Separate In and Out interfaces...possible feature request

dc2bluelight

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Mar 17, 2018
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Possible feature request....

Is there any way to use different interfaces for input and output? This would be useful when profiling interfaces. Like if I want to test cheap DAC and my input device is an audio interface that is of known high performance.

This also implies separate sampling rates, bit depths, and cal files, though just being able to do it at all with the same sampling rates would be useful.

Thanks again for the most fantastic audio test software in the world!
 

John Mulcahy

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Apr 3, 2017
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The input and output devices can be different when using the Java drivers, nothing else is required on macOS or Linux. If using ASIO (required on Windows for more than 16 bit data) a wrapper like FlexASIO would be needed to make the devices appear as a single ASIO device.

To measure the transfer function the input and output need to use the same sample rate. On Windows or macOS it is usually necessary to match the sample rate used in REW in the Windows audio properties default format or Audio Midi Setup respectively.

The RTA can be used to capture information at whatever rate the input device supports to analyse signals from the output device, but those signals would need to come from a different source if they were to run at a different rate. On Windows it is possible to run more than one instance of REW if that option is chosen when running the installer, that would probably be an easier way to run the output and input at different rates when making RTA measurements. You may need to select the same signal type on the generator of the instance running the RTA to get certain analysis results (IMD or TD+N when using dual or multitone signals, for example) so the RTA instance knows what the signal type is.
 

JLM1948

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Jan 12, 2019
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I can testify to that.
With John's help I managed to use various combinations of interfaces, which was useful for determining which is the bottleneck in my quest for a measurement rig that works up to ultrasonics.
At 384 kHz SR, the E1DA Cosmos ADC goes up to about 140kHz, when the Topping E30 DAC fails miserably (-4dB @20kHz!) .
I use FlexASIO as a Wrapper.
Be sure to check the Windows properties of the I/O devices, because they don't follow the Preferences sttings.
 

Clayton Williamson

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May 25, 2017
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I recently found that you can also accomplish this with ASIO4ALL, so REW can access any combination of input and output device that your system can find.
 

Clayton Williamson

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May 25, 2017
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Ahh, I've only been using it at 48kHz where it seems to work well. Wait, what/why the heck are you testing at 384kHz SR?
 

JLM1948

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Jan 12, 2019
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I use it for measurements. When all is said and done I should be capable of measuring frequency response, oscillations and ringing up to 180kHz.
 
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