transformer placement

[Dimitree]

hello everyone, I'm building a Vox AC30 amp clone, and I'm stuck with transformer placement. I know I should not place OT and PT with the same orientation, but what about the choke? for it, should I use the same orientation of the PT, or the same of OT? as you can see I only can mount the transformers upright, so only 2 orientation are possible. Right now the distance between the PT and the OT is about 35cm center to center. What do you think?

 

[Osvaldo de Banfield]

The layout depicted below looks good. In any case, it is important that magnetic axes be at right angles, and so far as you can.

 

[Mark Tillotson]

Spaced well apart is always going to give good isolation, magnetic field drops off as the inverse-cube of distance, so doubling distance is a factor of 1/8, or -18dB, all else being equal.

 

[turk 182]

does the third dimension matter? and does the chassis prevent hum pickup? why are most supply chokes open frame? if so without knowing the layout of circuits below the transformers would it not be wise to move everything back as far from the front of the chassis where most of the high gain stages live?

 

[Osvaldo de Banfield]

why are most supply chokes open frame?

Because magnetic harnesses short circuit (magnetically) the gap in the core and make inductance difficult to calculate and predict. It also happens with all cores with DC superimposed, as in audio output transformers single ended. Look, for example, my regen output trafo made from tube vertical TV deflection core and harness. There is a cut near the gap site to prevent core saturation and gap short circuit (Bottom left of the pic).