Transformation

[Toxophilite]

Hello all
I have an OT question springely largely from a certain ignorance of their construction


Does a multitap OT need to be correspondingly bigger to have the same power of a single tap OT meant for the same purpose
For eg:
If one has 2 OTs of the same size and turns ratio
Both pushpull and intended for similar tubes
However one is single tap 8 ohm and the other multitap 4, 8, and 16ohms
Would they likely be rated the same as far as power handling


One is a Hammond organ OT as found in the  A0-43 amps originally using 2 EL84s in pushpull


The other is a multitap electorhome OT (LK-561-1) originally using 2 6V6s in pushpull


Both are approx 30-1 turns ratio


They seem to be identical in measurements though one has end caps and the other doesn't

[AZJimC]

IMO they would likely be near same wattage given same iron, and that they came from similar output tubes, in capacity. The actual output wattage is related to wire size, and staying within an acceptable amount of wattage loss in the windings, in heat, due to wire resistance. Wattage relates to heat 1:1, so the heat dissipated has to be carried away at an acceptable rate so as to maintain temperatures below breakdown limits.

It is my understanding that extra taps should take up only the space to get the lead out of the winding, so only very slightly more space.

As long as the windings will hold up, a given wattage output through a given mass of iron can be the limiting factor of frequency response. For example, a transformer that is rated at 20hz-20khz at 20w might handle 30 watts at 30hz-18khz. Heat would be the enemy.

[PRR]

Any multi-ratio winding is a compromise.

To get 4 and 16 without doing a series/parallel switch, for ideal proportions, you want about 1.3 times the window area but the same core area. To a first approximation you use the next-up lam-size and don't stack it so high. Then re-do your calculations to allow for the longer MLT.

In practice an OT heavily favors the primary, the secondary has to fit the space left. Significantly non-optimum DCR in the secondary has little effect on the sound.

> 2 OTs of the same size and turns ratio

There's probably a LOT more differences than size and taps. The older Hammonds were sold to churches, very carefully designed and wound for best musical effect; the later el84 era Hammonds maybe not so much. The ElectroHome is from a nice-case phonograph, no? It is better-than-cheap but not fabulous.

I think you pick the one that looks/fits best, or leave them loose and try both.