A radial engineering X amp driver box. I used this for sending out tape-recorded vocal tracks through old guitar amps. It works great, merely don't utilize it much anymore. The one I have is a more mature version. The new one that Radial has is a yellow box. On the radial internet site it states there is no distinction between the 2 aside from that they transformed the color so it wouldn't get wronged for the J48 direct box. Below's a web link for additional details
http://www.radialeng.com/xamp.php