Re: R1556A High imp. phones
Intriguing: though I can't provide an answer to your query, the 'modifications' to your AR88 front panel match up with a couple of unexplained bunged-up-holes in the front-panel of my AR88.
[they're filled with rather accurately machined plugs on mine - kinda like someone wanted to reverse the modification?]
--G6Tanuki
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