[asterisk-users] Noise on FXS ports (Sangoma)

[Stephen Bosch]

shadowym wrote:
> All I know is that your rx gain, at 0db is probably way too low.  My tx gain
> is typically set to -3db.

I set it 10 as per your previous post and ended up with audio so loud
there was clipping and distortion. I don't think that's the cause.

Sangoma has expressly told me to *increase* the txgain and leave the
rxgain alone.

Don't get me wrong -- I appreciate the help -- but I think we're barking
up the wrong tree here.

> Yes, I was thinking sip phones when I made the
> amplifier comment.  If you hear the noise as soon as you take the analog
> phone off hook without dialing the PSTN then I don't see how it could have
> anything to do with the telco card.

But that's just it -- I wasn't referring to the telco card. I was
referring to the FXS module which is providing dial tone to internal
analog phones. They're the only devices that exhibit the noise.

Do these gain settings have any impact on FXS modules in the first place?

> Is it a feedback type noise or
> background hiss?  Feedback type buzz would lead me to believe it's ground
> loop as someone else mentioned.  Ground loop hum is a PITA to try deal with.

No, it's like a background hiss. I have a recording of it if you're
interested in hearing it.

-Stephen-