[sdiy] transistor substitution?

[harry]

Sometimes... means either

1: its all you got at the time so what the phuc?

2: you want a special characteristic of that op-amp.  741 for instance...
slow (high frequency oscillation unlikely), stable, robust (lots of output
current
and protected against shorts), symmetrical clipping, no "phase reversal"

(see the archives for phase reversal... its a long story)

Now the TL071 is very fast, quiet, high impedance. A good choice (usually) for
audio...

Now in this case... "usually" is synonymous with "sometimes:...  (here we go
again)

H^) harry

Mountain Man wrote:

> I'm wondering if the "sometimes" means "occasionally" or "under some
> conditions"?  If it's door #2, a bit about how to choose would be helpful.
> Oh, and thanks for sharing this, Tom, I know it's going to keep me sane :)
>
> Elby
>
> "tomg at efm" wrote:
>
> > It's not a big list, so far everything I've tried works
> > with these substitutions and from this list most special
> > function devices can be built.
> >
> > small npn - 2N3904
> > small pnp - 2N3906
> > med npn - TIP29
> > med pnp - TIP30
> > large npn - 2N3055
> > large pnp - 2N2955
> > npn-pair - 2SC1583
> > pnp-pair - 2SA978
> > n-fet - 2N3819
> > p-fet - 2N5461
> > high speed n-fet switch - J112 (2N4392)
> > signal diode - 1N4148 (1N914)
> > single opamps - TL071 ( sometimes a LM741)
> > duals - TLO72 ( sometimes a LM1458)
> > quads - TL074  ( sometimes a LM324 )
> >
> > The 123 is a small gp npn - 3904
> >
> > Tom
> >
> > > This is such a recurring question...  And although
> > > I have no answer for this directly, I think it
> > > begs a better solution than for people to keep
> > > having to dig around for the answers.
> > >
> > > I have several megs of free webspace.  I would be
> > > happy to put up a simple page which lists parts
> > > and subs.  If any of you have the time, please
> > > send me (privately) parts substitution info and
> > > I'll put it up.  This will be a SIMPLE type
> > > of page with a line item for each part with
> > > it's cross reference to suitable subs.  The
> > > site I will use has no banner ads or popup
> > > windows.
> > >
> > > I also think that we REALLY need an FAQ, but that's
> > > another issue.
> > >
> > > If there is no interest in doing this, I'll know by
> > > the lack of emails about it.
> > >
> > > "Thom Somneevich" <thom_s4 at hotmail.com> wrote:
> > > >Hello all,
> > > >I'm gathering the parts for the EMS filter; does anyone know of a
> > substitute
> > > >for the bc109c transistor other than the nte123a (which is what Mouser
> > calls
> > > >up when I search for the former)? The nte123 is $1.50 a pop, which I'll
> > pony
> > > >up if I have to, but... you understand.
> > > >Thanks,
> > > >thom
> > > >_________________________________________________________________
> > > >Get your FREE download of MSN Explorer at http://explorer.msn.com
> > > >
> > > >
> > >
> > > -- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
> > > -- Linux Rex         | RedWebMail by RedStarWare
> > > -- FatMan: www.teklab.com/~chordman
> > > -- NonFatMan: members.xoom.com/_XMCM/chordman/index.html
> > >
> > >