I have a Qu-24. Searching the forum I see that 0dB on the meters on the Qu-24 equates to -18dBFS in my DAW (digital). I’m trying to calibrate some levels. If I am sending a -18dBFS 1kHz tone via USB to the Qu-24 should I expect it to be at 0dB on the Qu-24 or -36dB?
For Analog Line Level signals. I’d like to send a line level signal from the monitor out on another interface. If I use a 1kHz sine wave at -18dBFS (digital) should I set the gain on the input channel on the Qu-24 so that it is at 0dB?
I’m just a bit confused on the best way to calibrate each device. Should I use a multimeter and check the RMS level of the analog signal going in to the Qu-24? And what voltage should it be?
Thanks
0dB.
Digital domain, it is not related to analog domain unless it is converted. The specs of the converter define what happens in the analog domain.
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May I ask how you arrived at the conclusion that you should expect exactly -36 dB as an alternative?
Keep in mind that the meters on your input channel only display the value after the trimmer and signal processing chain, so everything there must be zeroed out or deactivated to show the incoming input level.
Or, to put it differently than my predecessor: With a digital USB input, you have no analog gain available at all (- at most, the trimmer, which in this case must of course be 0 dB).
If you can use a good measuring device that can actually measure RMS, the analog 0 dB (+4 dBu) value should be 1.228 volts.
Thank you both for the replies.
I posted this question in a fit of frustration. The reason being I was not getting the expected levels coming from another device and it turns out the device is faulty. This made me question what I thought I understood. You have both confirmed my understanding was correct.
Knowing that 0 dB should measure 1.228 volts is useful information though so thank you. That is a reference I can use in the future.
I came up with -36dB from the values I was seeing on the Qu-24. I was generating a -18dBFS (digital) test signal and sending it from the monitor out on my external device and the Qu was showing a much lower value on one of the line inputs. Knowing that over USB there is a 18dB difference I was confusing analog vs digital inputs and questioning my own math skills. Never overestimate your own cognitive skills.
Nice that you were able to clarify the issue with the defective device and also how you describe it here in conclusion.