Attenuator Circuit for Headphone output -> Microphone input

Thread Starter

smallsun

Joined Jan 21, 2021
15
Hi,
I have seen several different threads about this but they seem either unanswered, or the solutions have not worked for me..

My goal is the following:
I would like to connect the headphone OUTPUT from my electric guitar amp to my PC microphone INPUT (both are 3.5mm 3 pole jacks).
My current approach is the following:
1611267531029.png

I am using a voltage divider to attenuate the signal down to approx 6-16mV (depending on the value of the potentiometer), since I hear the mic input works between 0~20mV. The cap is there to protect the mic input

When connecting this to a computer input, the computer does not even detect a new microphone option. I have also tried using Audacity for the "Microsoft Sound mapper - Input" option, but no audio is picked up.

Could this be because the signal is usually much lower than 1V, thus making the signal too attenuated?
Or did I make a mistake by not keeping R and L separate thus creating a monosignal out of it?

Here's the link to the falstad-simulation in case someone is keen to play around with it (sorry for the length; did not want to send a shady tiny-url):

https://www.falstad.com/circuit/cir...AGs1jK2MKYILxgAi0Fg8ACyAEsgisAJIAOwADgBXF70IA

Any ideas?

Best regards!
 

sghioto

Joined Dec 31, 2017
2,363
Or did I make a mistake by not keeping R and L separate thus creating a mono signal out of it?
I wouldn't think so. On my computer just plugging in a cable with nothing connected on the other end will give me a notification.
I believe there's a switch on the jack that the computer monitors when something is connected.
 

Audioguru again

Joined Oct 21, 2019
3,177
Maybe the pc senses the 0.3mA to 0.5mA of DC current used by an electret mic, then activates the mic input?
Then try adding a 3900 ohms resistor to ground at the mic input.

EDIT: Wait a minute. A 1V signal feeding headphones would blow your head off! Increase the 100 ohms to maybe 1k.
 

Audioguru again

Joined Oct 21, 2019
3,177
The headphones lack does not produce a VERY LOUD signal of 1V to headphones. The level might be only 316mV RMS to be loud.
is 10k series pot is not a good volume control that should be a voltage divider.
 

Thread Starter

smallsun

Joined Jan 21, 2021
15
Maybe the pc senses the 0.3mA to 0.5mA of DC current used by an electret mic, then activates the mic input?
Then try adding a 3900 ohms resistor to ground at the mic input.
Interesting. Wouldnt I have to remove the cap in that case, since it blocks all DC current?

The headphones lack does not produce a VERY LOUD signal of 1V to headphones. The level might be only 316mV RMS to be loud.
is 10k series pot is not a good volume control that should be a voltage divider.
How come the magnitude of the resistors matters here? Isnt only the proportions between them the only thing relevant?
(the 100ohm resistor just goes to ground, so that wouldnt risk blowing anything off, right?)

Sure, with the headphones connected. With a 10K load probably 1 volt or more.
The values I am measuring (perhaps not in the most reliable way with multimeter) are generally below 50mV.
As said before, isnt just the proportion between the resistors the only relevant here, since it's a voltage divider?

Many thanks for your answers!
 
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