Audiostatic esh50 renovation project

[MJ Dijkstra]

Thanks for the useful tip about the Triad.
Of course a single transformer also provides galvanic insulation, but two of them were used to feed the cascade with 230 volt again. Those small transformers are also commonly available and relatively cheap.

Unless it is an auto-transformer, don't most power transformers provide galvanic insulation without needing to resort to the dual transformer setup? Come to think of it, if one transformer isn't providing galvanic insulation on its own, a dual setup wouldn't either right?

The TRIAD dual bobbin Flat Pack transformers are nice because they have plastic dividers built into the bobbins to ensure primaries and secondaries are kept separate from each other rather than just winding secondary over the primary. Specifications state primary/secondary isolation is tested at 2kV.

 

[bolserst]

Oh, so the dual transformer setup was used because 230V primary / 230V secondary transformers were not readily available. Is that correct? If so, it is a good solution using available parts.

 

[MJ Dijkstra]

Oh, so the dual transformer setup was used because 230V primary / 230V secondary transformers were not readily available. Is that correct? If so, it is a good solution using available parts.

Yes I assume the designer of tbe circuitry had this in mind.
I.build the same cascade, slightly modded with an input resistor to limit switch-on surge current, added a neon oscillator at the output and a LED fed from the low voltage side of the transformer. Works great but the pcb is quite large.

 

[johnsurnamerobinson]

I allways had my eht transformers wound on double bobins for isolation far far safer.
BTW they were not for electrostatic speakers.