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Well, I can tell thee ONE thing? It ain't fookin 'Class A'!
Dave.
You can get 100W per pair of EL34 running them at their voltage limits into the correct load.
I've measured over 90W from a pair of EL34s in a Dynachord amp with around 800 VDC on the anode.
In fact, there used to be a Velleman kit hi-fi power amp which Maplins used to sell, which when I looked at the schematic was basically an Orange! Although they only claimed 90W per channel.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
The HT-60 Stage can easily hit 75/80 W at just visible clipping.
Dave.
Seriously: If you value it, take/fetch it yourself
Mullard EL34 datasheet (pg3) shows 100w @ 5% THD possible from a pair of EL34s with 800v in anodes, 400v on screens (separate supply), and an 11k Ra-a load.
Anode dissipation at idle is only 20w (800v x 0.025A), or 80%.
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
This is dissipation in the valve NOT the load.
In a power amp, power is dissipated in both the valves and the load.
Any dissipation in the valve is wasted; a 100% efficient amp would dissipate no power in the output devices at all and power would only be dissipated in the load.
Of course no amp is 100% efficient (although class D amps can acheive over 90% efficiency), so there is always power dissipated in the output devices as well as the load.
The most inefficient way of running the output valves is in class A, where for maximum power the valves would be biased at their dissipation limit (25W) and with a theoretical 50% efficiency for push pull class A (ie only 50% of the power going into the power amp is dissipated in the load) you would get a theroertical maximum 25W output power per pair of valves (ie each valve would supply 50% of 25W). In parctice efficiency is usually nearer 40%.
Biasing the amp into class B loading, then output devices dissipated virtually no power at idle, and only conduct for half the wave form, so power dissipation in the output devices is greatly reduced, thus you can get more power delivered to the load whilst still keeping the valves within their dissipation limits.
Calculating maximum power dissipation in class B amps is more complex as the power dissipation in the valves occurs at about 25%-50% of maximum output power, however it should be obviousl that a more efficient amp can deliver more power to the load without exceeding maximum dissipation, thus you can generate 140W of power from a pair of EL34s without exceed in dissipation limit of the valves.