10k and 6k primary windings on OPT. Use for UL?

rongon · 2nd November 2011, 03:21 PM

One of the nicer pieces I've collected is a pair of UTC LS-63 OPTs, which have 10k and 6k primary windings. (3.75, 7.5, 15 and 500 ohm secondary windings.)

Since Ultralinear config often calls for 40% taps on the primary, I was wondering... Do those 6k taps on my LS-63's represent 60% taps or 40% taps?

I have a feeling that a 40% tap would be 40% of winding common to plate and screen, and so the remaining 60% to the plate alone, but would like confirmation on this.

Thanks...

-=|=-

DF96 · 2nd November 2011, 04:21 PM

A 6k tap on a 10k winding is at 77.5%, so almost triode mode. I guess you could turn it round and have 22.5% tap instead. As a general rule, UL works best with transformers designed for UL as the requirements for tight coupling and inter-section stray capacitance are more demanding than a normal OPT.

Try it, but don't be surprised if it has HF instability.

TheGimp · 2nd November 2011, 04:28 PM

Np/Ns=SQRT (Zp/Zs)

SQRT (6000/10000) =77.4%

rongon · 2nd November 2011, 05:53 PM

OK, hmmm... I see. Thanks.

2nd November 2011, 03:21 PM	#1
rongon diyAudio Member Join Date: Jul 2009 Location: Across the river from Rip's big old tree...	10k and 6k primary windings on OPT. Use for UL? One of the nicer pieces I've collected is a pair of UTC LS-63 OPTs, which have 10k and 6k primary windings. (3.75, 7.5, 15 and 500 ohm secondary windings.) Since Ultralinear config often calls for 40% taps on the primary, I was wondering... Do those 6k taps on my LS-63's represent 60% taps or 40% taps? I have a feeling that a 40% tap would be 40% of winding common to plate and screen, and so the remaining 60% to the plate alone, but would like confirmation on this. Thanks... -=\|=-

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2nd November 2011, 04:21 PM	#2
DF96 diyAudio Member Join Date: May 2007	A 6k tap on a 10k winding is at 77.5%, so almost triode mode. I guess you could turn it round and have 22.5% tap instead. As a general rule, UL works best with transformers designed for UL as the requirements for tight coupling and inter-section stray capacitance are more demanding than a normal OPT. Try it, but don't be surprised if it has HF instability.

2nd November 2011, 04:28 PM	#3
TheGimp diyAudio Member Join Date: Aug 2009 Location: Johnson City, TN	Np/Ns=SQRT (Zp/Zs) SQRT (6000/10000) =77.4%

2nd November 2011, 05:53 PM	#4
rongon diyAudio Member Join Date: Jul 2009 Location: Across the river from Rip's big old tree...	OK, hmmm... I see. Thanks.

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