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This week a power transformer and choke by Alexander Naydenov were delivered. The idea was to build a second power supply as both the AD1 preamp and 101D preamp share a power supply, thus can not be used simultaneously. Might be an interesting comparison as well to the old stock Stoet transformers that are already in use. Voltages and choke rating are kept just about the same as are the rectifiers and capacitors. Alexander delivered a choke with dual coils for both series or parallel connections but also suitable as common mode choke.


Both coils can be used in different ways..

The latter is what I chose so the supply is a bit different in configuration. Where the current supply has traditional C-L-C the new one has C-L(common mode)-C. Also the rectifiers are the same, be it a different brand: Telefunken versus TeKaDe, however most certainly from the same factory..

Alexanders' power transformer is winded way different than Stoet. Not only a different core  (EI or M versus C) but also in technique. Where Stoet uses a single bobbin and single sections per voltage, Alexander uses two bobbins and winds voltages symmetrically across the two bobbins, interleaving and equalising so that each half secondary of a centertapped full wave rectification gets low leakage flux preventing ringing in the audio band. This technique also puts less stress on windings, thus considerably reducing noise. Stray fields are reduced as well. When testing the new supply this proofed to be true as the power transformer was totally silent: no buzz or hum audible.

Some pictures below and soon a report on sonics!