Any reason to not use an atx power supply for dc to filament/heaters ?

[J M Fahey]

620V across a 450V rated electrolytic?

85W dissipating 1 k loads across a 290V badly dropping overloaded supply? (which started as 340V)
Not surprised by the smoke.

Poor/bad/nonexistent/incomprehensible descriptions about dangerous high voltage circuits?

Why do I start to see this thread as a dangerous trainwreck?

[Chuck H]

..

further testing will include 450v caps in series.

[tnmgcarbide]

from the rca receiving tubes manual p348 .for 6v6gt .july. '63

Plate voltage-315 total harmonic distortion-12%
plate voltage-250 total harmonic distortion-8%

[Helmholtz]

from the rca receiving tubes manual p348 .for 6v6gt .july. '63

Plate voltage-315 total harmonic distortion-12%
plate voltage-250 total harmonic distortion-8%

Ok, I see.

The THD values in these design examples are not directly comparable as they refer to different power output and different plate loads.
Typically the THD of a well designed stage increases when you lower the supply voltage.
And of course, THD drops below max. output.

Are you building a guitar amp or an hifi amp?

[tnmgcarbide]

that's interesting . perhaps i'll rearrange things here to suit the voltages. i'll have to sort through my pile of OTs , but a higher voltage , 6l6
or el-34 might give me what i'm looking for in a hifi application. i have a case of these 24v transformers , so if i needed more current i could
make two power supplies -two in series and a 24v for the heaters .. i'll just need two identical OTs .. if i have to , i'll bite the bullet and buy a couple triad or hammond ot's .
yeah... they cut out @around 15khz . same as the FM radio broadcast limit . the speakers i intend to use don't produce extreme frequency limits anyway..
i have a bunch of RFT dimple-tops that could work out. we'll see.