X-don
Imported Account
Apr 17, 2001, 9:18 PM
Post #1 of 1
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GL-1 MIC Audio input details
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Thought I'd post some additional information about the mic input characteristics. These tests were using a steady state 1 kHz signal from a signal generator and do NOT represent how the GL-1 deals with transients. The output was measured from the .WAV files captured via IEEE-1394. I used 16-bit 48 kHz mode. The input level is measured at the MIC input terminals.
Channel balance on the unit I tested was within 0.25 dB.
For reference, the GL-1 specification is an input sensitivity of -55 dBV in MIC position and -35 dBV at MIC ATT setting. My measurements confirm this. Using a steady signal, an input signal of -35 dBV will result in nearly full AGC clamping of the signal, and provide about 4 dB of head room for transients. Similar results are obtained if the input is -55 dBV and and the MIC position is used.
Using the MIC ATT setting, gain is linear (a 3 dB increase in input yields a 3 dB increase in output) until the input reaches around -45 dBV. At this point there is about 12 dB headroom for transients - typical of consumer gear. As the steady state input signal starts to increase above -45 dBV, the AGC starts to reduce the gain. Increasing the steady state input signal beyond about 40 dBV results in almost no increase in recorded level, but it has cut into head room for transients.
As to distortion, second harmonic distortion is the dominant component, and it is more than 46 dB down until the input reaches about -20 dBV. At about -15 dBV input, the third harmonic becomes equal to the second harmonic, and at -12 dBV it is very audible. At -10 dBV input the third harmonic is down about 16 dB and very audible. Clipping (symmetrical) is obvious in the output wave form.
What does all the above mean? It means that the raw output form most soundboards or mixers will be too hot to connect directly to the GL-1 MIC input. In fact, in some mixers even selecting a mic level output may be too hot since they often are on the order of -30 dBV. If the above is greek, contact a soundperson for assistance.
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