[asterisk-users] [headset/mic] Volume too low + echo in *

[Dave Platt]

> 	I'm having the following problem when using a headset on XP
> connected to an on-board Realtek soundcard on an AsusTek M2N68-AM Plus
> motherboard:
> 
> - Using any sound recorder (Windows', Audacity, XLite), the level is
> just too low when speaking at a conversational level, even with the
> microphone level pumped all the way up (line displayed totally flat in
> Recorder)
> http://img704.imageshack.us/img704/7981/headsetlowvolumeecho.jpg
> 
> - In addition, when making a call with XLite and Asterisk, I get a bit
> of echo
> 
> - Same issues when trying with a different headset

Same headset model, or different headset model?

> 
> - Enabling "Auto gain control AGC" in XLite makes no difference.
> 
> Any idea what can be done? Should I use a different soundcard?
> Amplified headset? 

Most computer mic inputs these days, are designed to work with
mics and headsets using electret microphone elements.  These
microphone elements normally have a built-in FET buffer/amplifier,
and have a respectably high audio output level.  The FET amplifier
requires some DC power to operate;  this is normally provided by
the sound card, as a resistor-coupled DC voltage applied to the
mic input pin inside the jack (it's usually in the 3-9 volt range).

Some headsets use "dynamic" (electromagnetic) microphones...
essentially little loudspeakers operated in reverse.  These do not
require DC power from the sound card to operate, but they have a
significantly lower audio output level.  They do require
amplification in order to drive an input designed for electret
microphones.

Some sound cards have mic inputs which are switchable... the
DC power feature can be enabled or disabled, and there's a
"gain boost" setting which switches in a preamplifier stage
(often around 10-20 dB) for use with a dynamic mic.

You may be attempting to use a headset with a dynamic mic,
with a sound card whose mic input was intended only for use with
electret mics and doesn't have a preamplifier.  If this is the
case, switching to a headset with an electret mic and its built-in
FET buffer-amp would probably be your easiest solution.  If that's
what you mean when you refer to an "amplified headset", then yes,
that's probably what you should do.  You wouldn't need a headset
with a separate amplifier-box... the FET amplifier is usually
build right into the microphone element.

It's also possible you have a bad PC sound interface... try
using a different PC with the same headset(s) and see if the
problem persists.

You can probably buy or build a preamp for your existing headset
(I recently built one for a similar purpose) but considering
how inexpensive "A/V" comm/gaming headsets are these days
it's certainly cheaper to buy one.

Another option would be to buy a USB-connected headset...
these have all of the necessary gain electronics in them,
as well as a "USB sound card" chip.  There's only one plug
to plug in, and (once the necessary USB sound drivers are
installed) you could be confident of having the same sound
level and quality on any PC into which you plug it.

>        Can something be done in Asterisk about the echo?

How quickly after you speak, do you hear the echo?  Is it
near-instantaneous, or significantly delayed?  What's your
outgoing voice connection (SIP, IAX, or an actual hardwired
phone line with some sort of terminal adapter)?

Does the caller at the far end hear an echo from what s/he
says?  Or does the echo affect only you?