These are three battery powered mic preamps. My grandfather built these in the late 70's and 80's for portable reel to reel tape recording of live performances. Made with battery power supplies to keep noise and hum out of the recordings. All these preamps are made with discrete components, they were, and are high quality.
The big beige colored one attached to the black battery pack is a preamp, mixer, mic in, line in, and line out. The small grey box on the left is a 2 channel mic preamp and you can see the specs in the pictures.
The big beige colored one attached to the black battery pack is a preamp, mixer, mic in, line in, and line out. The small grey box on the left is a 2 channel mic preamp and you can see the specs in the pictures.