In planning my audio projects I have studied many op amp data sheets and done much research on the implementation of op amps in audio circuits. I am unsure how to interpret two specifications: settling time and quiescent current.
My research indicates that settling time can be difficult to measure and altered by poor circuit design, but I don't know what the audible effects of a faster or slower settling time are. The op amps I have seen seem to have a range of settling time to .1 per cent error of about 500 nanoseconds to about 1.5 microseconds. Is this a significant enough variation to cause concern? All other factors being equal, is a faster settling time preferable to a slower one? What audible effects could be expected from using a faster settling time op amp versus a slower one?
As to quiescent current, I know that this is the specification that indicates how much current is required to bias the transistors in an op amp, but again, I don't know how or if this affects sound quality. My question is: all other factors being equal, will an op amp with a higher quiescent current operate in a class A output mode to a higher voltage level than a lower one?
Thanks to all who can help.
My research indicates that settling time can be difficult to measure and altered by poor circuit design, but I don't know what the audible effects of a faster or slower settling time are. The op amps I have seen seem to have a range of settling time to .1 per cent error of about 500 nanoseconds to about 1.5 microseconds. Is this a significant enough variation to cause concern? All other factors being equal, is a faster settling time preferable to a slower one? What audible effects could be expected from using a faster settling time op amp versus a slower one?
As to quiescent current, I know that this is the specification that indicates how much current is required to bias the transistors in an op amp, but again, I don't know how or if this affects sound quality. My question is: all other factors being equal, will an op amp with a higher quiescent current operate in a class A output mode to a higher voltage level than a lower one?
Thanks to all who can help.
Settling time is essentially a measure of how the OA behaves in a non-linear mode, ie driven by fast pulses. It is not relevant to "normal" linear amplification mode, so you can safely ignore it for audio.
Quiescent current is the standing supply current (from V+ to V-) befire any load current is considered. The measure you are looking for is output voltage swing for a defined load. E.g +/- 10v at 2K load, giving 5mA available, and still staying in control, ie linear.
Quiescent current is the standing supply current (from V+ to V-) befire any load current is considered. The measure you are looking for is output voltage swing for a defined load. E.g +/- 10v at 2K load, giving 5mA available, and still staying in control, ie linear.
well you can have linear settling time with small enough step - can tell you something about the op amp phase compensation
some very high gain precision op amps have more complicated open loop gain/phase curves from 2 gain stages and may show interesting small signal step response if the closed loop corner frequency is near the open loop excess phase region
for some measurement systems "single pole" response is the only accepted option for fast settling - most settling time literature will be focusing on these sorts of measurement applications
in audio there is little evidence that typical small signal "long" settling tails that aren't accompanied by audible frequency response errors can be heard - and some listening test evidence against
"temporal masking" is a strong psychoacoustic phenomena - we don't hear small features near in time to much larger transients - even for the small signal slightly preceding the big one - but the effect is much larger for the small signal following the big one - the time scales are 100s of us to ms for temporal masking
some very high gain precision op amps have more complicated open loop gain/phase curves from 2 gain stages and may show interesting small signal step response if the closed loop corner frequency is near the open loop excess phase region
for some measurement systems "single pole" response is the only accepted option for fast settling - most settling time literature will be focusing on these sorts of measurement applications
in audio there is little evidence that typical small signal "long" settling tails that aren't accompanied by audible frequency response errors can be heard - and some listening test evidence against
"temporal masking" is a strong psychoacoustic phenomena - we don't hear small features near in time to much larger transients - even for the small signal slightly preceding the big one - but the effect is much larger for the small signal following the big one - the time scales are 100s of us to ms for temporal masking
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