Balanced Power Isolation Transformer

Hello, everybody!
I want to build a line isolation transformer, as when bombing infrastructure in my country appear, there are days when there is good electric line and some days i cant listen to anything because of the hum on transformers on my devices and signal, and unwanted oscillations too. I have all tube system, with proper grounding available.
For these purposes I have a winder-guy but need to make a proper task for him to do. So what are the requirements for such a transformer? Plan is to build several, big for AMPs, small for signal, another small for digital. What is inductance, resistance, bifilliarity or other tricks I need to indicate in the task?
Thank you so far.
 

TNT

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Joined 2003
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One big single is better as it will make all units sit on the same potential and thus, minimise inter unit currents. It can be felt by touching a metal chassis as a "buzz" on the fingers.

Do a 5 KVA, 230 in, 115+115 out with an electrostatic shield between the prim and sec. Potted.

Connect all units to the trafo, but without the intrerconnects - in the stage, take a multimeter, put it in AC mode, hold one lead in your hand and the other to the chassis of a unit - here you should turn the mains socket so that the least reading of AC is achieved. Repeat for all units and when finished, connect all signals and enjoy the music. Buzzing fingers should be gone.

You will need a softstart... build one using a AC relay and a power resistor.... put the resistor in series with the hot lead of the incoming 230 and the relay in parallel with the resistor - once the field has been built up in the trafo, the current will go down - this takes a few cycles of 230 and as it is so short - the resistor will survive.

#23 + #34


This instruction is only something I heard about - never tried myself ;-) so no promises or warranties whatsoever....

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One big single is better as it will make all units sit on the same potential and thus, minimise inter unit currents. It can be felt by touching a metal chassis as a "buzz" on the fingers.
I am not sure, as I have streamer dac which is in distributor with other tubed gear make system inaudible because of buzz, only helps when switch it through AVR (which isolate from line too), so I belive 2 at least needed. Thanks for comments, and link to soft start solution!