I have just purchased a new Sony UWP wireless diversity system that I found at an exceptional price, and I am trying to maximize my investment at the same time that I am trying to maximize my flexibility. I am relatively new to the audio world, and I am still a bit ignorant about some issues, but I have been doing a lot of reading and probably now know enough to get myself in trouble!
Part of the kit that I have is a few instances of the UWP-V1, which consists of a lavalier mic, a UTX-B2 wireless body pack, and a URX-P2 diversity tuner. The plug from the lavalier mic is a 3.5mm TRS (stereo) connector that (obviously) plugs into the UTX-B2 audio input connector.
There are occasions where I would like to ditch the lavaliers and instead use a standard dynamic or battery powered condenser microphone and route its XLR outputs to the input connector for the UTX-B2. In the manual that I have for the system, under the section discussing the Audio Input connector for the UTX-B2, it says (literally):
"By using a commercially available XLR-BMP conversion input cable, UTX-B2, the line output connector of the audio mixer or the microphone which does not require the external power supply can also be connected"
Furthermore, there is another note that says
"When the MIC/LINE input selector is set to MIC position, a power voltage for the supplied lavalier microphone is applied to the audio input connector. For this purpose, a special electrical wiring is used inside this connector. Be sure to use a commercially available XLR-BMP conversion input cable to connect the equipment other than the suppled lavalier microphone."
Hmm, we have a bit of strange translation going on in these quotes, but what I think it is telling me is that by using an XLR-BMP cable, I can connect a standard XLR microphone output to the body pack in lieu of the Sony supplied lavalier, or another non-Sony branded lavalier. Is my assumption correct here?
I have done a search for the referenced cable and have found Sony part # K-1334 BMP/XLR conversion cable, listed for $66 USD, and the only site that I have found that seems to carry it is Expandore.net, which is in Singapore. This is a bit on the expensive side, as far as I am concerned; is this a Sony-only part, or is there an alternative that can be used? Or is it possible to make one of these up? I don't have any issue with doing so, if I knew what the wiring should be. Does anyone have any idea about this?
Also, I am a bit confused when reading the specs on various microphones and lavs, they typically quote such things as Open Circuit Sensitivity, maximum SPL and impedance, whereas the specifications for the audio input level for the body pack only quotes "-60dBV (at 0 dB attenuation level)". What must I look for in the specifications of 3rd party lavs and microphones to match this input level?
I hope that my questions aren't too inane or nooby, but I would like to better understand this stuff! Thanks for your input in advance.
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03-12-2009 06:43 PM
- Join Date
- Dec 2008
03-12-2009 08:22 PM
Long story short: the transmitter pack does send out a low-level voltage to power lav mics, which should be compatible with any third-party lavaliere (which you should look into very soon... Countryman EMW or B6, Sanken COS11).
This voltage output can interfere with the audio, creating noise, when sent to devices that do not need it (mixers, dynamic mics, battery-powered condensers) and can even damage certain pieces of gear. Mostly, it's a noise issue. So the adapter cable is wired to defeat this voltage for use with mixers and XLR-connected mics.
As for the other concerns on specs, here's what you need to know for now:
Mic level sources are roughly -60dBv. The "v" means that the decibel rating is voltage... the measure of the actual electrical signal. Audio input of -60dBv at 0dB attenuation means that, as long as the attenuation has not been activated in the menu, a standard mic-level signal should be nominal and will not overmodulate. A stronger source (powered mic... lavaliere using the transmitter's power supply or an XLR mic that's battery-powered) might need a little attenuation to keep it where it needs to be.
SPL is a rating of Sound Pressure Level, or the measure of the sound waves that travel through the air. Because the transmitter is all electronic and does not respond to sound pressure waves, it has no SPL rating. A mic, however, receives sound pressure waves and converts them to the electronic signal. Every mic has a maximum SPL (acoustic "volume," if you will) that it can handle before it starts to overmodulate (fancy word for "distort").
The decibel (dB) has no actual value in and of itself. It is used to quanitfy a signal in relation to a given reference point.
You will see other dB scales as you work:
dBV, which rates the signal's voltage relative to 1 volt.
dBv (aka dBu), which rates the signal's voltage relative to 0.775 volts. Mostly, you'll see dBu because the "V" and "v" can be easily confused.
dBm, which rates the load of the signal at 600Ohms in relation to 1 milliwatt.
Most dB scales use 0dB as their given reference, so anything lower than that is rated as a negative dB (such as -10dB), and everything above it is positive (such as +4dB).
The exception to that is dBFS, which is the digital scale. "FS" means Full Scale, because digital has an absolute "brick-wall" maximum. 0dB is this maximum, so reference points are set lower in order to give headroom for working with the signal.
In case that isn't confusing enough, there are other dBv ratings you should know:
-60dBv is mic-level, though some mics are "hotter" either because they are more efficient with creating the signal or because they have an external power source (typically, phantom power).
"Consumer" or unbalanced line-level sources (using RCA connectors or 1/4" tip-sleeve, or XLR if wired for stereo) run at -10dBv.
"Professional" or balanced line-level sources (using XLR or 1/4" tip-ring-sleeve) run at +4dBv.
It is very important to match your output dBv to your input dBv in the signal chain. If you pipe a +4dBv signal, or a -10dBv signal, into a -60dBv input (aka, line-level source to a mic-level in), you will get massive overmodulation and can even damage the circuits.
Pre-amps are always used with microphones, whether they're in a mixer or in a digital audio recorder or in the camera. There is no such thing as mic-level recording. Sound signals are always line-level when they hit the tape (or the hard drive or the SD card...). A pre-amp's job is to raise mic-level sources to line-level for proper recording.
No matter the voltage rating (dBv), 0dB is still your analog reference point when calibrating signal level on a mixer or to an analog recorder. -12dBFS is the reference point for miniDV, DVCAM, DAT, and most other digital recorders. But, -20dBFS is the reference for some digital media such as Digital Beta.
Hope this hasn't confused you.
Last edited by Alex H.; 03-12-2009 at 08:32 PM.Formerly known as C2V
Nobody notices audio... until it's not there.
03-12-2009 10:37 PM
- Join Date
- Dec 2008
Wow! Thanks for the information, it will take me a bit to digest some of this; I did previously understand some of the specs like SPL and such, but the information you provided on matching up mics to inputs is very helpful.
BTW, I found this Sony K1324 Mini-BMP Mic Connector that I think is what I will need to connect an XLR to the bodypack. The product listing says "Solderable BMP plug (1/8" stereo mini) for wiring of third-party microphones with Sony UWP series body-pack transmitter. Includes wiring schematic." I think is just the ticket for what I will need.
03-13-2009 08:23 AM
- Join Date
- Dec 2008
Thanks to a post on "the other" forum, I was pointed to the following, that seems to be what I am looking for:
EC15BX UWP 3-Pole locking mini plug to XLR (Female) cable