[Sursound] "Low cost" mobile ambisonic recording possible ?
I want to lighten my burden when traveling and maybe do a recording. I want to avoid spending much more money on this. So I want to put a few questions on the table. I can accept to carry the Motu Traveler as the Microphone inputs and the gain controls and level monitoring works well. So I want to build / assemble something low weight and small to add to the MOTU as a pure digital recording device. The MOTU can be configured as a mixer outputting ADAT or dual SPDIF for 4 channels. The Dual SPDIF signals have the eventual advantage of having a choice of 44.1, 48, 96 or 192 kHz sampling rate. So being as unstructured as I am I have a few wild ideas. My first question: - If using 2 USB sound interfaces with spdif inputs, should the audio interfaces not stay in sync as long as the input signals from the MOTU stays in sync? If so, This would make it possible to use 2 low cost USB audio cards with SPDIF inputs? - can this be correct? - Can dual SPDIF inputs be directly added to the RPi? - Can 2 I2S input modules be used http://www.pavouk.org/hw/modulardac/en_dir9001spdif.html and connected to a RPi, would the drivers be difficult to create? or maybe ADAT via I2S? Not so expensive ADAT receiver modules with I2S interface > http://electronics.dantimax.dk/Kits/Digital_audio/11329401182.html > http://www.pcm63.com/?332,adat-receiver-module A very simple recording program or App for 4 channels should be possible to create for the RPi on linux or Android, ardour is overkill. Analog Line in to Zoom H2 from the MOTU feels "not good enough" as it will be AD - DA - AD conversion. A much lower weight solution, but maybe lower quality overall? Have someone created a small circuit to interface the coresound directly to a ZOOM H2? My idea for this would be: - External Battery feed to the ZOOM H2 to redusing internal voltage converter disturbance signals, 6 Volt to the coresound mic, could the Tetramic capsules be directly connected to the H2, maybe a Capacitor needed to isolate DC levels? Currently I have and use this hardware: Coresound tetramic Motu traveler MK3 Large Toshiba A100 portable PC. Zoom H2 - not modified ( yet with 4 line inputs ) use as backup in case of problems with primary system. On Order: Raspberry Pi 2 USB Soundcard with SPDIF input http://www.amazon.com/dp/B000XXY5Q4/ref=pe_175190_21431760_M3T1_SC_3p_dp_1 - Bo-Erik ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] "Low cost" mobile ambisonic recording possible ?
i can answer one question. i have built an adaptor for a modified zoom h2 to core sound. just a small box with a nine volt battery, four three pin mini xlrs to take the core sound signal. you can safely apply the nine volts to the core sound +ve connection. the zoom itself can be modified so the four internal microphone connections can be directly brought out to a five pin xlr, (i have published this mod with a small part made at shapeways.) i built a system like this for john leanord in this group, but made several mistakes mostly by being over elaborate. no need for a regulated five volt circuit, or for additional gain either (the core sound mic has very low output). John said my circuit eats batteries, but that is because of the quad opamp gain circuit. umashankar > From: bo-erik.sandh...@ericsson.com > To: sursound@music.vt.edu > Date: Tue, 2 Oct 2012 16:30:42 +0200 > Subject: [Sursound] "Low cost" mobile ambisonic recording possible ? > > I want to lighten my burden when traveling and maybe do a recording. I want > to avoid spending much more money on this. > So I want to put a few questions on the table. > > I can accept to carry the Motu Traveler as the Microphone inputs and the gain > controls and level monitoring works well. > So I want to build / assemble something low weight and small to add to the > MOTU as a pure digital recording device. > > The MOTU can be configured as a mixer outputting ADAT or dual SPDIF for 4 > channels. > The Dual SPDIF signals have the eventual advantage of having a choice of > 44.1, 48, 96 or 192 kHz sampling rate. > > So being as unstructured as I am I have a few wild ideas. > > My first question: > - If using 2 USB sound interfaces with spdif inputs, should the audio > interfaces not stay in sync as long as the input signals from the MOTU stays > in sync? >If so, This would make it possible to use 2 low cost USB audio cards > with SPDIF inputs? > - can this be correct? > > - Can dual SPDIF inputs be directly added to the RPi? > - Can 2 I2S input modules be used > http://www.pavouk.org/hw/modulardac/en_dir9001spdif.html and connected to a > RPi, would the drivers be difficult to create? > > or maybe ADAT via I2S? > Not so expensive ADAT receiver modules with I2S interface > > http://electronics.dantimax.dk/Kits/Digital_audio/11329401182.html > > http://www.pcm63.com/?332,adat-receiver-module > > A very simple recording program or App for 4 channels should be possible to > create for the RPi on linux or Android, ardour is overkill. > > Analog Line in to Zoom H2 from the MOTU feels "not good enough" as it will be > AD - DA - AD conversion. > > A much lower weight solution, but maybe lower quality overall? > Have someone created a small circuit to interface the coresound directly to > a ZOOM H2? > My idea for this would be: > - External Battery feed to the ZOOM H2 to redusing internal voltage converter > disturbance signals, > 6 Volt to the coresound mic, could the Tetramic capsules be directly > connected to the H2, maybe a Capacitor needed to isolate DC levels? > > Currently I have and use this hardware: > Coresound tetramic > Motu traveler MK3 > Large Toshiba A100 portable PC. > > Zoom H2 - not modified ( yet with 4 line inputs ) use as backup in case of > problems with primary system. > > On Order: > Raspberry Pi > 2 USB Soundcard with SPDIF input > http://www.amazon.com/dp/B000XXY5Q4/ref=pe_175190_21431760_M3T1_SC_3p_dp_1 > > - Bo-Erik > > > > > > > ___ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20121002/dff5456c/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
[Sursound] Mobile sound, calibration, planar waves
Greetings All, Regarding mobile recording rigs, their seems to be belief that any recording device or preamp that uses rotary pulse encoders in lieu of potentiometers is intrinsically dead accurate across channels. For this reason, a lot of folks avoid using recording devices with conventional pots for their Ambisonic recorder. I personally prefer NOT to bring my laptop with outboard hardware (e.g., MOTU Traveler) into the field unless absolutely necessary. I really like the sound and quality of my Edirol Roland R-4 Pro. Very low noise preamps (purportedly better than the R-4 without "Pro" suffix) and it's super easy to use. But it has those horrible pots we abhor. Actually, the concentric level adjustments on the R-4 have a conventional pot on the inside and what appears to be an encoder on the outside. With the pots fully CW, the gain adjustments are uniform across channels. Gain is displayed digitally on the display when using the outer gain knobs. I confirmed accuracy across channels with a balanced output calibrator I built. Briefly, my "calibrator" is nothing more than a THAT Corp. balanced line driver, tone generator, and low-noise attenuator using Vishay resistors. Low-noise circuitry is needed because we're dealing with mic-level (mV) signals. The balanced line driver precludes the need for a pseudo-balanced (really single-ended) signal feeding the R-4 Pro's balanced (XLR) inputs. All in the name of low noise... even with short cable leads. In the end, this calibrator could be of benefit to those who may not know whether their digitally-controlled attenuators are truly equal across all channels. I've seen researchers assume the voltage or attenuation at a device's port is exactly what their MATLAB (or whatever) codes says it should be; they didn't consider the effects of buffer resistors, loading, etc. These effects are generally not accounted for in the software, on a computer screen, or other digital displays. Hardware calibration isn't a bad thing at all! RE plane waves: I saw the recent discussions regarding waves and wavefield reconstruction. I'm not one of those persons who solves Legendre polynomials in my sleep, so I avoided putting in my 2 cents worth. But I do have a question/comment. Some years ago, I recall seeing articles on psychological warfare and an acoustical "laser" that had commercial application, too. I can't find those references (or my folder with the related JASA article, etc.), but now I question what I read. Anyway, it seems that a sound arriving at the ear from a coherent sound source would have to be "planar" but of fixed, or finite, area. Waves emanating from a source or many sources (such as a water fall) approximate plane waves as they become distant from the source. But the "area" as well as distance of plane waves would be quite large (infinite if we assume the wave is shaped like the surface of a sphere). Because of differences in how planar waves can be generated, wouldn't there be differences in how these waves diffract around and interact with the head, pinnae, etc. In other words, "head shadow" would vary even when the wave generating sources' direction and angle remained the same. In some ways, this would be akin to comparing shadows from conventional light to laser light (assuming no reflecting surfaces to create diffuse light). Just some thoughts... and probably has some bearing on localization experiments performed in near field versus far field listening environments (??). Thanks to everyone here for your help, ideas, and suggestions that have propelled me along in my research endeavors. My latest explorations have involved deconvolution and swept-sine sources using my TetraMic. (I use a KRK 9000 monitor as my source along with a battery operated "high-end" amplifier. Still trying to create the Holy Grail of "real-world" stimuli for hearing science and cochlear implant research. Eric -- next part -- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20121002/8de425de/attachment.html> ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
Re: [Sursound] "Low cost" mobile ambisonic recording possible ?
Bo-Erik Sandholm wrote: I want to lighten my burden when traveling and maybe do a recording. I want to avoid spending much more money on this. Consider using a Tascam DR-680. It's available in the US for under $700 and has good mic pre-amps with digitally set levels. It is very convenient and reliable for recording with TetraMic. Len Moskowitz (mosko...@core-sound.com) Core Sound LLC www.core-sound.com Home of TetraMic and PDAudio ___ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
