[Asterisk-Users] Zap tuning for echo/gain

[jerry at voiptower.com]

I'm having a bit of an issue with one of the bargain x100p clones, and
I'm not sure what the right approach is.

My symptom started as way loud offset delayed echo from voip hardphones -> PSTN
through the clone card. I played with and then learned everything I could about
echo cancelling, and have managed to bring the echo down to acceptible levels,
where it's not too intrusive.

In my travels I discovered "ztmonitor", and thought I'd run this. Now, with
no call and no activity on the line, the RX side shows a reading of about
1/3 of the bar graph. I figured this is bad (right?) and tweaked my rxgain
value (I had never had to touch this before) until ztmonitor only showed
one bar. I accomplished this by adding a negative value to the rxgain, I
believe it was -12.

My question is: Is this the right approach? Should I be tweaking my gains
first, and then adjusting echo, or vice versa? Is there something else
completely I should be looking at first, or is this the right thing to do?

I did have a genuine Digium analog TDM card in there previously, but I had
to swap boxes and for some reason the TDM isn't probing (and digium support
haven't been too helpful, but that is another story). The TDM didn't need
any tweaks; it seemed to have worked out of the box (although I might have
been more tolerant of slight echo before, but the clone card was simply
intolerable for conversation).

Any suggestions or comments welcome.

Thanks,
J.