Opinions: On op amp replacement

[jorgen.bergfors at idg.se]

>> I find the greatest reductions in circuit (audio) noise often come from
>> replacing Carbon Comp. resistors with Metal Film. The metal films are
>> usually 1%, which makes summing and diff amps happier at the same time.
>> Also, faster op-amps somtimes do weird things. I built a phase shifter
with
>> quad op amps (LM324) and replaced them with the TL084 (it oscillated at a
>> near ultrasonic frequency). It drove my mother's dog nuts (but she
couldn't
>> hear it). Made me want to not fix it (I hated that Dog...... :-)

>I can confirm that. Phasers are aparently quite sensitive. No HF
>attenuation
>in a chain of all pass filters, opamps driving capacitive loads with
>variable
>resistors in series ...

I use 1% metal film resistors throughout. At my supplier the price difference is marginal. It actually gets cheaper to standardise on one type, as it means half  the quantity to keep in stock (if you buy 100 at a time). Another advantage with the metal film resistors is that they are 0.6W, instead of 0.25W.

/Jorgen