Hoping for ideas here...
I'm using a TASCAM US-1x2HR USB interface for impedance measurement.
I've verified that the Direct Monitor is off, by sending a signal to the line input that I'm using for input and reference, and verifying that it does NOT feed through to the headphone output that I'm using to drive the measurement. Calibration goes fine, including clean-looking sweeps from each of the three calibration steps. But impedance measurements look like the examples of input-to-output feedback, unless I reduce the sweep length to the absolute minimum.
I've verified that the Direct Monitor is off, by sending a signal to the line input that I'm using for input and reference, and verifying that it does NOT feed through to the headphone output that I'm using to drive the measurement. I've also verified that inverting the input (checkbox in Sound Card Preferences) makes no difference.
This is with REW 20.13 under MacOS Ventura. I was running the latest beta but uninstalled and re-installed with release 20.13 in case that was an issue.
Any ideas appreciated!
Captures from cal and testing follow...
Calibration works just fine. Here's the final step with a 45.9 Ohm calibration resistor:
But here's an impedance sweep (96 KHz, 512K sweep length):
Reducing the sweep length to the minimum (REW prompts to increase it) results in a clean measurement. For example, this is at 96 KHz and 256K sweep length:
I'm using a TASCAM US-1x2HR USB interface for impedance measurement.
I've verified that the Direct Monitor is off, by sending a signal to the line input that I'm using for input and reference, and verifying that it does NOT feed through to the headphone output that I'm using to drive the measurement. Calibration goes fine, including clean-looking sweeps from each of the three calibration steps. But impedance measurements look like the examples of input-to-output feedback, unless I reduce the sweep length to the absolute minimum.
I've verified that the Direct Monitor is off, by sending a signal to the line input that I'm using for input and reference, and verifying that it does NOT feed through to the headphone output that I'm using to drive the measurement. I've also verified that inverting the input (checkbox in Sound Card Preferences) makes no difference.
This is with REW 20.13 under MacOS Ventura. I was running the latest beta but uninstalled and re-installed with release 20.13 in case that was an issue.
Any ideas appreciated!
Captures from cal and testing follow...
Calibration works just fine. Here's the final step with a 45.9 Ohm calibration resistor:
But here's an impedance sweep (96 KHz, 512K sweep length):
Reducing the sweep length to the minimum (REW prompts to increase it) results in a clean measurement. For example, this is at 96 KHz and 256K sweep length: