On Sun, 23 Aug 2015 18:07:32 -0700 (PDT), Bill Unruh wrote: >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.
It's the nature of unbalanced connections, that they are noisier than balanced connections. However, there are several ways to implement balanced IOs. Using two unbalanced mono input channels as a single balanced input channel is not one of that ways. Most important is that the output and input fit together, than to care about balanced or unbalanced. Cable length and impedance need more attention. The microphone might provide line output (unusual, but not impossible). The OP should consider to use microphone output instead and to use a pre-amp for the input. I suspect to care about cable length and impedance is more important than to fake a balanced input. I doubt that a faked balanced input using two unbalanced mono inputs of an elcheapo audio device is good for any kind of measurement or audio recording. Btw. there's always a discussion if the cold output should be open-circuit for balanced output to unbalanced input. So you could consider the unbalanced to unbalanced connections I posted as wrong. OTOH a connection of cold and ground is wanted for unbalanced output to balanced input. We could discuss the amount of cores of the cable, to provide the latter, but since this thread is about balanced to faked balanced, we could add a discussion about balanced to balanced grounding. The grounding between balanced IOs could also be done in different ways. >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. IIRC the OP even didn't mention if the microphone should be used for measurements or underwater vocal recording. We aren't talking about a professional solution, we are talking about the advantage to fake a balanced input when using a crappy user input device in combination with the balanced output of a measuring microphone. There's no advantage! We do not need to care about technical reasons pro and con a faked balanced input by two unbalanced inputs. We simply should notice that 1. relatively good balanced pre-amps are very cheap nowadays and 2. they were more expensive years ago, when nobody considered to make two unbalanced inputs of home recording gear a faked balanced input. Why wasn't this done? Nobody was brilliant enough to think about this superp idea? "Unbalanced stereo input as balanced mono input" is an utterly wrong idea. I recommend to get a cheap, but anyway relatively good microphone pre-amp or directly pay for a better audio card with an integrated microphone pre-amp and FWIW to use defaults regarding the grounding, IOW not to modify gear and to use averaged, common cables. If getting new equipment shouldn't be an option, I would use the provided IOs as they are and not fake a balanced input. 2 Cents, Ralf ------------------------------------------------------------------------------ _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
