[sdiy] filters, inductors & Q

[René Schmitz]

Hi all,

I just wanted to add, that you shouldn't overlook the possibility of 
winding your own coils. There are ferrite materials  (torroid cores) 
that allow coils in the mH range with moderate wire gauges i.e. thick 
enough to handle, and winding numbers , i.e. not requireing 1000s of 
windings. Torroids also have the advantage of being more insensitive to 
external fields.

Cheers,
  René



JH. wrote:
>>The good reason 'not to', is the expense & the size and the weight
>>and the comparative unobtainability.
> 
> 
> Toko inductors are quite affordable and available, and Gyraf use them to
> build
> passive (with tube makeup gain) equalizers.
> 
> I plan to build something like this in the near future as well.
> 
> Can't say much about pro's and con's yet - I'll try and listen and see if
> I'll like it.
> 
> Generally, it's easy to get fairly good inductors in the mH range, up to
> 100mH.
> This means you need low impedance circuits (600 Ohm ...) to make good use
> of them in midrange filters. If you want to go low frequency, or high
> impedance,
> you need more Henries, and that normally means specialzed inductors that
> have their price. See www.sowter.co.uk for instance.
> 
> I have a Neve input channel clone here on breadboard, and themain things
> missing
> are a multitapped inductor for mid equalizing, and the output transformer.
> 
> Back to the Toko's, apart from running low impedance it would be good to run
> them
> low level, too, in order not to overdrive them. This might (might! -
> actually I don't know yet)
> problems with hum from mains trafos, so what I plan is putting a handful of
> Toko's
> into a small  mu metal enclosure, pot it up with epoxy, and use that as an
> inexpensive
> multi-tapped inductor such as you need them for passive equalizers.
> 
> 10k : 600R input transformer, passive EQ, and then a tube amp for gain
> recovery
> looks like a fun project!
> 
> JH.
> 
> 

-- 
uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159