Linear Tube Audio UL+ Instructions Manual page 11

Changing tubes:
17JN6: The power tubes are self-biasing and do not need to be
matched for gain.
12AX7: The 12AX7s should be a matched pair.
12AU7: These are used in the preamp section (the smaller, vertical
circuit board) and in the power amp section. In both cases, the
12AU7s should be matched pairs and each individual tube should
have both of its triode sections matched as well.
The sockets are tight, so gently rock the tube pins until you are
able to remove the tubes. We use high-quality ceramic tube
sockets with gold pins which are designed in such a way that the
white ceramic part may shift slightly. This is an intentional design;
the tube socket is very secure.
Given the tightness of the 12-pin tube sockets, the relatively small
selection of 17JN6 tubes available, and the high quality of the
tubes we supply with the amplifier, we do not recommend
changing the 17JN6s.
Before changing tubes, turn off the amplifier and wait at least 10
minutes to allow the stored power to discharge. Avoid touching
any of the components on the circuit board, especially the
vertical circuit boards.
Fuses: The ULi+ has two fuses on the power board and two fuses in
the IEC assembly, located on the back panel. The fuses on the
power board are one 5x20mm, 4A, slow-blow fuse and one
5x20mm, 2.5A, fast-blow fuse. In the IEC assembly, there are two
5x20mm, 4A, slow-blow fuses.
For more information and FAQs, please visit
www.lineartubeaudio.com or contact us at
hifi@lineartubeaudio.com.