QU USB streaming -- levels seem low?

Qu Qu General Discussions
1

I bought a QU-16 recently and did my first serious recording with it today. I’m using it with Digital Performer 9 on a Macbook Pro.

I’m puzzled by what appears to be about a 6 dB discrepancy between the QU-16’s internal metering and what DP’s meters are telling me.

I generally try to set levels so that peaks are between -12 and -9 dBFS. Average levels will depend on source dynamic range, but for most pop sources they’ll tend to be in the -24 to -18 range. Assuming that -18 dBFS = 0 dBU, which I think is the standard these days, that means if I’m getting my preferred levels on the DP meters, I should be seeing peaks between +6 and +9 and average levels between -6 and 0 on the QU-16’s meters. Instead I’m seeing levels at least 6dB higher than that, and I’m frequently seeing the QU-16’s input channel peak LEDs firing even though the levels on the DP meters are never noticeably higher than -9 dBFS.

Can anyone explain what’s going on here? Are the QU meters just ultra-conservative, or am I actually coming close to overdriving the QU’s analog circuits at these input levels? And if it’s the latter, why is there this mysterious attenuation happening between the input metering and Core Audio?

2

I’m sure the A&H people can address the specifics of the levels but in general most gear runs as 0dBU as the norm and +3 as peak while A&H runs +6 with +10 as peak.
I could be wrong but that is what I observed.
I haven’t done a lot of recording on my QU yet so I can’t speak to the USB audio levels, but I will look into it.

3

QU meters are the max of various points through the audio chain. So it depends what you have inserted into the chain, and where your tap point is…

4

Not true Bob, only the Peak LED is multipoint.

Input meters are post processing, pre fader. Mix meters are post fader. Where there is no individual L/R meter, stereo channels will display the hotter of the left or right channel.

Yes, 0dB on the meters is -18dBFS in the DSP.

DC

5

You can adjust the levels you’re sending to the computer.
See page 38 of the manual:

“Adjust the channel Direct Output Trim from off to +10dB gain. The default setting is 0dB.
These are global settings affecting all channels.”

6

Hi all, as Mark says, use the Direct Output Trim, and a bit more input level.
The recording level is taken at -18dBFS to allow for sufficient headroom before clipping from the output signal to the converters, however the Direct Out Trim can be used to boost this level by up to +10dB and you can easily push levels to +12dBu in metering before clipping. Some balance between input gain, mix level and direct out trim can compensate for this if you wish to avoid normalising the signal through audio software.
Thanks. Harry.

7

Doh, of course it is only the peak that’s multipoint… oops