In this link (below) Nelson Pass suggests a method to throw away some gain when operating an op amp at low and unity gains.
http://www.diyaudio.com/forums/solid-state/6558-opamp-inverting-input-sounds-better.html#post67880
I understand the principle but can't come up with a schematic for the method he suggests:
"If the circuit has less than 20 dB gain, I toss some away.
With an inverting amp, a resistor from the - input to ground
will do it. If not, then resistance from both + and - to
ground is used."
My best shot at the inverting configuration is shown below.
For the non-inverting config i can't come with anything that isn't simply throwing away input or changing the gain in the feedback loop.
I am interested in trying this out with an amp i am building that is based on Juma's schematic which is a version of the GC SuperSymmetry also proposed by Nelson. Juma's schematic can be seen here with opamp input buffer:
http://www.diyaudio.com/forums/pass-labs/36398-gc-supersymmetry-23.html#post1710811
and here with B1 style input buffer:
http://www.diyaudio.com/forums/pass-labs/36398-gc-supersymmetry-23.html#post1995610
I plan on using a LME49710 which has 140dB of open loop gain as the input buffer and am preparing for the possibility that it may be near oscillation at unity.
The alternative approach i am considering is having less gain around the opa1632 and adding gain to the LME49710. Even if i go this way i would still like to better understand Nelson's idea.
Thanks for helping.
http://www.diyaudio.com/forums/solid-state/6558-opamp-inverting-input-sounds-better.html#post67880
I understand the principle but can't come up with a schematic for the method he suggests:
"If the circuit has less than 20 dB gain, I toss some away.
With an inverting amp, a resistor from the - input to ground
will do it. If not, then resistance from both + and - to
ground is used."
My best shot at the inverting configuration is shown below.
For the non-inverting config i can't come with anything that isn't simply throwing away input or changing the gain in the feedback loop.
I am interested in trying this out with an amp i am building that is based on Juma's schematic which is a version of the GC SuperSymmetry also proposed by Nelson. Juma's schematic can be seen here with opamp input buffer:
http://www.diyaudio.com/forums/pass-labs/36398-gc-supersymmetry-23.html#post1710811
and here with B1 style input buffer:
http://www.diyaudio.com/forums/pass-labs/36398-gc-supersymmetry-23.html#post1995610
I plan on using a LME49710 which has 140dB of open loop gain as the input buffer and am preparing for the possibility that it may be near oscillation at unity.
The alternative approach i am considering is having less gain around the opa1632 and adding gain to the LME49710. Even if i go this way i would still like to better understand Nelson's idea.
Thanks for helping.
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Nelson, thanks for the confirmation on the inverting configuration as well as increasing this threads view count by almost 3X.
Does anyone want to take a shot at the non-inverting configuration. I can't seem to do it without changing the gain or throwing away input.
Merry Christmas
Does anyone want to take a shot at the non-inverting configuration. I can't seem to do it without changing the gain or throwing away input.
Merry Christmas
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