Rocket Current Draw

[passfan]

I'm adding up the current draw for the rocket because I'm trying to build one with what I have on hand and later on upgrade into the proper iron. So if I have it right each output tube is roughly 25 ma and each preamp tube is around 3 ma worst case. That would draw around 110 ma from the transformers main winding. Am I missing something ?
I'm planning on starting out with a 2 tube rocket, with holes to add the other tubes later, and a 125 ma PT. I don't want to grossly overload the PT but I realize it may get warm and I can live with that until such time as I can get new iron.

[FYL]

EL84's draw 45 mA plate + 10 mA screen max in a typical Rocket-class amp, so a PPP with 4x output tubes and 3x ECC83's should be rated for 200 mA minimum (the amp is class AB, with only two EL84's drawing current above idle).

Your 125 mA PT should be OK for a PP version (two EL84's).

[passfan]

EL84's draw 45 mA plate + 10 mA screen max in a typical Rocket-class amp, so a PPP with 4x output tubes and 3x ECC83's should be rated for 200 mA minimum (the amp is class AB, with only two EL84's drawing current above idle).

Your 125 mA PT should be OK for a PP version (two EL84's).

At this current, given a 12 watt plate dissipitation , the voltage would have to be 200 volts or less on the plate. Is this right ? Is 45 ma for one tube or a pair of tubes ?

[FYL]

At this current, given a 12 watt plate dissipitation , the voltage would have to be 200 volts or less on the plate. Is this right ?

Dynamic <> static.

A typical Rocket shows app. 290V plate V and slightly less screen V. Max instantaneous plate dissipation is app. 290 * .045 = 13 W. This is a dynamic value, unless the amp is maxed at all time.

Max plate dissipation is a design center value for continuous operation, not an absolute max, so the EL84 is run hot as it should be, but well into specs. Idle - the static part - is app. 10W, well into specs again.

Is 45 ma for one tube or a pair of tubes ?

One tube. And don't forget screen current: those little buggers can easily suck 10 mA when pushed real hard.

Check page 4 of the datasheet for class AB PP operation @300V plate: http://www.mif.pg.gda.pl/homepages/fran ... e/EL84.pdf

[passfan]

Thanks for the help and the advice.

[2tone]

a 4 TUBE el 84 IN CATHODE BIAS should have a 300 ma power tranny. It will run cooler. Old AC 30's and early matchless had 160 ma ratings, and ran very hot ( too hot for me!)..