early 70's-80's monolithic op amps were compromised by not being able to use equally good npn and pnp transistors or jfets together
by the 90's complementary symmetry processes became available
in the late 90's thru to today there has been an explosion in demand for higher performance op amps and huge investment in research, design, and semiconductor manufacturing processes for high performance analog signal processing
early monolithic op amps were easily beaten in performance by better discrete op amp modules of the day - the JE990 is the classic discrete op amp for audio
now days individual designers using catalog discrete parts can't do that much better than the JE990 - but today's monolithic op amp designers have unprecidented control over transistor parameters, matching and use thin film high accuracy resistor on the chip - they have better modeling, design tools, experience and institutional knowlege than any lone wolf designer
and they have applied those advantages competing for market share in telecomm A/DSL drivers that are perfect for dynamic headphone amps
medical ultrasound demands low noise, distortion and high bandwidth too - modern monolithics far outperform any discrete op amp at audio frequencies for anything except moving coil phonograph cartridge preamps or high Voltage output
that doesn't mean you can easily buy the best of today's monolithic op amps in a great headphone amp - exactly because of the deep rooted market predjudices that cause most to dismiss "op amp" audio
another bad meme here is that amplifiers should be chosen to "tune" your sound - logically all "good enough" (for all errors to be inaudible) amps of any technology Should "sound" the same - series impedance can be added to SS amps to tune their response to more closely resemble tube amplifiers - but it doesn't increase the amp's technical accuracy
Edited by jcx - 5/28/11 at 5:19am