If another member doesn't respond I suggest either contacting Jonathan Halpern, US Distributor, or Goldprint Audio, Taylor is a LM dealer (also an Audiogon member - goldprintaudio) to see if one of them can help you out
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I emailed Jonathan Halpern from Tone Imports and Charlie Schnyder from Stereo Haven and they both promptly replied within an hour or two and they both said the same thing.
Apparently the knobs in the front are for fine tuning and not of much importance. The bias is adjusted mainly by the screws on the top for each tube. As long as the needles rest on the middle dot for each tube everything is ok.
This has been bugging me ever since I got the amp and I even emailed Line Magnetic in China and still the reply I got was far from useful.
These two guys put my mind at rest. Can't thank them enough!
" wow line magnetic doesn’t supply a manual with proper instructions on how to set tube biasing?! that brand is supposed to be cream of the crop "
I don’t know what the story is with the manual that came with the LM amp in question, but the manual that came with my LM 518IA (845 tubes) was straightforward in words and pictures as to how to bias it.
I found you the manual online for the 845 Premium; link is below. The bias instructions are on page 9 and are straightforward.
I might be wrong but reading the manual I think that what the front knobs do is allow you to monitor the bias of each tube via the bias meter next to them . You can probably double check that with Jonathan.
On the 518 there’s a small toggle type lever next to each 845 tube that when moved shows the bias on the front meter, If the 845 premium doesn’t have them then checking the bias may be as I note above