0

I've recently bought a ModMic4 for my PC, but the signal level is very low and have to amplify it quiet a lot digitally, which introduces ton of white noise and I have to use noise supression which degrades the overall quality. I would like to get this microphone to it's full potential.

I've read that the ModMic requires a 5V bias power to have correct output levels. It seems very few PC sound cards can supply this on the mic input. I have an ASUS Xonar U7 MKII and also tried the Creative BlasterX G5 and my onboard Realtek audio. Neither of them worked well. I could purchase the official ModMic card, but I would like to keep the Xonar which has a better headphone amp for my DT 770 and use it's input.

Is there any way to add a power injector to the system? This should be something like a middle man on the Mic wire, and could be powered from USB if I'm not mistaken.

Mod: I've found the following electret microphone powering circuits: Powering microphones Which one of these would probably work?

Mod2: also found this thread here on StackExchange for battery powering microphones: How to provide power to a lavalier microphone? Would these work with my setup as well?

NagyI
  • 189
  • 2
  • 9

1 Answers1

2

You can use a simple DC-DC isolated converter that you can find online like this that you can power directly from USB.

And a 10uF capacitor and 2k2 resistor connected like below as the link you posted (Battery powered electret microphone):

schematic

simulate this circuit – Schematic created using CircuitLab

Damien
  • 7,827
  • 1
  • 12
  • 29
  • Are you sure you don't need a resistor in series with the power supply, at the very least? Otherwise how does the audio signal not get attenuated to nothing by the low impedance of the power supply? – nekomatic Feb 26 '19 at 12:13
  • Indeed I forgot it, i'll edit. Thanks pointing out @nekomatic – Damien Feb 26 '19 at 12:19
  • Thank you! What's the easiest way to isolate the sound card's bias power? If I'm not mistaken, one of the microphone jack rings carries the bias voltage. What if during plugin the above circuits positive line gets in contact with that? Will the two voltages add up for a short period and that's it? The ModMic capsule can tolerate up to 10V based on it's spec. – NagyI Feb 26 '19 at 13:06
  • The bias voltage supply should always have a resistor in series, as in @Damien's circuit here and also in the microphone powering circuits you linked in your question. (Otherwise the low impedance of the supply would act like a near-short-circuit for the audio signal, as per my comment on Damien's original schematic.) So briefly shorting the sound card bias supply to any other pole of the jack shouldn't damage anything as the resistor will limit the current. – nekomatic Feb 26 '19 at 13:52
  • @Damien I wonder if the supply from the DC-DC converter will need any additional filtering though, to cut out switching noise - have you tried this in practice? A simple RC filter might work, but if not then a stepup DC-DC followed by a linear regulator? – nekomatic Feb 26 '19 at 13:53
  • 1
    To add the cap will stop any DC bias going either way. – Damien Feb 27 '19 at 05:04
  • 1
    @nekomatic Since the supplied current is tiny, there shouldn't be much of switching noise. Linear regulator, despite what people usually think, is not good at filtering ripple (I used to believe the same). I think the simple way is to use a DC-DC converter with a switching frequency outside of the audible range if there are. But a LC or RC filter before the resistor is also a good idea. – Damien Feb 27 '19 at 05:08