Hello, I'm trying to make a headset's microphone work in a Lexicon Alpha but I'm failing miserably.
The headset has a TRRS 1/8 jack and comes with a splitter that is turns it into 2 TRS 1/8 jacks (Why the mic one is TRS and not a simply TS is beyond me.)
Either way, I tried using a TRS to TS 1/8 adapter so it's a mono signal and then that into a TS 1/4 jack and tried plugging it into the "Instrument input" in my Lexicon Alpha USB interface, but I don't see any input.
Is there something I'm missing?
The USB interface has the following inputs:
- Microphone Input: Female XLR Pin 2 Hot
Input Impedance: 600 Ohms balanced
GAIN: +50 dB
EIN: −115 dB A-weighted @ +50 dB gain (150 Ohm source impedance)
Maximum Input Level: –7 dBu
Frequency Response: +0, −0.5 dB 20 Hz - 20 kHz, ref. 1 kHz
THD+N: <.005%, 20 Hz - 20 kHz
- Line Inputs: (2) 1/4" TRS balanced or unbalanced
Input Impedance: 20 kOhm balanced, 10 kOhm unbalanced
Maximum Input Level: +13 dBu
Frequency Response: +0, −0.5 dB 20 Hz - 20 kHz, ref. 1kHz
THD+N: <.009% A/D, 20 Hz - 20 kHz
- Instrument Input: (1) 1/4" mono jack
Input Impedance: 1 MOhm unbalanced
Maximum Input Level: +8.5 dBu
Frequency Response: +0, −1 dB 20 Hz - 20 kHz, ref. 1 kHz
THD+N: <.0125% A/D
The headset has a TRRS 1/8 jack and comes with a splitter that is turns it into 2 TRS 1/8 jacks (Why the mic one is TRS and not a simply TS is beyond me.)
Either way, I tried using a TRS to TS 1/8 adapter so it's a mono signal and then that into a TS 1/4 jack and tried plugging it into the "Instrument input" in my Lexicon Alpha USB interface, but I don't see any input.
Is there something I'm missing?
The USB interface has the following inputs:
- Microphone Input: Female XLR Pin 2 Hot
Input Impedance: 600 Ohms balanced
GAIN: +50 dB
EIN: −115 dB A-weighted @ +50 dB gain (150 Ohm source impedance)
Maximum Input Level: –7 dBu
Frequency Response: +0, −0.5 dB 20 Hz - 20 kHz, ref. 1 kHz
THD+N: <.005%, 20 Hz - 20 kHz
- Line Inputs: (2) 1/4" TRS balanced or unbalanced
Input Impedance: 20 kOhm balanced, 10 kOhm unbalanced
Maximum Input Level: +13 dBu
Frequency Response: +0, −0.5 dB 20 Hz - 20 kHz, ref. 1kHz
THD+N: <.009% A/D, 20 Hz - 20 kHz
- Instrument Input: (1) 1/4" mono jack
Input Impedance: 1 MOhm unbalanced
Maximum Input Level: +8.5 dBu
Frequency Response: +0, −1 dB 20 Hz - 20 kHz, ref. 1 kHz
THD+N: <.0125% A/D
The headset's microphone probably requires a phantom supply that is very different from the ones used for professional microphones. It's usually a 2.2 kohm resistor to a supply voltage between 1 V and 10 V. See post 2 of this thread: https://www.diyaudio.com/forums/everything-else/352655-advice-weird-project.html#post6159191 (A phantom supply for professional microphones usually consists of two well-matched 6.8 kohm resistors to a 48 V +/- 4 V supply, one resistor for pin 2 and one resistor for pin 3.)
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You say that normal TRRS inputs like the ones in a laptop (tried a Macbook) or a cellphone (Samsung S9), where this headset mic works ok, provide power to the microphone to work?
For further reference, the headset is a Cooler Master MH751, a common gaming headset.
For further reference, the headset is a Cooler Master MH751, a common gaming headset.
Yes. The microphones are usually cheap electret condenser microphones with a built-in preamplifier (typically just a JFET connected as a common-source stage). The laptop / sound card / whatever needs to supply power to get the preamplifier to work.
Does your USB interface's microphone input have a 12 V or 48 V phantom supply for professional condenser microphones or none at all?
Does your USB interface's microphone input have a 12 V or 48 V phantom supply for professional condenser microphones or none at all?
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While it makes sense, i don't understand how the power is transmitted using the TRRS pins in a cell phone input, to me, one is ground, other 2 are for audio channel stereo output and the other is for the mono microphone input.
For this to work I'd expect another contact, how does it work?
For this to work I'd expect another contact, how does it work?
There is a pin that's used for both the microphone signal and the power to the microphone. See the schematic on page 2 of https://cdn-shop.adafruit.com/datasheets/CMA-4544PF-W.pdf , everything to the right of Term.1 and Term.2 is part of the cell phone / sound card / whatever.