Twists per Inch

[snitch56]

Is there an optimal “twists per inch” when hooking up output and power transformers or any rules of thumb?

[TomMcNally]

My opinion ...

Twist the AC leads as tightly as possible, but not so
tight that you use too much length twisting.

Twisted leads are most important on filament leads
that go to the tube sockets, and otherwise mingle
with the signal leads. Keep them up against the
chassis and away from input leads as much as
possible.

On the output transformers, there is no advantage
to twisting, since there is no AC to cancel, so just
do it for looks if you want ... it can't hurt anything.

[snitch56]

Thanks for the reply Tom.
Do you think it is possible to twist the wires too tight by hand causing cracking to occur in the Teflon insulation of a new power transformer on the smaller gauge wire? The Teflon insulation just seems thin and brittle to me.

[TomMcNally]

Too tight is not good - don't confuse that varnish gunk
on the wires with insulation, it's just overspray on some
transformers from the coating. Hammond is famous
for that - the Dynaco stuff is much better.

A good layout helps ... keep the AC leads as far
from everything as possible. Lead dress and
parts placement is important, but the AC fields
from the wires don't travel all THAT far.

[erichayes]

On UL output transformers, I've found that not twisting the screen and plate leads (letting them go their own merry way) increases the potential for positive feedback and instability--which translates into distortion. My only theory for this is, that because the signal voltage for the two is in phase and of near equal amplitude, not physically treating them as one wire allows them to radiate into different points of the input and drive circuitry. In general practice, all OT primary leads should be kept as short as practically possible, and should hug the deck. I've never tried running the plate and screen wires not twisted, but held together with zip ties. One more thing to put on the things to do list . . .

[nyazzip]

man, i twisted naught on my st-35 that i just finished. i just figured you guys were being perfectionists. lo and behold there is a practical reason for the pretty wiring, huh...AC noise cancelling...
guess i'll have to open her up and do the twist...probably when i reroute the power switch to the front- i don't like doing the reach-around grope over hot tubes and transformers...i'm still a little scared of my amp, to be honest... anything shiny metal, warm, thats plugged in, that i assembled, scares me. i want to see what i'm touching. plus, i kind of melted my plastic toggle switch when soldering, so it toggles a bit squirrely. it buzzes angrily if i am not decisive enough with my "off" thrust...
anywho, what do you use to retain the wiring against the chassis walls? do i need to epoxy little harnesses here and there?

[TomMcNally]

Yep - you have to solder quickly on those cheezy plastic
switches. Putting in the front is an invitation to hum
unless you do it right.

I don't tie the wires to the chassis, just keep the inputs
away from the outputs and you'll be fine.

Don't use those stick-on things, they will fall off in months
after heat hits 'em.