The C 451 was a long running condenser modular system with a variety of different capsules and accessories. The most common is the CK1 cardioid capsule, which has a bright, detailed sound that makes it a popular choice on acoustic guitars. We also have a pair of CK22 omni capsules, but several other options were available. AKG also sold accessories like attenuation pads, extension tubes, and swivel joint. The C 451 preamp saw a few changes over the decades; the 451 EB added a two position high-pass filter, and later the 452 EB was released and runs exclusively on 48V phantom power while the other bodies can operate on 9V-52V phantom.