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Message: <blockquote data-quote="John Roberts" data-source="post: 68233" data-attributes="member: 126">Re: How to do an analog insert?Not to continue this veer but it matters quite a bit for accuracy of gain sharing under different source conditions. A distant sound source that is picked up equally by multiple mics, or say from one talker equidistant from two mics would be roughly coherent and combine linearly, so gain calculation assuming incoherent would be incorrect. One powerful application for AM is reducing feedback from a room monitor speaker when many open mics are involved. Imagine a monitor speaker sound signal being picked up by 10 open mics, worst case if this speaker is equidistant from each mic, they could sum to roughly 10x one mic (not exactly), but if ASSumed to be incoherent sources for gain sharing, the per channel gain would only be reduced by SQRT 10, resulting in less dB margin before feedback occurs.  AM is a premium solution for managing a large number of open mics. The Dugan algorithm portions out the gain per channel so the total gain in all channels combined is equal to one mic at full gain. You could do this manually by riding faders, but not easily. Gating does not resolve the scenario when multiple channels inputs are above threshold so open up.. Enough people talking at the same time could start feedback, and the gates are not going to close once the feedback starts. If the system doesn't feedback with all the channels open you probably don't need AM. Again I apologize for veer. JRPS: For TMI years ago I did design a cheap NOM AM input module solution for install mixer-amp products, where each mic input had a gate threshold, and when that channel turned on, it dimmed all the other channels a fixed amount. Cheap and crude, but rough NOM correction for use in a budget install product.</blockquote>

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