DC preamp heater supply, are these tubes polarity sensitive?

[Ron]

Why DC, of course! If AC, then alternating the hookup so you get some cancellation.

[titser_marco]

Ron

Not only are the El34s wired up alternating 2 and 7...

So wait, did I get this correctly: each tube would have to alternate between 2 and 7? My wiring on 4 6L6GCs essentially had heaters terminate at the same tube socket lug,i.e. 2 into 2, 7 into 7. Much like this:

2-2-2-2
7-7-7-7

I got that idea from Gerald Weber's videos where he says that this should be how it should be wired for minimal noise. But what I got from this thread was that it should be like this:

2-7-2-7
7-2-7-2

Could anyone please clarify? And am I right in thinking that the principle shouldn't apply in preamp tubes because they cancel out anyway? Thanks!

[Andy Le Blanc]

for DC and series string, the quietest place for sensitive gain stages is on the ground end of the heater string.

I have encountered PT with flaky insulation and noisy fil. supply.

the best advice Ive found was to simply be consistent in your dress, Ive also seen a few very old hand building recommendations going back to the 30's about the order in which the rig is wired, greatly effecting the overall outcome of the quality of the project.

[Structo]

This is a great book about increasing tube life.