resistors: 5% vs 1% etc ?

[Harry Bissell]

1. are all 5%, 1/4 watt resistors made (relatively) equal? i.e, will the 
ones i buy at rat shack give pretty much the same performance as
mouser's?

I buy resistors from Digi-Key, I get the 1%, 1/4 Watt, 50ppm tempco
resistors for $8.00 for 200.  Start with the most common values like 1K,
10K, 100K, 49.9K (use in place of 47K 5%)... pretty soon you have a
collection. Get one of those fishing tackle boxes with the little
compartments and load 'er up.

(don't confuse the 50ppm with the "tempco" resistors we talk about for
compensation, they are +3500 ppm usually. These tempcos are just very
small... the resistors are temperature stable.)

2. when should one use 5% resistors and when 1% ?

Use 5% when you don't give a shit... I use a 5% for a pull up resistor
on a logic gate, if the app. doesn't care about value (like 470 ohm is
good but 1K is fine also) and if I don't care about noise (so what the
digital gate needs 2.5 volts of noise to trigger...) then I use 5%.

Use 1% these days. There is no cost savings in 5% parts anymore...

3. what's all this metal-film, carbon-film business anyway?

Metal Film resistors are usually quieter and more temp stable than
Carbon Film and superior in most uses. Some very high values like 10Meg
might be better in carbon film.

Both metal film and carbon film may have a slight (but real) amount of
inductance. This can be a problem in RF but is usually unnoticible in
all audio circuits. In these cases the now rare Carbon Composition or
the new Bulk Cermet, or silicon carbide resistors are useful. You will
probably never need these types. (I do)

my applications are simple audio projects (like TomG's circuits) but i
want 
to use the best parts i can!! :)

The bset advice I have is to use the 1% resistors, the appropriate types
of capacitors... and read in the app notes of my capacitor primer about
decoupling. Add lots of decoupling caps. I put them on every chip !!! 

:^) Harry
thank you!
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