[sdiy] inductor source?

[Harry Bissell Jr]

Funny you should drag me out of the woodwork... :^P

You seem to already know the inductors weak points...
succeptability to external magnetic fields... cross
coupling between colsely spaced inductors, change in
value due to proximity of ferrous metals, and
non-linearities with applied signal (hysteresis etc).

All of these could be bugs, or features...

They would (unlike the BBD) be very quiet and their
resonant peaks are not limited to the supply
voltages... od S/N can be very good.

The non-linearities might also add 'character' to the
signals  (who knows... could it be the elusive "phat"
??? :^)

Another problem... try getting LARGE values in small
packages... and when you DO they have a lot of series
resistance... which unlimately limits the Q.

So... smoke 'em if you got 'em.   :^P

H^) harry


--- David Moylan <dave at westphila.net> wrote:

> I've had fixed filters on my mind a lot lately.  I
> built an effect pedal
> format LC filter box a few years ago that could do
> boost or cut at two
> frequencies simultaneously.  Each band had 12
> possibilites.  It was
> essentially passive with make up gain and sounded
> fine but the topology
> limited the effective Q.  That didn't bother me too
> much as I was using
> it primarily for gentle shaping of guitar.
> 
> I used a series LC circuit since in that case the Q
> is dependent on the
> L, so it would remain relatively constant when
> switching between caps.
> And the caps were wired in series around a rotary
> switch.  That's the
> way it's done in Orange amps and it seems to keep
> the pops down.
> 
> It was built with samples I ordered from Wilco. I've
> been fooling around
> with it some more: increased the Q some which I
> liked.  Then, realizing
> I don't use the cut position much I changed the
> topology to only boost.
>  This is more in the fixed filter family since you
> get no signal with
> both knobs down.
> 
> I like it a lot.  I can take a simple saw (with some
> LPF) and go from
> something akin to an upright bass to something that
> sounds like a mouth
> harp or rubber band to insect tones.  Since it seems
> effective and since
> the MOTM fixed filter is a dead project I think, I'd
> like to expand on
> my own little fixed filter.  I figure 3 or 4
> switchable bands would be
> almost as useful as 10 single bands but where can I
> get 1H or larger
> inductors?  Judging from how hesitant Wilco is to
> give me a quote or
> tell me a minimum quantity they don't want to deal
> with small potatoes.
>  It's too bad.  I like these little shielded
> inductors.  Do they have
> distributors?  Are there any alternatives?  Or is
> there enough interest
> to try to get a group buy together?
> 
> Yes, I know resonant filters can be made without
> inductors, but they
> make it so damn easy.  And aren't they more fun?  I
> haven't had any
> problems with hum pickup with these little Wilco BSL
> series.  Hopefully
> Harry doesn't feel about inductors the way he feels
> about BBDs...I can
> hear it now....
> 
> Dave
>