Question How to Transform a TRS Hp Output into a Microphone input ?

Oct 13, 2020
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Hi!
🤞Goal : Transforming the Direct Monitoring Output of the Focusrite into a Mic input (so that I don't need any numerical compatibility between devices, such as USB, drivers, etc), allowing to use any mix plugged into the interface, including 48V/Phantom power ones, on any device, 100% analogically.
Of course, I came to that idea, since I couldn't make the USB interface work on the smartphone, for every mic usage, notably rec & calls. Couldn't use apps through Windows PC either; the "My phone" Windows App was supposed to allow that, but it never worked for me & seems so unreliable anyway (Force close all the time, ppl saying it cancels calls randomly...); Samsung Dex is also an app very close from achieving it (it probably could in the future?), but the feature is just not available, only audio Phone→PC is supported... & I don't want wireless apps like Airdroid, wire = no data spying, best quality + reliability, - battery drains, & no Wi-Fi required in order to work (I actually have no Wi-Fi 😅)...

👉 Material :
♦ Focusrite Scarlett USB Interface, with XLR 48V mic
♦ Android phone (Galaxy S10e), with 3.5 hp jack ; High Res Audio Recorder & Call apps
♦ TRS & TRRS 3.5 male² cables ; TRS cable cut on 1 hand for experiments
♦ This TRRS screwable adapter: https://www.amazon.fr/gp/product/B08CVM2T31
♦ this Male TRS ↔ Female TRRS adapter for mics: https://www.ebay.com/itm/3-5mm-3-Pole-TRS-male-TO-4-Pole-TRRS-Female-Microphone-Jack-converter-Adapter/224045325396 (converts TRRS mics like SmartLav+ into TRS mics, making them compatible with smartphones → cameras) ; equivalent to the Rode adpter : https://www.ebay.fr/itm/Replacement-SC3-Microphone-Cable-for-Rode-Female-TRRS-to-3-5mm-TRS-Male-Adapter/224088834243
♦ This TRRS Mic/Hp splitter: https://www.ebay.com/itm/Ugreen-Headset-Adapter-Headphone-Mic-Y-Splitter-Cable-3-5mm-Male-to-2-Female-PS4/152594143413
♦ OMTP/CTIA converter: https://www.ebay.com/itm/3-5mm-Jack-CTIA-to-OMTP-Earphone-Converter-Metal-Male-to-Female-Audio-Adapter/324299553568

👇Experiments : [Spoiler: All FAILED 😭]
I mean, hold on... no, hang on!
→ Plugging the splitter to the phone, & the USB interface to the PC for power & tests, will be all along the tests; keep in mind the splitter makes the mic signal equivalent to a TRRS mic, when it comes to which pole transfers the signal (Sleeve).
→ As a contextual validation: Smartlav+ Rode mic → [Male TRS ↔ Female TRRS adapter for mics] → Splitter on mic side→ Smartphone : 🍾WORKS✅ 🍾(redundancy of TRRS→TRS→TRRS)

• Interface output → OMTP/CTIA converter → TRS Male² cable → Splitter on mic side → Smartphone : Fail
• Interface output → TRS Male² cableOMTP/CTIA converter → Splitter on mic side : Fail
• Interface output → TRS Male² cable [Male TRS ↔ Female TRRS adapter for mics] → Splitter on mic side : Fail
• Interface output → [Male TRS ↔ Female TRRS adapter for mics] (reversed)TRS Male² cable → Splitter on mic side : Fail
• Interface output → OMTP/CTIA converter TRS Male² cable[Male TRS ↔ Female TRRS adapter] → Splitter on mic side : Fail
• Interface output → OMTP/CTIA converter [Male TRS ↔ Female TRRS adapter] (reversed)TRS Male² cable → Splitter on mic side : Fail
• Interface output → TRS Male² cableOMTP/CTIA converter [Male TRS ↔ Female TRRS adapter] → Splitter on mic side : Fail
• Interface output → [Male TRS ↔ Female TRRS adapter] (reversed)OMTP/CTIA converterTRS Male² cable → Splitter on mic side : Fail
• Interface output → TRS Male² cable[Male TRS ↔ Female TRRS adapter]OMTP/CTIA converter → Splitter on mic side : Fail
• Interface output → [Male TRS ↔ Female TRRS adapter] (reversed)TRS Male² cableOMTP/CTIA converter → Splitter on mic side : Fail

• Plugging TRRS Male² cable didn't change anything from TRRS, since the interface output is TRS, so discard this option right away. Just wanted to try in case voodoo stuff would happen 😇
• Partially insert of jacks, in all previous cases: Fail; the app stopped recordings most of the time, as it does when a mic is unplugged, bc it "fake-detected" 1 in & out. Yet, I remember & of these tests gave a successful signal while unplugging, but not on a steady position! Which gave me the hope it would work on below experiments...

→ Now, I was convinced the solution hinged on building a custom cable, as it might be a matter of ground placement/commuting/shunted...
→ My TRS cable cut on 1 hand for experiments, gave me 5 headaches, just to figure out which wire was what, since it had 5 non standard colored wires... By trying & error, found out the L, R, & all the others considered as Ground, so joined together.
→ Now, on the TRRS screwable adapter: considere the correct wiring (for TRS cable) is: L wire ↔ T ; R wire ↔ R1 ; Ground ↔ R2 ; Ø ↔ S
→ For tests, L & R are reversible, since it's just a matter of signal/ø ; what could eventually make a difference in term of power/current/resistance (then detectability?) was L+R.

• Plugging (screwing) L, R & Ground properly (verified working), creating a straight TRS cable : Fail (of c, otherwise none of that would be necessary...)
• L wire ↔ T : Fail
• R wire ↔ R1 : Fail
• L wire ↔ T ; Ground ↔ R2 : Fail
• R wire ↔ R1 ; Ground ↔ R2 : Fail
• L wire ↔ T ; R wire ↔ R1 ; Ground ↔ S : Fail
• L wire ↔ T ; R wire ↔ R1 ; Ground ↔ R2 + S (Shunted) : Fail
L + R wires ↔ R1 ; Ground ↔ R2 : Fail
L + R wires ↔ R1 ; Ground ↔ R2 + S : Fail
• L wire ↔ T ; R wire ↔ R1 : Fail
• L wire ↔ T ; Ground ↔ R1 : Fail
• R wire ↔ R1 ; Ground ↔ T : Fail
• L wire ↔ T ; R wire ↔ R1 ; Ground ↔ : Fail
• L wire ↔ T ; Ground ↔ R1 + R2 + S : Fail
• L wire ↔ R1 ; Ground ↔ T + R2 + S : Fail

Conclusion: I'm officially utterly PISSED OFF If none of those worked, the only remaining explanation to me, is there is some difference between Mic in & any device output. But can't figure out which one.. Power? Couldn't try every step on the potentiometer obviously, but nor 0, nor low, neither high gain did change a thing. Resistance? I tend to think so.

👉 "So the next step for us is to figure out how to hotwire the signal from the PC to the external Mic and trojan horse it " 👍, PC being USB interface's monitor output in my case (even though having the signal going through the PC is applicable as well). Any TRS output basically.
Ideas?
 

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