Did yours actually have 'Plus' printed on? If not, I wonder if some late originals were made available in the black finish.
I was present at the local dealership the day their first Alpha amp arrived in all of its grey/black glory. None of us present were all that impressed when the lid came off, however, we were all quite pleased with the sound. I was there to take home a minty NAIT trade-in for the weekend; never took that amp back.
I'm not sure it is written "Plus" somewhere.
This is a comment from John Dawson (Arcam) on Google Groups:
It is the original Arcam Alpha amplifier - launched IIRC at the end of
1984 and probably made sometime in 1985.
The idea was to make something that could sell at about
60 - 65 % of the price of our best selling A60 - i.e. £120 rather than
£180 - £200 (it is too long ago for me to remember the details
exactly).
It was our first heavy use of industrial design - the work was done by
Peter Harries of Cambridge Industrial Design. The case was all
aluminium apart from the moulded front panel.
The power IIRC was 30 WPC into 8 ohms with a complementary bipolar
power amp. To save cost it had a frame transformer, which did colour
the sound slightly for the worse. People either loved or hated the
grey front panel.
It sold OK but did not really hit the spot. In 1986 we launched the
Alpha Plus, with a toroidal transformer and a black painted front
(using the same moulding - the tooling had been very expensive). It
was £10 more and sold at a 50% higher rate.
A couple of years later we retooled it to 430 mm wide (the earlier
models were 400mm - don't ask why!), called it the Alpha 2 and put the
price up £20. It sold 50% more again.
There is a lesson in there somewhere!
You can maybe get a spec from our support staff at
[email protected]
Probably easiest to give them a mail address, though they may have a
PDF.
HTH.
John Dawson (Arcam)
Summarizing:
A&R Alpha Serial numbers 1 - 5580 (grey - frame transformer - 400mm wide)
A&R Alpha Plus Serial numbers 5581 - 18799 (black - toroidal transformer - 400mm wide)
Arcam Alpha 2 Serial numbers 18800 - 39649 (black - toroidal transformer - 430mm wide)
Arcam Alpha 3 Serial numbers 39650 -
Serial number chronology comes from Radiomuseum.