[asterisk-users] Digium Zaptel volume issues

[Rich Adamson]

Charles K Green wrote:
> All,
> 
> Anyone have any experience with the Digium TDM400P?
> 
> We have a Digium TDM400P up and working with asterisk. We've fxotune'd the
> interface and pretty much eliminated all of the echo on the channel. 
> 
> Our latest issue is that all calls that run over the zap channels sound
> muffled and distant. I upped the rx gain and that helped some on the inbound
> voice but now we have some static creeping in. If I up the transmit gain, we
> start to get more echo so I'm really hesitant to do that too much.

Lots of experience with it.

I recently learned that a fixed loss is statically defined in the 
drivers for the card. The loss has been there since the card first came 
out and it is supposedly required to make the s/w EC function.

The low audio issue is a common problem for all users, but it becomes 
far more noticeable for those that use the card on long pstn analog 
loops.  In other words, the greater the pstn loss, the lower the audio 
level, and increasing rxgain/txgain cannot be used to compensate for it.

No fix or workaround.