Power transformer strong enough for a small SE Tube Amp with 3 tubes ?

[Gokarna]

Hello to everyone outthere,

I'm planning to build a small guitar tube with an ECC83 and an EF86 (http://ordoalephysik.files.wordpress...hilips1970.pdf) in the preamp stage and single ended EL84 as poweramp.
The output transformer will be a Hammond 125 ASE.


My question is, if the power transformer (30 VA) I want to use is strong enough ?

On the secondaries, it has 1. 200V/ 0,1 A
and (heater) 2. 6,3V / 1,5 A.


Second part of my question, how do I have to calculate this by myself for further projects
(Which data of a tube datasheed is the important) ?

Maybe someone knows a link with a good and understandable explaination ?

Please excuse my clumsy english, I live in Germany and don't have much opportunity to talk english...

I'm looking forward for your answers,

best regards and thanks,


Till A

[txstrat]

Hello Till,

welcome to the forum.
Your transformer should be good enough.
The tubes need 1.26 A of filament current (EL84=0.76A - EF86=0.2A - ECC83=0.3A) and your transformer provides 1.5 A.
The HT secondaries provides 0.1 A. That's enough for those tubes.
For information on tubes you can go to Frank's electron Tube Data sheets.
If this is your first project and you have never worked in an open chassis, be careful of the LETHAL voltages. The filter caps can store the voltages even if the amp is off.
Good luck

Matt

[Alex R]

One little point - I'd advise splashing out a bit extra on a decent NOS EF86. Not a recommendation I often make, but I've never yet come across a new-manufacture one that wasn't noisy and microphonic, they must be tough to manufacture well with all that gain in there. I had a decent batch of Phillips Miniwatt that were good.