good old times
National LF356/LF357 was among populars opamp.
I would like to play with jfets CI for mixer with 47K inputs, filters... Nostalgia !
Even within 80's days, LF353 was not widespread as single opamps. I remember using LF356/LF356A/LF357 and TL072/TL074.
The single was the 351. I almost never used singles in any op amp. It was easier to build with a dual and have a spare on the board - usually I found a way to use it, even if it was just driving an LED. The only real exception was the 311 comparator but that’s not really an op amp.
Game Over!
Ran into "Opamps in Audio circuits – 10 Point guide" by hifisonix, from which I quote:
8. Never use an opamp not characterized for audio usage. Typical examples are uA741 (an early 1970’s relic), TL072 (ok for DC work, but not high quality audio), LF355,356, 357 - also relics from the late 1970’s. Low supply rail, low power op-amps are also generally not good for audio. Look for devices with the following general characteristics:-
Slew rate of at least 10V/us
Full Power bandwidth of 50KHz
Low frequency PSRR of >70dB (modern op-amps do >100dB) on both +ve and –ve rails; HF PSRR should be
better than 70dB
600 Ohm drive capability
600 Ohm 1KHz 10Vpk output distortion of 20ppm or better (modern devices will achieve low single digit ppm
figures at 20KHz and sub 1ppm at 1KHz
Ran into "Opamps in Audio circuits – 10 Point guide" by hifisonix, from which I quote:
8. Never use an opamp not characterized for audio usage. Typical examples are uA741 (an early 1970’s relic), TL072 (ok for DC work, but not high quality audio), LF355,356, 357 - also relics from the late 1970’s. Low supply rail, low power op-amps are also generally not good for audio. Look for devices with the following general characteristics:-
Slew rate of at least 10V/us
Full Power bandwidth of 50KHz
Low frequency PSRR of >70dB (modern op-amps do >100dB) on both +ve and –ve rails; HF PSRR should be
better than 70dB
600 Ohm drive capability
600 Ohm 1KHz 10Vpk output distortion of 20ppm or better (modern devices will achieve low single digit ppm
figures at 20KHz and sub 1ppm at 1KHz
There are some amout of good jfet input op amps, but they are usually double (for example ad823). I can't remembdr single ones (except TL071/081 which are not for audio, but are good for guitar amplifiers because of their distortions).
AD743, AD843?
And look here: jfet input op amps parametric search.
AD743, AD843?
And look here: jfet input op amps parametric search.
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LF357 is a decompensated LF356. Samuel Groner ran the latter through its paces - it had some issues as you might expect from a part this old, but since it runs its output stage much hotter than the TL072, load driving (including capacitive) is far better behaved, approaching NE5532 levels as long as you don't come too close to current limits.
I still can't really think of an application that would literally cry out for a chip like this though. Tape head post-amplifier, after a preamp?
I still can't really think of an application that would literally cry out for a chip like this though. Tape head post-amplifier, after a preamp?
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