Choosing OT from OT's

[petemoore]

This amp has a Large PT, and two small OT's, 9 pin sockets...
Old amp of unknown.
How do I determine the reflected impedance ?
I put 7.6Vac in one side and got .3v out the other.
That I figure as a 1:26 Ratio..
So if I'm using an 8ohm speaker, that'd be 8ohm x 26 = 208 ohms...
But this is a single ended EL84 amp I'm 'designing', and for that 5200 ohms, quite a mismatch...
so leaves the questions:
Where have I made mistakes ?
If not what output tube might this amp...er might make use of the OT here/
It was a stereo amp so I have 2 x output transformers to work with [+ transformers...er...other OT's and transformers..]
What ratio matches 8ohm load to 5k2 impedance...650:1 ?

[stokes]

You are leaving out a step.You must square the 26 and get 678.Then multiply the 678x8ohms and get 5408.This is assuming you got the turns ratio properly.I usually start with a 1/2 volt across the secondary.I didnt bother to check your math to arrive at the 1:26 ratio.Looks like you are in the ballpark for the EL84 you mentioned.

[petemoore]

Ah !
That's cool !
I know I read a page by RG on how to do this, but mahn I googled for something similar, thanks stokes, i think I can remember it this time !

[Satamax]

Ah !
That's cool !
I know I read a page by RG on how to do this, but mahn I googled for something similar, thanks stokes, i think I can remember it this time !

http://www.radioremembered.org/outimp.htm

[petemoore]

Saved, thanks guys.
Fired right up too !
Although the OT's are kind of small, they are working, I have some bigger ones, not sure what they're for..
I'll probably be going through my Xformers to see what I can find, one candidate has 6 or so wires out of each side, and looks twice as hefty.