Hi Everyone, I wanted to share some information on using these regulators in high gain / low noise tube circuits. It should apply to any circuit though. I have found that the basic schematics for the LR8XX do not always show the use of a capacitor between the adjust terminal and ground. I have found that this component is extremely important to keep the noise level down in the output circuit. Using a 1.0uf poly will reduce the noise in something like a preamp by several db. In one case about 8! This capacitor needs to be rated for the output voltage. It is in addition to the one on the output terminal that is there to prevent oscillation. I normally use a 1 uf there as well. If the distance to the point of use of the regulated voltage is under say 3 inches you can put the cap at the point of use (often a tube socket pin). Bigger capacitors on the output are fine but anything over 1uf on the adjust is unnecessary.
More info: The Care and Feeding of LM317 and LR8 Integrated Circuit Regulators, Particularly in Valve Circuits