From: Mic Miller <miclist@em...> - 2008-05-14 21:05:16
I am using an Audiostix 2 attached to a Connex400.
The UCB1400 datasheet indicates that there is a 20 dB boost (see LNA
gain below) available for microphone recordings. Is this available?
Some versions of alsamixer have a 20 dB "mic boost" but I don't see it
on the gumstix.
Also, the microphone appears to be powered (active microphone) although
it is described as a "stereo line input". Does that happen when a
microphone is chosen as a capture device? Does it also connect the
ground side of the microphone to the MICGND pin as described below?
I'm looking for more signal gain although I don't rule out the need for
a better microphone. :-)
Excerpt from UCB1400 datasheet:
9.1.2 Microphone input
The UCB1400 audio codec input path accepts microphone signals via
a DC blocking capacitor. The ‘ground’ side of the microphone is either
connected to the analog ground (AVSS) or to the MICGND pin of the
UCB1400. The latter will decrease the current consumption of active
microphones, since the MICGND pin is made Hi-Z when the microphone input
is not selected (SL = LINE_IN_L in Record Select register (0x1A)).
The LNA gain can be set to 0 or 20 dB via the 20 dB bit in the MIC
Volume register (0x0E). Additional gain in 1.5 dB steps is possible via
the GL[3:0] in the Record Gain register (0x1C).
Thanks for any insights,