845s or GM-70 amp.

[Paul Barker]

I am struggling to get my head around this, but I think that you are saying this is a single ended output transformer, in which you must use two output valves with balanced current, one to pull current in one direction the other opposed.

To save my grey matter what happens to the secondaries?

[Polisois]

Dear Paul,
Thanks for your interest.
The pair of primaries being in positive series (each pair), their secondaries should also be in positive series, in order to keep the same turns ratio.
But you can also put them in parallel, in which case the turns ratio doubles and the resulting impedance increases according to the known formula:-
Zp = N² x Zs where Zs is the load impedance.
As you can deduct from the connections of the primaries, they are opposed for the DC, hence the offset takes place, but, the ac in each pair being of opposed phase, the signals develop freely.
By the way, I am trying to send a file ( GIF ) totalling less that the accepted size (except the unreadable image that you see), and I get a refused access. This file contains some calculations confirming that, irrespective of the anode current of each valve, the offset takes place.
Can you help me please ? For instance, if I could post the original excel file as an attachment to a standard e-mail and you could take care of inserting it in the thread (sorry but I am unexperienced in this field).
Thank you and best regards,
Ari Polisois

[Polisois]

Dear Paul,
A friend of mine helped me to convert the image into pdf format.
Here it is. I hope it works. Thank you very much for your help.

[audiodesignguide]

see this

http://www.audiodesignguide.com/Clau...st_result.html

or this

http://www.diyaudio.com/forums/attac...amp=1235224604

[audiodesignguide]

try this
http://www.audiodesignguide.com/Claudio845/GM70amp.html