Released in 1980, the Boss BF-2 is the sound you hear in your head when you think "flanger." The original Made-in-Japan units sound fantastic, and the classic circuit is capable of a little wiggle to wild airplane whooshes and everywhere in between.
The flanging effect is produced by combining the original signal with an electronically delayed signal. Using four controls, the Boss BF-2 lets you dial in a variety of flanging sounds—from dynamic jet-plane effects to short delay, chorus, and vibrato sounds. "Manual" controls the delay time applied to the effect. "Depth controls the amplitude of the modulation, i.e. the size of the range in which the effect sweeps. "Rate" is straightforward: it controls the speed of the LFO wave that controls the effect. And "Res" sets the amount of effected signal fed back into the effect, so higher settings deliver a stronger effect.
This BF-2 was made in Japan, and its serial number (#33720) dates to 1983. It shows some paint chips around the edges (see photos), but it functions 100% as it should. The thumb screw for the battery compartment looks to be a replacement—just too clean relative to the rest of the pedal.
This '83 BF-2 produces authentic analog flange sounds. The hype is well deserved! Modern pedals don't come anywhere close these MIJ originals.