If you get the "Sorry, the file cannot be displayed. There seems to be a technical issue ..." error when trying to view an image, a workaround is to click on the cog icon in the upper right side of the media viewer, and then select "Disable Media Viewer". We are aware of the problem and are looking for a solution.
The probes contain sampling gates but not amplifiers. The front-end amplifier is in the 4S3 and is composed of a 7308 tube (premium 6DJ8) with its two triodes connected in a common-cathode cascode topology.