Asterisk 1.8 OSS problem with quiet sound

Hello, currently I’m running Asterisk 1.8 on Banana Pro with Raspbian. In Asterisk I’m using chan_oss and usb sound card, but normally in linux system ALSA. I managed to set up two-way communication between server/clients and clients/server, it means I can make calls from Asterisk console to client/multiple clients and from client to console.
I can speak and hear voice,but it is really quiet on client and console side (also there is much other noise). Have any of you got similar issue with OSS in Asterisk? Could adding amplifier solve the problem?