Bill,
> He stated that if he ran the signal left and right with the ground as common > ground, he got lots of noise. > If he subtracted L from R the noise disappeared. > Now, that may mean that there is common mode noise, in which case running the > balanced into an unbalanced would be very noisy, or the noise was all in the > ground wire, in which case bal->unbal might work. > But there is another issue. He does not say if the mic is a battery operated > unit or a mains operated. If the latter, then the battle between the grounds > of his mic and his computer will produce lots of noise. If battery, then it > might work. That now he says: his mic battery operated it is. Bill assumes correctly that the noise is from the sound card - probably from the wire from the jack to the chip: it is even there if nothing is connected to the line input. And if the cold wire from the mic is just grounded, the noise is still there when recording the hot signal. > > Certainly I would agree that use of a better sound card would be advisable. > Note that he does not say what "measurements" he wants to do. If it is just > levels then the crappy sound card might do, but even freq response is liable > to be dominated by his the response of his sound card. And noise is almost > certainly dominated by the sound card. 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. As I had stated in the initial message, I am interested in the approach as an experiment, not for productive use. However, I like it for several reasons: - It requires only software, no additional hardware. - The mic is easily portable because of the integrated, battery-powered amp, so it is helpful if any computer can be configured with a few lines to use it properly (that word's gonna cause objection, I guess). - Grounding one line grounds halfs the amplitude as well - in other words, subtracting L and R doubles the amplitude, compared to a traditional approach. - It works! With the help of Clemens even in (almost) real-time. Regards, Gunnar > > > On Mon, 24 Aug 2015, Ralf Mardorf wrote: > >> On Sun, 23 Aug 2015 14:20:46 -0700, Robert M. Riches Jr. wrote: >>> That solution is to just ground one of the balanced wires and use the >>> other as signal. >> This (an unbalanced wiring) is the only sane solution for this kind of >> setup. >> >> Faked balanced input or real balanced input by using a transformer or >> what ever kind of cheap circuit won't help. >> >> After that it's possible to connect this mono signal to the left and >> right input, no de-coupling and no conversion is needed, but I anyway >> wouldn't do it. IMO the OP should record the unbalanced signal by the >> left or right channel only and split it to two mono signals by >> software, e.g. by jackd connections, assumed it should be needed. >> >> However, one issue still remains. Line input is not optimised for >> microphone output. Btw. I guess integrated consumer audio provides some >> kind of microphone input. It might be crappy, but likely better than >> any kind of connection to crappy line inputs. >> >> A cheap microphone pre-amp with line output might help when using mobo >> integrated audio too. >> >> For what purpose ever a measurement microphone might be good for, I >> doubt that usage with an on-board audio device makes much sense. >> >> ------------------------------------------------------------------------------ >> _______________________________________________ >> Alsa-user mailing list >> Alsa-user@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/alsa-user >> > ------------------------------------------------------------------------------ > _______________________________________________ > Alsa-user mailing list > Alsa-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/alsa-user ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
