Using UL taps instead of the anode taps to alter inpedence

[kanks]

Ive got a quick question. If i have a Ultra linear transformer with say a 12k primary and 50% UL taps could the UL taps be used to half the primary independence.

 

[disco]

No doubt. If you want to check measure the turns ratio (from primary UL tap to secundary).

 

[kanks]

Its more theoretical at the moment as Ive got some transformers here that I would like to use with EL34 tubes but the primary impedance is a little on the high side going by the RCA manual.

 

[Malcolm Irving]

The 50% for the UL taps refers to the turns ratio, but the impedance is proportional to turns ratio squared, so 12k x 0.5 x 0.5 gives 3k.

 

[jazbo8]

You forgot the square term, half the primary turns results in a quarter of the primary impedance, also by not using the full winding of the OPT, the frequency response is likely impacted as well.

 

[kanks]

The 50% for the UL taps refers to the turns ratio, but the impedance is proportional to turns ratio squared, so 12k x 0.5 x 0.5 gives 3k.

Excellent point. I'm looking at doing a push-pull el34 and thinking a of using the UL taps on a transformer to get into the ball park for 4 el34 tubes. I'm just confusing myself I think by thinking like this.

 

[disco]

Giving it more thought will there be enough self inductance left, using only part of the winding?

 

[DF96]

At half the winding you will get a quarter the impedance match and a quarter the inductance, so the frequency balance will be the same. You will get half the winding resistance, so a small loss of efficiency.

An extra issue is heating. You might want to run with twice the DC or signal current, but this will give you twice the heating so you may need to derate the transformer.

 

[kanks]

Well im gonna give it a go and ill let you know how I get on.