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In Reply to: RE: The better the design of the amp and its execution posted by sideliner on November 19, 2024 at 17:23:54:
Could you elaborate a bit on thisOpamps derive feedback from a Voltage divider network which mixes feedback with the incoming signal right at the input of the opamp.
Most audio amplifiers don't do this- instead apply the feedback to the cathode of the input tube, emitter of an input transistor (in the case of more primitive solid state amps) or to the gate or base of a semiconductor that is part of a differential input pair.
In all cases the device to which the feedback is applied is non-linear. So in the process of mixing with the audio signal, the feedback signal is distorted. This causes it to generate higher ordered harmonics and in some cases, IMD.
Resistors of course are a lot more linear.
Norman Crowhurst pointed out this problem 60 some years ago but didn't propose a solution. 15 years later Peter Baxandall also pointed it out but simply proposed 'more feedback' which really didn't work.
In either case if the feedback is wrapped around the amplifier as seen in opamp circuits, it will not be distorted so it can simply do its job.
Edits: 11/20/24 11/20/24 11/20/24
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Follow Ups
- Sure - Ralph 08:28:31 11/20/24 (8)
- RE: Sure - sideliner 18:32:51 11/21/24 (0)
- Sure? - 13th Duke of Wymbourne 11:52:03 11/21/24 (6)
- Yes. - Ralph 13:03:02 11/21/24 (5)
- RE: Yes. - 13th Duke of Wymbourne 10:20:01 11/22/24 (4)
- Yes. - Ralph 10:40:28 11/22/24 (3)
- RE: Yes. - 13th Duke of Wymbourne 17:32:35 11/23/24 (2)
- You can't compare using an opamp - Ralph 09:41:13 11/25/24 (1)
- That's why I suggested we end with the last post - 13th Duke of Wymbourne 14:25:32 11/26/24 (0)
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