To be honest those amps (two mono amps) don't get used every day.
The filament alone is 10 volts at 10 amps, so that is 100 watts.
To get back on topic, you will be able to watch these BBC Wales programmes on BBC i player.
Here is part 2 of the series.
http://www.bbc.co.uk/iplayer/episode..._Ahead_Part_2/