Gyraf G9 Preamp PT Question

[sarakisof]

Hello folks  i am about to build the Gyraf G9 PreAmp and i need some advice about Power Trafo.
My local shop has two toroid transformers that i think are ideal for G9 PT's.
But in the site they use Watts instead of VA rating and just want to be sure.
I am planning to use one 2x15V and one (backwards) 2x12V instead of two 2x15V's.

I am in Europe.
I copy paste their description from local site here:

230V --> 2x15V 50W  and
230V --> 2x12V 30W 2,5A (230V-->2x12V 15W 1A).

Is the second one ok for backwards wiring 2nd 30VA G9 trafo?

Schematic: http://www.gyraf.dk/gy_pd/g9/KevAndByronG9_a_files/G9_7_sch.gif

[antonis]

Sofoklis, by using 12 -> 220 instead of 15 -> 220, you'll result into about 275VAC across BR1..

According to TL783 datasheet,
https://www.ti.com/lit/ds/symlink/tl783.pdf?ts=1605726067187&ref_url=https%253A%252F%252Fwww.google.com%252F
max IN-OUT differential voltage is restricted to 125V..
3 X 39V zeners take care for ensure 117V differential voltage so you'll only have to count for the extra current through R33 due to extra voltage..

P.S.
Make your calculations instead of waiting for a neat OK..

[antonis]

I am planning to use one 2x15V and one (backwards) 2x12V instead of two 2x15V's.

Is power inequality misunderstanding settled down, now..??

[sarakisof]

Yes, but i am having another trouble now here Antonis. The 2x15 local toroids from "Amrad" arrived  and i just realized that the secondaries use 3 wires, 15-0-15. They are center tapped, not isolated, so no-no for the triple phantom power. It's not my fault, as there was no pics in the site and description was just "2x15V toroid".
I guess i cannot use none of them right?

http://www.gyraf.dk/gy_pd/g9/g9_sch.gif

[iainpunk]

you can still use the transformers like this:



you should of course still use the regulators described in the original schematic

cheers, Iain

[sarakisof]

you can still use the transformers like this:



you should of course still use the regulators described in the original schematic

cheers, Iain

Sorry, no pic or file can be seen. Please upload again. I don't think i can do smthng for this though.

[iainpunk]

well, in another browser than the my main one, i can's see any postimg.cc images. ill try another service.

[antonis]

Does postimg.cc sucks recently..??

[iainpunk]

Does postimg.cc sucks recently..??

yes, unlike my gf.

cheers

[antonis]

Does postimg.cc sucks recently..??

yes, unlike my gf.

You have my empathy but c'est la vie..