DSN's masers are cooled with liquid helium to keep RF noise down. An amplified band of RF leaves the LNA and is directed to the receivers, which are shown in the next diagram. This represents the uplink signal to be amplified by the klystron, which is a microwave power amplifier vacuum tube. Polarization of the klystron's output is selected by a filter to match the spacecraft's receiver. The klystron's output illuminates the DSS's antenna reflector so it can be seen by the spacecraft.
Most klystrons have to be actively cooled by refrigerated water or other means.
Looking at the lower diagram, which represents equipment in the SPC, the signal from the LNA enters at the top. If two or more LNAs are operating, the path would be multiple. The switches in the diagram show there's an operational choice. The open-loop receivers select a band of frequencies to amplify for further processing by RS or VLBI equipment. VLBI equipment typically outputs data to tapes that are delivered to a correlator at a different location.