OPT ultralinear taps, which end?

[Disco Volante]

Pardon me if this is banal, I'm just having so much fun finally getting into the fine art of winding transformers!

Studying the literature on the subject, I am somewhat confused:
Which end do you count the 48 or 20 or 25% from?

For example: CJ seems to place his g2-taps 20% from the anode end (for guitar amps). Morgan Jones "Valve Amplifers" seem to count from B+ end of coil.
Old schemos rarely agree either...
Thanks, Viggo

 

[volker]

From the anode ends, not the middle. I've also seen them defined as 80%, then it would be the other way around.

 

[Disco Volante]

Vielen dank;-)
Volker, do you have a calculator/spreadsheet/program for calculating transformers you can recommend? I am trying to read up on the math of it, and you were so quick to help me out earlier?
Cheers, Viggo

 

[CJ]

Good question on the tap percentage, i have seen it both ways, and today i found a third way, percentage of transformer impedance, talk about ambiguous,

dertimation of tap % seems to be done experimentally as the math is cumbersome.

here is a good article from Langford-Smith , 1955, too big to upload,

https://www.pearl-hifi.com/06_Lit_A...ol_01/Sec_02/081_Ultra-linear_Amps_w_Refs.pdf

 

[Disco Volante]

Alas, "Table 1" in this interesting article counts from the B+ end... Confusion is total.
Well, since I'm rolling my own, I can make taps from either end and measure (power, distortion, linearity) both ways once I get the amp together...
43% turns seems to be the recommended ratio for hi-fi. I guess guitar amps would often opt to tap closer to pentode operation (20-25%) for increased power?

Cheers

 

[CJ]

Having a switch with a bunch of screen tap points would be cool, would have to be a good switch.

I think McIntosh use to cross the screen taps to the tubes , but their windings were unusual with part of the transformer sitting under the cathode.

Sunn had a few UL guitar and bass amps I do believe.

 

[Disco Volante]

Yeah, I was thinking along those lines, I just might have the right Elma-switch lurking somewhere.
The Quad II (of which I own a pair) also has a part of the transformer in the cathode end...