Continuing from my recent post: To eliminate noise and distortion in my audio circuit, I am convinced the solution boils down to two things, head room and ground current. I am extremely leary of audio noise associated with power grounds. Why? Because I manufacture guitar pedals that must be connected to amplifiers and other effect devices. All these "other" devices have different ground potentials. I have had more success with noise not using the power ground, and creating a separate audio virtural ground. I have used Ti's TLE2426 over a number of years with success. The problem with the TLE2426 has always been the limit of 20mA. With my current circuit experiment, powered with a simple 9 volt DC regulated power supply, the current draw on the power supply is 14.73mA. This current is well under the 20mA limit of the TLE2426. Still yet, I have the feeling that it is not a "good enough" virtural ground for two reasons. I am assuming the limited grounding is limiting the head room of the power rails, as I am feeding a OPA134 pre amp to a SSM2018 VCA, and controlling the VCA with a infrared photo transistor. Because of limited head room I am getting distortion when the system is driven. It is also difficult to adjust the infrared sensor that controls the VCA and I have a feeling it is all because of a poor virtural ground. I installed a 4.7uf capacitor across the rails of the TLE2426 and it helped with the distortion. I knew at the time I would probably need more than the 4.7uf capacitor and will try a larger capacitor today. Of course the obvious thing to try would be to buffer the TLE2426. I do not have any current buffer op amps available, so I am going to try a OPA134 arranged with feedback and gain. I noticed the OPA134 has a current rating of 35mA, so I am hoping this gives me a better ground. If anyone has any suggestions on a better ground I would like the information. I do not want some complex virtural ground that requires a bunch of parts and filtering. As for head room, I do understand that more voltage on the rails will solve head room proablems--"IF"--the virtural ground can handle the extra power. I would like information on Ti's miniature isolated DC/DC converters where I do not have to use the miniature DC/DC converter's ground. WHY--because of the fear of power supply white noise. Even when the frequency of these power supplies is far above the audio range it still shows up as reflected noise. That is why I am not buying into the term GALVANIC ISOLATION. Maybe I can be proven wrong. Any help you can offer will be appreciated. Thanks.
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