This article is just excellent.
But whats does it all mean?
Basically the normal PC (usb or pci sound card) usually has a mono input like this.
Its something soundblaster kicked off and for some reason they expect the bias resistor and blocking cap to be in the mic assembly (prob due to tuning to the contained electret)
So your standard mono mic input has tip=signal, ring=bias & sleeve=gnd and you can buy mics that are basically just an electret with the capacitor and resistor already included.
Standard TRS mics like the Boya I just reviewed for PC, Recorders & Cameras.
The 2nd type where its more unusual to have a stereo mic and not sure of the circuitry but its as if the soundcard contains a blocking capacitor and bias resistor.
These work with any mic as you can plug in a normal TRS mono/stereo mic and it will work, also mono TS mics that might be labelled as 3v phantom power (Don’t work on Mono sound cards).
Also you can just get any electret with negative to sleeve and positive to ring or tip to output on L/R channel.
Mono soundcards are less flexible as they expect a bias resistor on ring, blocking cap on tip.
So if your going to DiY with a mono you will need to add a resistor and cap to the electret as in the 1st image (2k2, 4.7uF aint a bad rule of thumb but consult the electret datasheet)
Both can be fed with external line signals with mono and stereo inputs to mono and stereo cards.
So posting again about soundcards as my experiments with a bias resistor and cap on mono cards didn’t go that well but never occurred to me to just not bother and just put an electret on a stereo usb card.
The results are far better than I expected and have me head scratching why my bias resistor/cap tries worked out so bad.
Anyway another real cheap way even if it has a minimum of soldering is an electret or 2 on a stereo usb.
Its £7.00 from scan and either connect a PC/Camera/Recorder 3.5mm TRS style mic or with a bit of simple soldering make your own which is just an electret soldered to a 3.5mm TRS jack cable.
I picked rubber grommet that needed cleaning of flash but hey still makes an easy mount with isolation and the quality is much dependent on the electret but you can get good electrets for £2.50 to not much over £0.20 for cheapos that are not that bad.
I wish it had a cable rather than 90’ adapter its a mini usb so easily sourced.
So yeah doing my usual and going round in circles but maybe the extra for a stereo USB sound card over mono is worth it and its not just for the extra channel but the flexibility of what mics you can use.
If you are in the US then Syba seems popular over there.
If EU then the same seems to be sold by Delock.