[ravi28UK]

Hi Guys,

I just purchased a Sipura SPA-841 off ebay and configured it to use voipstunt and sipgate sip accounts. Both sip accounts register fine and i am able to make and receive calls. The problem i am having is a constant hissing sound in the background at the other persons end .. other party also says their own voice constantly echo's ?? I can hear them crystal clear at my end.

If I push the up says 75% up on my phone.. I can hear the hissing sound at my end and but my voice echo's really bad!. However the other party can now hear me ok with no hissing sound!!? There is still a echo sometimes..

I am using the G711u codec and Silence Supp Enable is on disabled.. I have also changed RTP Packet Size: to 0.020 but same problem.

My phone is well away from any computers or routers.

I have 2mb broadband connection with 256k upload speed.

I also have a cheap usb phone which i use with my wifi laptop and voipstunt phone software and xlite for sipgate. I get crystal clear sound most of the time.. without any interfence or hissing sound or echo! 90% of the time most people think i'm calling off standard pstn line.

I am really disappointed.. I thought a £80 voip phone would work fine and much better then £10 usb phone!! I just hate been constantly infront my laptop, if i need to make a call...

I read somewhere this might be a hardware fault that can be simply fixed my opening phone and moving speaker or wiring .. but i can rember or find the website link.

Anybody got any ideas on how to resolve this problem?

Thanks..

Ravi :roll:

[ravi28UK]

I have the latest firmware on the phone = 3.1.4(a) and hardware version = 1.0.0(198a) ..

I am also using a linksys WRT54G with DD-WRT V23 VOIP..

I have also tried plugging the phone directly into my broadband modem (bypassing the router) but the same problems with hissing sound and echo.

[mberlant]

Gentlemen,

You will need to adjust the gain settings on your respective phones to balance voice level against echo and hiss at the receiving end of the particular gain setting. It seems that you both have transmit gain setting that are too "hot" and need to be reduced (moved towards a smaller positive or larger negative number). Reduce the gain 0.1dB at a time until the echo is reduced or eliminated and the voice level is still acceptable.

[atheling]

My SPA-841 was delivered with version 3.1.3a firmware which exhibited a low level "AGC pumping" sound when there was silence and, worse, clipped the first syllable after a silent period. Reading the release notes for 3.1.4a one of the improvements was: "Improved handset and headset input gain dynamic adjustment"

So I updated the firmware (long story omitted there, punch line is the phone requests the file from the TFTP server with a leading "/" prepended to the name).

The 3.1.4a firmware exhibits much higher voice and noise (hiss) levels than the 3.1.3a firmware. My workaround so far is to reduce the handset gain (I don't have a headphone nor do I use speakerphone for much else than checking voicemail).

However all I see for gain adjustment under the admin/advanced page is in the "Phone" tab. There are three choices in the pulldown: +6, 0 and -6. I had to set it to -6 to get the hiss to be acceptable. I am told my voice is now low but still understandable.

I'd love to see how to adjust the gain to something like -3, but don't see the control for it. On the SPA3000 (which has issues of its own, I do have that type of control).

If you would like to try v3.1.3a firmware, it is available on the Sipura web site. Just look at the link for the current v3.1.4a firmware download and use the same URL but with the name editted for 3.1.3a.

For what it is worth, my hunch based on decades of writing firmware for embedded products is that the SPA-841 has a poor design in the analog section of the hardware that results in a low S/N for the microphone of the handset. I think they tried to fix the hardware through some sophisticated software (v3.1.3a) and ended up with issues so then backed out firmware the AGC/VAD with v3.1.4b to end up with what they have now.