My Spendor BC1As are a piece of HiFi history, but the built in amplifier is not without its inconveniences. The M.208 amplifier is OK but nothing special, and certainly no better than my main amplifier (Cambridge Audio A1). It also has a bit of a hum. But mostly it's just inconvenient to hook the speakers up to the rest of my system - it will be far easier if I can bypass the amp and connect straight to the crossover.
But, I don't want to chop these speakers about too much. Whatever I do needs to be reversible.
A switched Speakon socket would have been ideal - it could switch out the M.208 amp when external speaker cables are connected. The only place to fit it without making a new hole is in place of that rectangular 4-pin Painton connector, but the hole is too small, so that's not going to work.
I was lucky enough to find the right kind of connector for sale on ebay. These are Plessey Painton connectors (called Jones connectors in the US, although I think there are some differences) which were typically used in industrial and military type applications. I think they came on the scene in the 40's, or maybe late 30's, although the Painton company was bought by the Plessey company at the end of the 60's. It makes sense that the sockets on the M.208 amp come from around this sort of time as the BC1's hail from the late 60's/early 70's. They have fairly chunky metal contacts, rated for around 10A I believe. Should be fine for the relatively low wattage these speakers can handle.
These are the connections inside the speaker before - The crossover is connected to the amp with the (rather weedy) orange and black wires. The Painton connector is paralleled with the other balanced line input jack, feeding the amp.
And afterwards... The crossover is soldered to two of the Painton pins, the amp to the other two. If I want to use the internal amp in the future I have the option to bridge the contacts between amp and crossover externally on the plug. The redundant shielded input cable is taped up and tied out of the way.
I used spade connectors on the speaker wires for now, which just about fit on the lugs of the Painton plug. Soldering would probably be better but this gives me the option to reconfigure the plug if I want to use the internal amp.
With the speakers now passive, they can be connected up to the rest of the system.
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