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Old 23rd May 2009, 02:51 AM   #1
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Default microphone levels

I was attempting to connect this microphone to my computer:
http://www.amazon.com/Technica-ATR-5...3043084&sr=8-1

with the recording settings set near max, and the "tele" setting on the mic, I get mainly noise, but can record voice at distances up to 1ft.

I had hoped for more then 1ft. the "normal" setting cannot even pick up voice at 1ft.

this is pointing the mic directly at myself.

is this normal? do camera's just have amazing noise-reducing high-gain stages?
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Old 23rd May 2009, 02:15 PM   #2
Ron E is offline Ron E  United States
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I see a battery, so it is possible the mic is meant for the line input, or perhaps it requires a preamp. Computer mic inputs supply 5V power and are generally very noisy. Try the line input first, and doublecheck your mixer settings.
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Old 24th May 2009, 12:01 AM   #3
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from the testing with audacity, I certainly need at least 40dB of gain if not more. this is with the line input, which is quiet, but again, very low volume. i'd like to be able to use this mic at about 2m distances. currently, its barely audible at 0.25m.
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Old 24th May 2009, 12:14 AM   #4
Westerp is offline Westerp  Netherlands
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Somewhere on the Interweb:

Quote:
Generally all PC soundcards have microphone input. Soundcard mic inputs are generally pretty crappy, meaning usually that they are noisy and frequency response leaves much to be desired. Soundcard microphone inputs are usually optimized only for telephone type voice applications, not for any serious music recording. The microphone input in soundcard is generally designed to be used only with a "computer microphone" in mind. This category means those cheap computer microphones you get sometimes with the computer and can buy from the computer shop. This it to what use they are designed for. And if you get this kind of microphone it will work practically with any normal soundcard. If you connect some other microphone type, then your resuls vary from card model to another (some can take other microphone types better than some other). Sound Blaster soundcards (SB16,AWE32,SB32,AWE64,Live) from Creative Labs use 3.5 mm stereo jack for the electret microphones. The microphone connector uses he following wiring pinout:

3.5 mm soundcard microphone input connector

The 5V voltage on the connector is heavily current limited (typically goes through around 2.2 kohm on soundcard). Depending on the card the voltage might not be exactly 5V (usually something between 3 and 5V when no microphone is connected). Practically all other soundcard makers have copied this pinout and connection idea to their soundcards. The circuit idea used in the soundcards microphone inputs is the following:

Sound Blaster mic input circuit

There has also been standardizing work going on this connector also. For example PC99 standard mentions the PC soundcard microphone interface details: Three-conductor 1/8 inch (3.5 mm) tip/ring/sleeve microphone jack where the mic signal is on the tip, bias is on the ring, and the sleeve is grounded. This design is optimized for electret microphones with three-conductor plugs, but will also support dynamic microphones with two-conductor (ring and sleeve shorted together) plugs. Minimum AC input impedance between tip and ground: minimum, 4 kOhm; recommended 10 kOhm. Input voltages of 10.100 mV deliver full-scale digital input, using software-programmable .20 dB gain for low output microphones.Bias should be less than 5.5V when no input and at least 2V with 0.8mA load. Minimum bias impedance between bias voltage source and ring: 2 kOhm. AC-coupled tip to implement analog (external to ADC) 3 dB rolloffs at 60 Hz and 15 kHz.

Most sound card inputs require a minimum signal level of at least 10 millivolts. Sound Blasters and some older 8-bit cards need 100 millivolts. Practically all consumer soundcard supply bias voltage on their outputs to power the electret microphones (the only microphone type which works with this kind of cards). The input impedance of the typical PC soundcard microphone input is typically in order of 1500 to 20000 ohms (can vary from card to card).

This discrepancy means that if a typical professional microphone is connected to a sound card input, the user will have to shout into the microphone or hold it just an inch or so away (or both) in order to produce a strong enough signal for the sound card to "hear." Other problem with dynamic professional microphones is that dynamic microphones do not like DC current, but soundcards have 1-5V power supply for feeding Electret mics on the 3.5mm-jack?s ring, which can touch the tip of the connector when you plug your microphone in and if you are unlycky it can damage your microphone.

There are two possible solutions for the low volume problem with professional microphones connected to soundcard. First option is to try to increase the sensitivity of the sound card input with the control software which come with the soundcard (audio mixer application or such). This might more or less help depending on soundcard used. If the input sensitivity cannot be increased eough, another option is to amplify the microphone signal before it goes into the sound card input. This can be done by running the microphone signal through a device called a mic preamplifier or mic-to-line amplifier and feed that signal to the line level input in the soundcard (this approach usually gives better sound quality also).

Note for serious audio recorders: Soundcards with mic inputs on minijacks are usually low-quality devices, which means that they are not suitable for high quality recording of audio (they are still OK for general multimedia use or internet telephony). Such sound cards are not designed for high quality recording. Get a real soundcard and use a real audio application if you want quality results. If you want to get really good quality microphone recording using computer the microphone wiring should be balanced and the microphone preamplifier should be external to the computer casing. Usually you get quite acceptable results by using an external microphone preamplifier that is connected to line input in the soundcard. Genrally for a home recorder, I can recommend a small decent quality mixing board connected to soundcard line input. With such mixer between microphone and soundcard, you will get good results and have freedom to select practically any microphone you want (anything you can connect to that mixer).
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Old 24th May 2009, 12:41 AM   #5
cuibono is offline cuibono  United States
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I wonder if your microphone is trs and the mic input is ts, or trs wired in an unusual way, causing cancellation of the mic signal?
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Old 24th May 2009, 08:37 AM   #6
Westerp is offline Westerp  Netherlands
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The simple version:

Quote:
Signal Level
Professional microphones put out a very weak signal - less than 1/1000th of a volt, or 1
millivolt. Audio inputs on sound cards, even though they may be labeled "Mic In" or be
identified by a small microphone-shaped icon, often are not designed to accept such a
low signal level. Most sound card inputs require a minimum signal level of at least 1/100th
of a volt (10 millivolts); some older 8-bit cards need 1/10th of a volt (100 millivolts). This
discrepancy means that if a typical professional microphone is connected to a sound card
input, the user will have to shout into the microphone or hold it just an inch or so away
(or both) in order to produce a strong enough signal for the sound card to "hear."


ATR55 Cardioid Condenser Shotgun Microphone
Designed especially for use with video cameras.
Quote:
OPEN CIRCUIT SENSITIVITY
"Normal": -56 dBm, 1 kHz at 1 Pa
"Tele": -45 dBm, 1 kHz at 1 Pa


http://www.sengpielaudio.com/calculator-db-volt.htm
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