In article ,
Johnny B Good wrote:
On Wed, 23 Aug 2017 18:11:50 +0100, Dave Plowman (News) wrote:

In article ,
Johnny B Good wrote:
The advice note attached to those Quad 405s was simply a reminder
that the supply voltage would still remain 240v with very little
danger of the supply ever being matched to the notional 'Harmonised
Supply Voltage' of 230v.

I don't know the history, but it seems it was the only bit of BBC
equipment marked thus. The inference being they didn't take kindly to
being set to 230v.

One possibility might be Quad Acoustical taking advantage of the
tighter voltage tolerance required (for whatever reason) to save
transformer materials costs otherwise demanded by a "Universal" higher
primary voltage design supplying a voltage agnostic circuit (voltage
regulators and/or final output stage) in the form of extra iron and
copper to keep hysteresis losses at an acceptable level.

If you have to go to the trouble of closely matching a mains
transformer primary voltage to the supply voltage due to other
considerations such meeting a maximum output power for a given
acceptable level of distortion, you might as well extract the full
benefit of minimising transformer costs whilst you are at it. (i.e.
Don't miss a trick! :-)

The other possibility - it was the BBC active crossover fitted inside, and
powered from the same PS. A weird and wonderful device.

--
*If at first you don't succeed, avoid skydiving.*

Dave Plowman London SW
To e-mail, change noise into sound.