The Tektronix 013-0146-00 provides a printed circuit board and connectors for non-permanent attachment of user-provided circuitry directly to the front of an AM501. It is described as:
The AM501 Auxiliary Circuit Board Kit attaches to the input and output terminals on the front of the AM501 Amplifier. The kit is a PC board has six terminal studs for attachment to the amplifier's banana jacks and is approximately 2.5-inches square. This permits the designer to build a circuit of resistors, capacitors, and other components for use in conjunction with the AM 501's input, output, or feedback circuits. With several boards, the AM 501 Op Amp circuit can be changed instantly in configuration from integrator to differentiator to amplifier.
An additional advantage of the kit is that it does not interfere with the other connectors on the face of the AM501.