Connect it straight to a speaker, and the 6 LED's will correspond to the signal volume.
Detail:
" This is super V.U. circuit that is specially designed for connecting
directly to speaker without power
supply.
" It can be used as other stardard
V.U. kits but this one is much lower cost.
" Its LEDs will display one by one
according to signal volume, and not all at once.
" Easy application, durable and can be used with 10 - 30 Watt amplifier kits.
" Recommended housing : FB12
" PCB dimensions : 2.0" X 1.0"