![]() Spending $10-$20 for a low noise high voltage opamp won't help if the circuit setup has hum and noise on its own. That last is a caution for even the super-duper opamps. The difference from the jellybean TL072 to the 833 or 5532 is not huge, and may not be audible depending on how well the circuit is set up to be low noise. The NE5532 has a much lower input impedance that is generally known, about 100K. The TL072 is pretty darn quiet unless you have a bad one or a circuit which lets it amplify circuit noise. There are rail-to-rail input and output opamps, but they tend to be expensive and also have lower maximum power supplies. The outputs of opamps can't go beyond the power supplies either, and most general purpose amps only go to within a volt or two of the power supplies, similar to the inputs. The only way you get bigger than that is with rail-ro-rail input opamps, and those give you the extra few volts to the power supply, so with +/- 18V power you'd get +/- 9V peak inputs. However, the TL072 and most other general purpose opamps can take +/-15V to +/-18V power supplies, so this makes the input range as big as +/-7V (14V total). ![]() This is true for most general purpose opamps. The linear range of the inputs is generally a volt or two lower than the highest power supply voltage and a volt or two higher than the lowest power supply voltage. A lot of how big a signal it can handle depends on the size of the power supply.
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