B15N build question about heater elevation

[Bieworm]

Hey guys

I've been wondering about implementing a 50VDC heater elevation circuit on a planned B15N build.
It "looks like" tapping from the 50V bias tap of the power transformer is easier than creating a voltage divider on the B+. I've read a post on this forum where that is discussed and found to be a good idea. But when I googled " heater elevation on 50V bias tap" the AI answer is completely the opposite:
Why Not Use the 50V Bias Tap?
Low Current:
Bias supplies are designed for very low current (a few mA) and are high-impedance, which makes them unsuitable for driving the heater supply and achieving a stable elevation voltage.
Impedance Issues:
Connecting the heater supply to a 50V tap could result in an unstable or noisy elevation voltage, and could also affect the bias point of the power tube.
Not the Intended Function:
The purpose of heater elevation is to improve signal-to-noise ratio by moving the heater reference point above the cathode, which is not the function of a bias tap.
So now I'm confused whether to do it on the 50V tap or not.

here's the post on EL34world: https://el34world.com/Forum/index.php?topic=30961.0#google_vignette

[Willabe]

Not hard to build a dc heater stand off, 2 R's and a cap.

[stratomaster]

AI isn't an amp tech.

The bias tap isn't special. It's just a 50v ac supply.

The bias supply itself is a half wave rectifier that conducts only when the negative swing of the AC wave exceeds the diode forward voltage.

Using the bias tap for elevation mirrors this arrangement except for the positive swing.

This means neither supply is conducting simultaneously.  They do not interact, and neither one "knows" the other is there sharing the tap. Furthermore, the diodes themselves provide circuit isolation so the two supplies do not interact even when neither is conducting (there's a brief period where neither diode is conducting and the caps are discharging).

In both the heater artificial CT and the bias supply the current is very low.  The voltages, especially in the case of DC heater elevation, are just a reference. I also spec'd a relatively high fixed resistor to ground to further reduce the current through the elevation reference voltage supply. 

You can also go further and use fusible resistors to act as a safety measure if you're concerned about a heater short taking out the bias supply. But again, the two circuits are diode isolated.

I don't see a downside to using essentially an unused voltage source (positive swing of the bias tap) to create a DC reference in the configuration I've sketched up.

Both amps I've done this on are working perfectly and with less background heater hum than before.

[Bieworm]

Thanks!👍