In Part 3 I said "Gain before Feedback" is partly a deception. Let me open that up — because the slogan really does work, but the reason isn't what it looks like. The first factor is the desk's latency. If the processing delay is above 3 ms, feedback naturally builds later — because you're delaying and breaking the feedback wave. On some desks, once you use everything, the average latency climbs to 8–12 ms. I turn that into an advantage: when the PA is hitting the room hard, I give the main system an appropriate delay. The best example is Jolly Joker İstanbul. The real issue there isn't only feedback; the soloist's ear is closer to the PA than to the monitors. Anyone who knows the Haas effect knows that whichever source is nearer, perception localizes to it "first." So in that room, every artist wants to push the monitors to overpower the PA. But give the PA a 3 ms delay and the problem gets much easier to solve. The second factor is the sound of the gain. The more low-mid harmonics blend into the main signal, the later those channels feed back — but once they go, they're hard to recover. The roomy frequencies that hit the mic first from the environment are the mid-mids and highs, the energy that returns first off the walls; those ring first, then the subs, and the low-mids come in last. So on some desks the low-mid harmonic character is dense from the start, and it changes how feedback behaves.
That's where the feeling of "unlimited gain" comes from: delay and harmonic balance push the feedback back. Not magic — physics. Have you ever solved the "monitor war" by deliberately delaying the PA?