I have an issue with my headset. I can’t stand not being able to hear myself speak. I’d like to build a passive device to loopback the mic to the headphones that would be plugged in-line between the headset and device, with a potentiometer to adjust the mic volume to headphones.
Would it be as simple as this?
Are additional fixed resistors required? I assume it would be a good idea to put something in series with the pot for when it is turned up fully, but I’m not sure what size..100ohm?
The headset speaker impedance is 32ohms each and the microphone impedance is 2200 ohms. I’m not sure of the impedances of the device, it can be assumed to be a typical laptop computer or smartphone.
As for power ratings, I assume the typical voltage at max volume would be less than 1V for the headphone jack on these devices. So, would a standard 0.06W dual gang logarithmic pot would be adequate for this application?
Appreciate the help on this.
Thanks for everyone’s feedback. I’ve added an amplifier with variable gain for the mic input to the best of my understanding, but I’m not sure about splitting/mixing the signal. Will I be able to do this passively without any more amplifiers? Would anyone suggest different values for resistors/capacitors? Any other errors?
EDIT 2: New question
I’m looking to create a circuit to add sidetone to a headset. Looking to add it to both right and left channels, with a volume adjustment. The circuit would be connected in-line between the headset and the device to which it is connected (laptop, smartphone, etc). The device would be powered by 2AA batteries.
The speakers on the headset are 32ohm and the microphone is 2200 ohm.
Would this even work?
Could the number of amplifiers be reduced?
Could the number of pots be reduced? Note that there would probably be 3 off 2-gang pots, as there is no need for balancing between right and left. There is also no need for master volume control, but I’m worried I won’t be able to select the proper resistor value.
Are the resistors/pots/capacitors sizes critical? If so, any suggestions?
Is it even feasible to run this off 2AA batteries?
Is there any risk of damaging the headset/device?
Amplifier data sheet for reference: https://www.njr.com/semicon/PDF/NJM2113_E.pdf
Since the amount of gain on preamp is unknown, would it make sense to add a potentiometer? If so, what min max values would you suggest?
Regarding your final statement on ground wiring, are you suggesting arranging the ground wires in a manner such as the below diagram:
When the circuit is powered (3V on) the mic output to headset is loud and clear, but the mic output to the device is very muffled and quiet. When the circuit is not powered (3v off) the output to the device returns to normal (and nothing can be heard in headset as the speaker amps have no power, of course). Connected to oscilloscope to demonstrate. Mic is picking up a loud tone from a tone generator. Cursor shows where circuit is switched OFF.
Yellow - M+
Green - Preamp Term 4
Red - Preamp Term 5
Blue - Input of Volume Pot
When switched off, preamp output goes to zero, and M+ signal goes to normal.
Any suggestions for retaining signal quality at M+ when circuit is powered ON?
To answer previous question on mic voltages (headset connected directly to device):
Vrms = 1.54V
Vp-p quiet = 44-56 mV
Vp-p talking = ~80 mV
Looking to clarify circuit:
Note I am using 100k POT for R1