TRANSFORMERS FOR VALVE RECTIFIED AC50s


Majestic Transformers in Poole (Dorset) have original specification sheets for several AC50 transformers. The sheets were evidently drawn up by someone at Vox - presumably at Dartford Road - either on the basis of sheets provided by the transformer suppliers, or by breaking down specimen units.


Two of the transformers are described as being complex in structure, having silver shrouds, and large stacks. One is wound normally; the other reverse phase wound.


Effectively these two correspond to the transformers used in early small-box AC50s.




Above, the winding styles of two output transformers: above, simple; underneath, complex. Image from the wonderful Lenard Audio website. The complex form corresponds to the early AC50 large-stack transformers - pairs of wires for each side of the primary - P1 and P3 on one side, and P2 and P4 on the other.




The second of the two early transformers on file at Majestic is reverse phase wound - effectively the wire of two of the windings (P2 and P4) was wound in the opposite direction from the wire of the other two windings.


The result of reverse phase winding is said to produce an output transformer capable of reproducing a greater amount of bass. It is possible (no more than that) that these transformers were reserved for AC50 bass amps - ie. ones destined to be matched with bass cabs.


Majestic also has the schema for the later black-shrouded transformer (the type registered at the foot of this page).




TYPES OF TRANSFORMER IN SURVIVING AMPS


Transformer types are numbered simply for convenience. When an existing type reappears in a later species of amp, the number is repeated.



Small box amps


TWO INPUT AC50s



DIAMOND INPUT AMPS










Large box amps (still valve rectified)







For reference, a Triumph-made AC100 - mid 1965 - red, yellow and orange primaries. At around this date, Triumph were using a similar-looking transformer for the AC100s they were producing on a fairly fitful basis.






TRANSFORMERS FOR SOLID STATE RECTIFIED AC50s - 1965 on.

The AC50 mark 3 (mark III)