Ron Quan revisited PIM/SID recently with new 3 tone tests, dedicated hardware
John Curl loves pointing to Ron's AES conference paper - but it seems John's not really a detail man as it were, not actually reading the paper, the results tables...
the rest of us keep pointing out to John that in the 1st paper Ron Quan had to use TL06x - the lower power variant of these 3 decade old op amp designs to get any result above his custom measurement hardware noise floor
which points up the trick - look for device where Iq - supply current is measured in microamps instead of milliamps
and really, really don't even think of using something designed in just the last 2 decades, made on isolated/complementary bipolar processes, labeled or promoted "for audio" with few mA per op amp supply currents
John Curl loves pointing to Ron's AES conference paper - but it seems John's not really a detail man as it were, not actually reading the paper, the results tables...
the rest of us keep pointing out to John that in the 1st paper Ron Quan had to use TL06x - the lower power variant of these 3 decade old op amp designs to get any result above his custom measurement hardware noise floor
which points up the trick - look for device where Iq - supply current is measured in microamps instead of milliamps
and really, really don't even think of using something designed in just the last 2 decades, made on isolated/complementary bipolar processes, labeled or promoted "for audio" with few mA per op amp supply currents
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'ere y'go: 3V/MILLIsecond (i.e., 3mV/usec). Unity gain bandwidth is 9kHz, slow enough? 0.45uV current draw. Heatsink not required.
http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP6441
http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP6441
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The LM301 has user adjustable slew rate. Dial it down as low as you want! 1 volt per second is easily possible, just turn the knob.
There are other opamps which offer this same feature but I think you will learn more and become a more accomplished electrical engineer, if you ferret them out yourself.
There are other opamps which offer this same feature but I think you will learn more and become a more accomplished electrical engineer, if you ferret them out yourself.
Slow: uA741 (the classic Op Amp) LM747 (same but dual)
Almost as slow: LM1458 (still widely used)
Slower: LM358 . Class B so for Audio use you must bias it Class A
Slowest yet cherished for a certain *famous* Bass Preamp: LM4250
Idle current is programmable down to very low levels, which makes it popular in active electronics inside string instruments, where a 9V alkaline lasts *years* .
Of course, the lower the current, the lower the slew rate, not a problem for a Bass instrument and to boot, handling less than 1V .
RAT distortion pedals use an externally compensated LM308 , overcompensated for the gain they use, because slew rate limiting sounds smoother/warmer than plain diode clipping.
As you see, all are old timers.
Almost as slow: LM1458 (still widely used)
Slower: LM358 . Class B so for Audio use you must bias it Class A
Slowest yet cherished for a certain *famous* Bass Preamp: LM4250
Idle current is programmable down to very low levels, which makes it popular in active electronics inside string instruments, where a 9V alkaline lasts *years* .
Of course, the lower the current, the lower the slew rate, not a problem for a Bass instrument and to boot, handling less than 1V .
RAT distortion pedals use an externally compensated LM308 , overcompensated for the gain they use, because slew rate limiting sounds smoother/warmer than plain diode clipping.
As you see, all are old timers.
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