On Mon, 24 Aug 2015, Gunnar Arndt wrote: >Btw, that noise is actually from the on-board wiring - it's there even >if nothing is connected to line input. If nothing is connected even the best discrete circuits could be noisy. For e.g. phono pre-amps it's common to insert short circuit connectors, when they are unused. >> Another analog hardware solution would be to use an audio >> isolation transformer in front of your digitizer. Radio Shack >> used to sell a fairly cheap audio isolation transformer that >> worked surprisingly well. A metal box for shielding is probably >> a good idea. >I'm not sure if I understand correctly what its purpose would be - >unbalance the signal, like what I know as an opposite DI box? >If you put under consideration that the noise comes from the mainboard >for the most part, you'll agree that it would not make sense to >unbalance the signal before reaching the mainboard, as some box would >require. It makes sense! Mic balanced -long-wire-> balanced in, circuit with transformer, unbalanced out -short-wire-> unbalanced in, mobo audio device If a transformer is the best solution for your usage is questionable, but it for sure is a better solution, than what you're doing. >I know that a better sound card is required - especially for the >frequency range: the mic goes down to 9Hz, whereas the current sound >chip goes only to 20Hz. Audio engineering isn't rocket science. A lot of quite good prosumer sound cards can't go lower than 20 Hz. Don't care that much about key data, such as signals that might have half of the level, than other signals or a wide frequency response range. The quality of circuits and signals depends on balance of a lot of specifications, that have to fit to the usage. Consider your faked balanced input as very "imbalanced". If you get rid of noise, you not necessarily win sound quality, let alone a linear or what ever kind of response that might be wanted for measurements. ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-user
