1176 Output "custom" transformer

Is there any info about 1176 output transformer(s) ? There are 3 differents irons across all 1176 REV´s

Differences in sound ? thd ? core type and windings? etc

Any info will be appreciated !

the three types AFAIK:

5002:
a special design, with tertiary feedback and DC balance windings. the core is gapped because the supply current flows through the primary. a fairly complicated design, and optimized for the class A output circuit, similar to the 1108 preamp.

B11148:
when the output circuit changed to a class AB design based on the 1109 preamp, the output transformer changed as well. not gapped; four equal ratio windings, usually wired as a 1:2 stepup. also used as the output transformer in the la3a.

12614:
a simpler design, with a 1:1 ratio, adding no gain but providing a lower output impedance.

all three are EI steel core transformers. as for differences in sound, the change from the 5002 to the B11148 coincided with a complete redesign of the output circuit, so it isn't a fair comparison. the B11148 and 12614 are more similar, but different enough, and with enough minor changes to the 1176 circuit that i doubt that is worth debating either.

ed

Thanks Ed ! :thumb:

Do you know dimensions or lamination number for the 1176 AB output circuit trafo ? (not gapped). I will like to wind this trafo. I need to make some caculations about turns, etc.

I mean B11148 and not 12614

EI625, 0.65" stack

Thanks Ed again for the reply, now time to diy !
:grin: