Soundcard calibrated

maximm

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Hello everyone! I've just started mastering rew. Which cable to calibrate the sound card as balanced or unbalanced, is there a fundamental difference? Thank you!
 

John Mulcahy

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Not really. If you will be using the input with a balanced source then a balanced cable would be ideal, but there are few applications that require such precision. One of the main benefits of the soundcard calibration is picking up monitoring/feedback loops, either connection is fine for that.
 

maximm

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In the continuation of the topic. I calibre the Focusrite Scarlett 18i6 card, and get a strange spectrum at the output. What's the problem? P.S. loopback trs-trs (2 in - 2 out). The signal level is just as low.
 

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John Mulcahy

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The routing setup is feeding some of the input back to the output, input monitoring must be completely off.
 

maximm

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Everything worked out, thank you!!! But there is another point: how to adjust the signal level: the input channel amplifier and adjust the monitor amplifier or vice versa, adjust the monitor amplifier, and adjust the input amplification of the channel. The measurement results in these cases are different!
 

maximm

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In the first case: input gain - monitor gain
In the second case: monitor gain - input gain. It is not possible to adjust the signal level to -12 dB by any one amplifier because the level is weak
 

John Mulcahy

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Everything worked out, thank you!!! But there is another point: how to adjust the signal level: the input channel amplifier and adjust the monitor amplifier or vice versa, adjust the monitor amplifier, and adjust the input amplification of the channel. The measurement results in these cases are different!
Different how? There shouldn't be any difference in the shape of the response unless a gain setting is pushing the signal into clipping. The SPL at which the response is drawn will change if the input gain is altered without repeating SPL calibration.
 

maximm

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Hi! No, it's not about SPL calibration, I'm interested in the sound card calibration signal level. The first two photos show the calibration signal of the sound card installed only by the monitor pen, in the next two photos the calibration signal is set only by the amplification knob of the microphone input channel. The signal level is completely different. Adjustment to reference -12 dB in the first and second cases gives different calibration results. I wonder which pen to unscrew to the maximum when calibrating the sound card, and which pen to adjust the level to the support one. Thank you!!!
 

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maximm

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Hi! Photo of sound card measurements and measurement files. M1-1 - monitor signal level maximum -26.56, adjustment to -12 with input amplifier of 1 channel. 1-M1 - level of amplifier 1 channel maximum -60.93, adjustment to -12 monitor level
 

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John Mulcahy

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Looks like the input gain has an effect on the input bandwidth, though the differences are small enough not to matter for acoustic measurements with a mic. Fine to continue with mic measurements without a soundcard cal file. If you wanted exact low end precision, connect the mic and adjust the input gain to a setting that gives a sensible input level at the SPL you want to test at (75 dB SPL is fine for room measurements, an input level above -40 dBFS is sufficient). Then for the calibration adjust the monitor level so that the input level is OK without changing the input gain.
 

Theo Aronson

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I just tried measuring/calibrating my UAD Apollo Twin MkII audio interface and got the attached results which seem odd compared to images used in the user manual showing typical interface measurements. Is this measurement below possible or am I doing something wrong?

51897
 

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John Mulcahy

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No, that's just crosstalk from the other channel. It only looks vaguely plausible because of the smoothing applied and the huge SPL axis scale. Looks like you were using the R output channel but measuring the L input channel, so one of those needs to change depending on where you connected the loopback cable.
 

Theo Aronson

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You're right (no surprise). In Preferences for some reason the Audio Output Device defaults to right channel "R" (#2). Is there a reason for this? Once I switched to Left "L" I was able to get proper calibration measurement (attached both as-is and with 1/24th smoothing for reference).

51919
51920

51921
 
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