>
> Thanks for your reply Stu.
>
> I'm looking at building a 15KHz low pass filter myself (Weighting up
between
> that and a software based solution though these seem to lack a 15kHz
filter)
>
> I'm confused. My research indicates that there are several different
types of
> filters (Chebyshev, Butterworth, Bessel.... ?) and different
'orders' as
> they're called.
>
> What is suited for the purpose and does anyone have a design?
>
> I would like to build an active design based on 741 op amps and a
few passive
> components.
>
> I have already sourced a design off the web but it is a circuit
only, with
> limited information, and specifies values such as 470pF "styr"
capacitors.
> Has anyone ever seen a 470pF Polyester? Because I haven't and the
Jaycar
> catalogue doesn't list anything below 10nF (0.001uF) for any
Polyester type
> capacitor.
> So I have little confidence in this design and the last thing I want
to do is
> spend time and money getting parts to build any questionable design.
>
> What I'm after is something of a known quantity / quality.
>
> Michael Hallager
> net trust ltd
> www.networkstuff.co.nz p.09 839-1000
>