I'm trying to figure out the simplest way to set up a real phase rotator, for integration into a larger mixer that runs on ±15V. Let's assume that 0° to 180° (or -180° to 0°) is all that is necessary, and that a conventional flip can happen outside of the subcircuit. The source is a direct coupled op amp, the output needs to be the same phase.
I haven't simulated this, but I am told that one could make a wide-ish bandwidth 90° version of the signal by cascading amp sections, to crossfade or mix in with the original signal. I think that means at least twelve sections, maybe up to sixteen if you wanted it within .5°. That doesn't seem realistic, for noise floor reasons, even if you used a SOIC quad such as the OPA1604. I've been working with DIP LM4562s, which would translate to both an unrealistic amount of PCB real estate and power supply draw.
I understand that a second-order allpass filter with a dual reverse log control would work to focus the phase crossover at a particular point in the spectrum, but that doesn't quite hit the mark. Radial's Phazer seems to be a more flexible version of this, where they're blending an inverted LPF in with the original signal. It would be tough to cover 20Hz-20kHz otherwise, even with a 100K pot controlling the RC section of an APF.
Obviously the Little Labs IBP is the elephant in the room. I am not seeking to compete, or make a DIY clone, but it is a reference point.
Is there a slick way to simply turn a sine into a cosine, with low noise and something like 25mA drive?
I haven't simulated this, but I am told that one could make a wide-ish bandwidth 90° version of the signal by cascading amp sections, to crossfade or mix in with the original signal. I think that means at least twelve sections, maybe up to sixteen if you wanted it within .5°. That doesn't seem realistic, for noise floor reasons, even if you used a SOIC quad such as the OPA1604. I've been working with DIP LM4562s, which would translate to both an unrealistic amount of PCB real estate and power supply draw.
I understand that a second-order allpass filter with a dual reverse log control would work to focus the phase crossover at a particular point in the spectrum, but that doesn't quite hit the mark. Radial's Phazer seems to be a more flexible version of this, where they're blending an inverted LPF in with the original signal. It would be tough to cover 20Hz-20kHz otherwise, even with a 100K pot controlling the RC section of an APF.
Obviously the Little Labs IBP is the elephant in the room. I am not seeking to compete, or make a DIY clone, but it is a reference point.
Is there a slick way to simply turn a sine into a cosine, with low noise and something like 25mA drive?