🎯 Two rooms, two grounds: the voltage between them rides the ch 2 and 20 pairs into the Trident

🔌 The buzz lives on the mic-closet leg; the Trident leg tests clean

⏱️ 33 tests between 20:22 and 22:04 PDT ended at “I'm stumped”

1. T1 · 20:22Amps and monitors on, all monitors, solo masterch 2✕ buzz

   “So, yeah, that's clear that that's bad.”

2. T2 · 20:29Pull the Ethernet at the back of the mic-closet Catapultch 2▼ gone when removed

   “if you unplug channel two here, that stopped it. / Completely? Completely. No buzz.”

3. T3 · 20:30Pull a second item on the ch 2 path into the GX (not named)ch 2▼ gone when removed

   “That also stopped it.”

4. T4 · 20:30Pull the SLink Ethernet, GX to SQ-7ch 2? unclear

   “That did not stop it when I unplugged that. / That did stop it.”

5. T5 · 20:31SQ-7 powered offch 2✕ buzz

   “This is off, and that didn't take it up.”

6. T6 · 20:31GX4816 power removed entirelych 2✕ buzz

   “To power out entirely, the buzz is still there. But if I take this out, the buzz goes away.”

7. T7 · 20:32Check whether GX aux outputs hit ch 2ch -- n/a

   “These are auxes. So these are for PAs and in ears and monitors.”

8. T8 · 20:33Swap the XLR patch, Catapult to GX ch 2, for another mic cablech 2✕ buzz

   “It's still there. Still buzz? Yeah. So it's not this cable.”

9. T9 · 20:35Unplug GX aux output cables one at a timech 2✕ buzz

   “none of them fully did it. Some of them had a minor effect on it, but it was an inconsistent effect.”

10. T10 · 20:37Same pull test on ch 20ch 20▼ gone when removed

    “Does it still go away? Makes it go away.”

11. T11 · 20:39Pull a patch: wrong one first, then ch 2. Hiss and buzz heardch 2▼ gone when removed

    “There's a hiss and a buzz. When I take this out, the buzz goes away.”

12. T12 · 20:39Plug the ch 2 patch back inch 2✕ buzz

    “Because I've plugged that back in and now it's there.”

13. T13 · 20:40GX off and SLink out togetherch 2✕ buzz

    “Which means it's neither the connection to the SQ7 nor the power.”

14. T14 · 20:41Touch the box and connectorsch 2✕ buzz

    “Still there? It's still there.”

15. T15 · 20:43Move the Ethernet between Catapult ports so the channels changech 2? unclear

    “That did fix it ... that actually would mean that it is the Ethernet.”

16. T16 · 20:46First Ethernet tester on several cables: pin readings jump aroundch -? unclear

    “this tester must be busted”

17. T17 · 21:05Plan an end-to-end loop test with a couplerch -- n/a

    “We just need a coupler, and we need to get a long Ethernet cable around back around in the loop”

18. T18 · 21:06Second tester on the original Cat6ch -✓ clean

    “I'm getting green on all of them. So, the Ethernet's okay.”

19. T19 · 21:11Unplug GX inputs 1 and 3 to 8, keep 2ch 2✕ buzz

    “try three 4, 5, 6, 7, 8. Okay, so no.”

20. T20 · 21:14Unplug the rest of the GX one by one, power, SQ-7 offch 2✕ buzz

    “The only thing is this and this and the Ethernet.”

21. T21 · 21:17Inspect the rack; buzz louder with Greg's body closech 2✕ buzz

    “it's worse when I'm here. I hear like a big buzz there.”

22. T22 · 21:20Proposed snake cable test, declined as donech -- n/a

    “we did test a different XLR. It was doing the same thing.”

23. T23 · 21:21Ch 20 pull test repeatedch 20▼ gone when removed

    “Yeah, 20 does the same.”

24. T24 · 21:24Ch 20: Ethernet out vs XLR outch 20▼ gone when removed

    “Just taking the Ethernet cable out cuts the buzz entirely ... Taking out channel 20 ... Very late [light] buzz”

25. T25 · 21:26SQ-7 on, SLink Ethernet outch 2✕ buzz

    “when we unplugged the S-Link stuff, that Ethernet, it didn't cut the buzz.”

26. T26 · 21:27Phantom power on ch 2 switched offch 2? unclear

    “Oh, that's cut that off, phantom.”

27. T27 · 21:27Compare 2 and 20; lower gain on 20ch 20✕ buzz

    “This actually has less gain. Did that do anything? No.”

28. T28 · 21:35Source straight into GX ch 2, Catapult bypassedch 2✓ clean

    “direct into this into that into there, clean.”

29. T29 · 21:43Find and run the unused silver Cat6 between Catapultsch 2- n/a

    “Okay, it's plugged in.”

30. T30 · 21:51Listen through the new cablech 2 / 1✕ buzz

    “Clean. / Oh, it's not Clean. ... What about channel one? Very clean.”

31. T31 · 21:52Reasoning on the new cablech 2✕ buzz

    “that would be too random for that to cause the same problem on the same channel.”

32. T32 · 21:59Pull the new Ethernetch 2▼ gone when removed

    “Did you did this cable fix it? Oh, no.”

33. T33 · 22:04Plan: everything electrical off, original Ethernet back inch 2· not tested

    “turn just turn everything off and see if the buzz goes away.”

🔁 Eight calls flipped or fell apart within the evening

🧠 One mechanism explains all ten observations

• 📅 2026-01-22 and 2026-08-03Every orange IG outlet tested reads open ground; neutral-to-ground floats 30 to 60 V
• 📅 Documented wiringGX outputs feed the Crown amp on the Furman, PSM900 in-ears, and subs on their own outlets: the GX chassis stays tied to ground with its cord pulled
• 📅 ~2026-03-16Channels 2, 20 and 22 logged down / crossing; bypassing the Catapult cleared ch 2 then too
• 📅 2026-08-03Handoff: loud buzz when 48 V phantom is engaged, mostly on Live Room mic lines
• 📅 At installCrew pressed Catapult ground switches until it worked; lift positions never recorded
• 📅 DocumentedLights and audio share a panel; Lutron dimmers on control-room and iso-room track lights
• 📅 2026-09-12Trident ch 26 reported buzzing; not retested tonight. Trident Star Ground Link state unrecorded

🎯 GX input vs Catapult channel is a coin flip; the ground difference is near certain

⚠️ v1 ranking from 20:00 to 22:05. Superseded by the v3 line-up above.

• C1 Imbalance inside GX4816 inputs 2 and 20

  Confidence: moderate

  Matched phantom resistors; a hot-patch with phantom on or a static event takes one out. Phantom LEDs look lit on some inputs in rows 1 and 2

• C2 Imbalance in the mic-closet Catapult, channels 2 / 20

  Confidence: moderate

  Same symptom, different box. The swap test separates C1 from C2

• C3 Ground potential difference drives every case

  Confidence: high

  High that it exists, given the open IG ground. Bonding the IG bus to service ground lowers the whole floor

• C4 Phantom from two consoles on one line

  Confidence: low-moderate

  48 V pushed through the passive split into the other console's input network. Untested (T26 result missing)

• C5 Split pair in the Cat6 termination

  Confidence: low

  Explains one channel but not surviving a full cable swap

• C6 A specific noise load

  Confidence: unknown

  LED drivers, dimmers, Lorex camera PoE switch, PA amps on the GX auxes, HVAC. The all-off test (T33) never ran

✅ v1 test list: seven short tests, now folded into the v3 tree

1. D1Swap test⏱️ under 10 min

   Mic-closet Catapult out 2 into GX input 1, Catapult out 1 into GX input 2. Repeat with 20 and 16

   ➜ Buzz follows GX input 2 = GX input is the asymmetric part. Buzz stays on Trident ch 2 = asymmetry is upstream in the Catapult path

   👂 Buzz moves to Trident ch 1 = GX input 2 is the fault. Replacement or A&H repair is justified

   👂 Buzz stays on Trident ch 2 = the fault is upstream, in the Catapult path

   🔁 Then repeat with 20 and 16
2. D2Second grounded device⏱️ under 10 min

   Catapult out 2 into a known-good grounded input (QSC or a spare preamp) instead of the GX

   ➜ Buzz = Catapult / pair side. No buzz = GX input

3. D3Meter the grounds⏱️ under 10 min

   AC volts GX chassis to Trident chassis (long wire to the DMM), and between ground pins of the two racks' outlets, lights and HVAC on and off

   ➜ Above about 50 mV AC = a ground difference worth killing

4. D4Temporary bond⏱️ under 10 min

   Heavy wire (12 AWG) between the mic-closet rack and the Trident chassis

   ➜ Buzz drops = ground difference confirmed; RX4M modules in the mic closet end the loop, and the IG bus bond lowers the voltage building-wide

5. D5Phantom audit⏱️ under 10 min

   Read phantom on the Trident, SQ-7 and GX LEDs for 1, 2, 16, 20. Turn all four off and listen

   ➜ Shows whether C4 is in play

6. D6All-off test (T33)⏱️ under 10 min

   Original Cat6 in, buzz audible, kill circuits one at a time: lighting, HVAC, PA amps, camera / network switch

   ➜ The circuit that silences it names the noise source

7. D7Isolate the split⏱️ under 10 min

   Mic-level 1:1 isolation transformer on ch 2 between Catapult out and GX in (Radial TX4M/RX4M or an inline iso)

   ➜ Buzz gone = permanent fix: transformer-isolated modules in the mic closet

❓ Ten questions for Greg and Elijah close the gaps

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1. Which console had phantom on for channels 2 and 20 tonight, and is it off on 1 and 16? (Trident switches, SQ-7 scene, GX PP LEDs.)
2. In P15 (Catapult straight to the QSC), which channel number, and was anything else connected to that Catapult at the time?
3. In P13 (“speaker directly on the A&H channel”), where exactly was the speaker connected?
4. In T15 (Ethernet moved to other Catapult ports), did the buzz move to other channel numbers, stay on 2 and 20, or vanish?
5. Which Catapult module and bank carries channel 20 on each end, and are 2 and 20 on the same Cat6 run? Elijah's “16 and 20 on the same route” does not match 4-channel banks.
6. Which outlets feed the mic-closet rack and the mix-room rack, and are they IG (orange) outlets?
7. Is the Cat6 between rooms shielded, with shielded plugs at both ends?
8. Does the buzz change when the studio lights are dimmed, when HVAC cycles, or at a different time of day?
9. Did the mains all-off test happen after 22:05 PDT, and what happened?
10. Where is Elijah's paper test sheet?