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Author Topic: Audio Interface (USB Pre2) "flatness"  (Read 820 times)

Erik Jerde

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Re: Audio Interface (USB Pre2) "flatness"
« Reply #10 on: March 15, 2019, 02:05:44 pm »

QSC got back to me today.  Here's what they had to say:

We have confirmed a difference in the phase response of the 110f inputs vs. the phase response of other QSC input circuits such as the CIML4 card.  Keep in mind the 110f was conceived to be used in the meeting room environment rather than the performance audio space.  One requirement of that space is a smaller form factor, and we believe this is a result of the miniaturization of the input circuitry.
 
Note the measured phase shift only applies to 110f analog inputs, so this will not occur on any sources brought in through the network, SIP, USB, etc.  If you have applications where you feel this phase response is unacceptable, you could use the analog inputs of a CXDQ amplifier or IO Frame in conjunction with a core 110f, or move to a core model with the CIML4 card such as the Core 510i.

I need to grab a BSS Blu-100 and measure it now to see if it has similar issues.
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Mark Wilkinson

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Re: Audio Interface (USB Pre2) "flatness"
« Reply #11 on: March 19, 2019, 02:41:39 pm »

QSC got back to me today.  Here's what they had to say:

We have confirmed a difference in the phase response of the 110f inputs vs. the phase response of other QSC input circuits such as the CIML4 card.  Keep in mind the 110f was conceived to be used in the meeting room environment rather than the performance audio space.  One requirement of that space is a smaller form factor, and we believe this is a result of the miniaturization of the input circuitry.
 
Note the measured phase shift only applies to 110f analog inputs, so this will not occur on any sources brought in through the network, SIP, USB, etc.  If you have applications where you feel this phase response is unacceptable, you could use the analog inputs of a CXDQ amplifier or IO Frame in conjunction with a core 110f, or move to a core model with the CIML4 card such as the Core 510i.

I need to grab a BSS Blu-100 and measure it now to see if it has similar issues.

Thanks for that. 
Below is a CXDQ input straight to a core110f output at 96k, as suggested by QSC.
Versus the analog core input like we were previously posting; I'd call the low freq end definitely flatter, and the high end less squirrel-y.
It's not the super smooth traces we usually see from a pure speaker management processor, but certainly more than acceptable IMO.

As far as the high end phase tail wagging either up or down with a one sample delay change, I was able to confirm at Smaart class this weekend that it is just the "luck" of pure timing being between samples at 48kHz....as was speculated...
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