2503 unused secondary?

[Helsing]

Ive got a 2503 wired 1:2 Im not using the spare secondary. Is there anything wrong with leaving it unhooked? Perhaps there is a better way to configure the windings given that I dont need the spare secondary.

Helsing

 

[CJ]

No problem. That's a quad litz winding so all four windings go around the core in the same manner.
Use it for a vu meter if you want.

 

[rafafredd]

or wire it as 1:3 for more output / free gain / headroom.

 

[Helsing]

Thanks guys. I think what Im asking is this. If I wire it 1:2 is there something wrong with leaving the spare secondary completely unhooked?

Helsing

 

[CJ]

No. Just don't short it out. A little black tape.

 

[Helsing]

thanks cj

helsing

 

[edanderson]

not sure if it was application specific or not, but i ended up paralleling the extra winding with the one i used as my primary. not only did it work fine, but i measured a bit more bass extension. this was using a 2520 in a 312 circuit. if i can get the rest of the preamp finished, i'll try to make some screenshots with and without the 4th winding connected in parallel to the primary.

ed

 

[Bauman]

not sure if it was application specific or not, but i ended up paralleling the extra winding with the one i used as my primary. not only did it work fine, but i measured a bit more bass extension.

:shock:
cool!

 

[rafafredd]

so, now it´s 1:1 ?

 

[edanderson]

no, primary parallelled with another primary to a secondary in series with another secondary, so 1:2. i don't think adding another winding in parallel with the one i'm using as a primary changes the ratio.

ed

 

[rafafredd]

Oh... I´m silly!

But the strange thing is that another winding in parallel would lower the inductance, so you should, theoretically, have LESS bass with another winding in parallel. But it seems that you got the opposite.

Or am I thinking wrong again?

It would be nice if some transformer master could explain it...

 

[CJ]

Raf, as the turns go up, the inductance goes up.
So when you connect the secondary windings in series, you have twice the turns and four times the inductance. (roughly)

When you paralell the windings, the turns stay the same as one secondary section.
This is because all you really have is a two stranded piece of wire, as they are joined at both ends. The core see's the same amount of turns. It does not care that you have changed the wire from one strand to two strands.

Ed decreased his dc resistance by half when he paralleled the windings.
This might have something to do with the tweaked bass response, but I am not smart enough to know why.

cj

And Happy Christmas, Merry New Year!
:guinness:

 

[rafafredd]

Thanks, CJ. Got it. So, in fact there´s not a big diference when you parallel the windings in the same core... Just DC resistance decreases 1/2 of the value. Nice!

 

[PRR]

> am I thinking wrong again?

Of course!

> ...another winding in parallel would lower the inductance

Not when they are on the same core, with the same magnetic flux. Inductance is unchanged.

> Ed decreased his dc resistance by half when he paralleled the windings.

Bingo. It isn't a problem in "L", it is an "L-R" problem. With very low impedance drive, the ultimate bass fall-off frequency is a function of winding R. So you want to fill the available space with copper. If you use only half the available space (when using one winding of a dual-winding) you get double the R and double the -3dB frequency. (But in most "power" transformers, even only +20dBm, the bass response is usually FAR below 20Hz.)