Additional Features for Analog Inserts

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This topic contains 2 replies, has 2 voices, and was last updated by Profile photo of ParkerA1996 ParkerA1996 7 months, 1 week ago.

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    Profile photo of ParkerA1996

    Hey dLive users:

    I have run into some strange issues with clipping/headroom over the past months when adding analog gear into my dLive setup for insert style processing. Initially I was having gain issues where even an XLR loopback was increasing the level of a signal passed through a pair of ports. Nicola was quite helpful with this problem and suggested that those surface ports may have been recalled by a scene or otherwise that could have caused their gain values to be skewed. Unassigning and reassigning the ports to be inserts successfully fixed this problem, however, clipping distortions still persisted through XLR loopback and analog gear. After much testing with an Audio Precision analyzer, here are the results we have found.

    An XLR loop with “Insert” setting assigned to Analogue measures ~0 dB of gain. I cannot seem to figure out what the digital setting does when assigned to analog surface ports.

    Surface Inputs clip @ +18dBu (tested and verified)
    Surface Outputs clip @ +23dBu (+22.8 as tested)

    A Tie Line directly from an Input port to Output port measures +5dBu of gain. Sending such signals through a channel produce the same gain figure, unless the socket’s Pad is engaged and turned to 0dB first.

    This leads to the problem experienced – there is no gain across an insert, such as an XLR loop in this case, however when outputs (insert sends) are driven above +18dBu output, they will inevitably clip the insert return. This creates problems when a signal may not be clipping anywhere in a signal chain, however by assigning an insert, it immediately clips. I have set the final limiter section of my Stereo Bus processing to +18dBu and tested to ensure that clipping does not occur, however this is not an ideal situation.

    Ideally, it would be great for output ports to “recalibrate” when assigned to an insert path, meaning that now 0dBFS is related to +18dBu to ensure that input and output have the same clip point. I’m not quite sure if there is a way to do this in the analog domain, or if it is necessary to make software changes to how inserts are handled, but I am anxious to hear any ideas!

    Thank you!

    Profile photo of SteffenR

    What do you expect? It’s all written in the system specs.

    The sound engineer is responsible for the gain staging.
    Since preamps involved in analog insert chains, it is mandatory to do appropriate gain staging.

    Profile photo of ParkerA1996

    I am mainly asking if there is a way (or any ideas) to fix this issue, as it could cause newer or inexperienced engineers to unknowingly clip an insert mid show while operating within an otherwise “safe” gain structure.

    I don’t know of any dedicated line level IO cards for DX32 or similar at this point, and I suspect the Prime IO cards would have the same issue. Of course I could run everything over AES (or another multichannel standard) to a converter elsewhere that does all the analog bits and just sends back digital signals, but that’s also a large additional expense without even considering the AES IO that needs to be added with card slots or a DX32.

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