U47 fet Transformer

Hi,
any information about wich kind of transformer has been used in U47 fet? I've read that they were somewhat BV-08 but with different windings, any winding paper like BV-08 posted on this forum?

Fra

Cinemag has done a faithful recreation of the U47 FET with their CM-13101 transformer :

http://cinemag.biz/mic_output/PDF/CM-13101.pdf

Cheers.

I'm not understanding too much, on this paper it's write that turns ratio is 9.0:1, then it's write 16.2k:200 so it's not 9.0:1 and on the table lower it's write 9.1:1...what is the ratio of this trafo?!?!

Fra

BraFra said:

I'm not understanding too much, on this paper it's write that turns ratio is 9.0:1, then it's write 16.2k:200 so it's not 9.0:1 and on the table lower it's write 9.1:1...what is the ratio of this trafo?!?!

Fra

Click to expand...

The impedance ratio is the square of the turns ratio, which is also the square of the voltage ratio, as shown in the following equation:

    Zp/Zs = (Np/Ns)2 = (Vp/Vs)2

For 9:1 turns ratio, it corresponds to an impedance ratio of 81:1.  This means that if you put an 200 ohm load across the secondary, you will get a reflected impedance of 16.2k ohms across the primary.  If you put a 600 ohm load across the secondary, you will get a reflected load of 48.600k ohms. As you can see, the transformer has no inherent impedance, it merely reflects the load impedance back to the primary. In this case I think that calculated ratio is 9:1 but because of core losses it measures 9.1:1. Not a big deal
Hope this helps