[Don Pearce[_3_]]

On 12 Feb 2013 16:21:36 -0500, (Scott Dorsey) wrote:

Don Pearce wrote:
On 12 Feb 2013 15:55:35 -0500, (Scott Dorsey) wrote:
Arny Krueger wrote:

Bottom line - slew rate has to be rediculously low to be audible with
real-world music. The exagerrated reports about the audibility of slew rate
limiting from the late 1970s were due reliance on sighted evaluations which
we now know to be invalid for determining the audibility of subtle
differences.

Strange, I thought they were due to power amplifiers from major manufacturers
with slew rates only around 0.1V/microsecond. (At least two of these vendors
were also noted for amplifiers that burst into flame, as well, so clearly
stability concerns were not addressed well.)

After folks learned to stop using TV horizontal sweep transistors for audio
output stages, and working engineers learned that not all amplifier distortion
issues can be solved by adding more feedback, things got much better.

Slew rate limiting doesn't happen in the power stage. It is due to the
input stage's inability to source and sink enough current to charge
and discharge the dominant pole cap around the voltage amplifier
stage. It current-limits on large HF signals. You can generally fix it
by increasing the emitter current in the long tail pair and decreasing
the dominant pole cap.

This is true. Sorry for my not being clear and piling a number of different
amplifier problems of the seventies together in one category.
--scott

And there ere plenty of problems. It wasn't until we had the serious
circuit analyses courtesy of folks like Doug Self that all of the
problems found solutions.

d