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Hi everyone,

I`ve done a new calibration of the soundcard /loop, since I want to perform some measurements with my new equipment. For that I use the HDMI output of my Macbook Pro and as input a TASCAM122 MKII with a EMC8000 mic. So for calibration purposes, I looped the HDMI output to the input of my AV8003 preamplifier and from pre out (right channel) back into the input of the TASCAM. The result of the calibration measurement is at least disappointing in my opinion (see the graph). It is only within -0.5 and 7.5 dB. Is this normal, or should I chechk for some issues?
When I run a measurement of the loop after calibration, the curve is corrected but it is only within approx. 0.6 dB. That is also not very good, I suppose!? What can be the explanation for this behaviour?

Any help will be appreciated, thanks!

Sven
 

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The loopback is an analog line-level function and can’t be used with HDMI. That probably explains what you’re seeing.

I addition, there’s no good reason to include the AVR in the loopback, unless you’re doing something like trying to determine the bandwidth of its internal EQ filtering.

Review the Help Files - the loopback function is connected and measured only for an outboard interface, like y our TASCAM. However, its response is probably so flat it doesn’t need a calibration file. I have an earlier version of the US-122 and its ruler flat, maybe down a 1/2 dB @ 20 Hz.

Regards,
Wayne


 

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Hello Wayne,

many thanks for your reply. OK that`s clear to me. Then I leave the calibration as is, since I already did a calibration for the Tascam only.

Thanks again,

Sven
 

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The measurement with the AV in the loop looks like it has some processing active (e.g. Dolby PLII or similar).
 
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