Proper wiring for LL1521 transformer 1:2.28

[Potato Cakes]

Hello,

I am using some LL1521's for a project that I'm wanting to wire them 1:2.28 as they are described to be on the Lundahl website. It says it's similar to the 1540, but then the description specifically says 1521B (mine is just 1521) and the pinout that follows does not have a pin 7 (mine does) nor does it show a corresponding layout. Being similar to the 1540 (http://www.lundahl.se/wp-content/uploads/datasheets/1540.pdf) and the same pin configuration, I wired the primaries parallel and the secondaries in series to achieve the desired ratio, but when I do my initial tests, the voltage goes from 0.766VAC to 0.91VAC, about a +1.3dBu increase which I don't think is correct. Could someone who has used these transformers provide a little bit of insight on this particular part and how to properly wire them for 1:2.28?

Thanks!

Paul

 

[Potato Cakes]

I figured it out.

It's not entirely clear as to which configuration gives you what as the info on the Lundahl site shows what I think are primaries in series and the secondaries are fixed. After some educated guesses I was able to get about +7.4dBu of gain off of the secondaries (0.766 to 1.81VAC) which is more what I am expecting. In case anyone has these transformers, here's how I wired mine for 1:2.28:

Primaries:

Pin 1+4 = In +
Pin 2+3 = In -

Secondaries:

Pin 5 = Out +
Pin 6 = Ground/shield
Pin 7 = NC
Pin 8 - Out -

Pin configuration is based on the LL1540. I hope this helps someone else.

Thanks!

Paul