OK on this little A12 amp, I am measuring a 20:1 turn ratio on the 8ohm tap and that = 3.2K primary. On the UL/screen tap I am seeing a 10:1 turn ratio on the 8ohm tap and that would be 800ohm.
Am I right in assuming then this is a 25% UL tap? Or is that a 50% tap. I get the 3.2K part but not sure how the UL/screen tap ratio part works.
I did just measure a known 3.5K into 8 ohm 40% tap SEUL transformer and got 21:1 on the primary and 8:1 on the UL so sounds like this other A12 one is a 50% tap?
This also now has me wondering, is this a PP OT they put into a SE amp? That would explain a lot.
Am I right in assuming then this is a 25% UL tap? Or is that a 50% tap. I get the 3.2K part but not sure how the UL/screen tap ratio part works.
I did just measure a known 3.5K into 8 ohm 40% tap SEUL transformer and got 21:1 on the primary and 8:1 on the UL so sounds like this other A12 one is a 50% tap?
This also now has me wondering, is this a PP OT they put into a SE amp? That would explain a lot.
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Hello there,
UL percentage is defined by the linear amount of primary voltage swing that is fed into the screen grid. Pure 100% fed signal means the screen follows the plate, so is equal to triode mode.
A 10:1 UL tap to secondary ratio compared to a 20:1 primary to secondary ratio truly means 50%.
UL percentage is defined by the linear amount of primary voltage swing that is fed into the screen grid. Pure 100% fed signal means the screen follows the plate, so is equal to triode mode.
A 10:1 UL tap to secondary ratio compared to a 20:1 primary to secondary ratio truly means 50%.