Voltage Doubler / Heater Regulator

[paulster]

Reference your DC side to ground and leave the AC side alone. That is the quietest solution since it's the preamp tubes where noise gets in. The gain at the power tubes is too low to be affected, and in a push-pull amp you've got common-mode rejection anyway.

I'd still go 6.3Vdc for the preamps though, as you're trying to pull 1/2 amp off a voltage doubler which means massive amounts of capacitance required to get a smooth rail to then regulate. As soon as you model voltage doublers in SPICE their limitations become very apparent. And there's no point trying to limit the magnetic field radiation when you're using DC anyway.

[Smitty]

This is an ancient tube problem. Most of the noise and buzz in preamp tubes can be significantly reduced by employing an adjustable virtual center tap. Fender's hum control actually works well when used properly. Problem is many turn it all the way one way and ground one side of the heater supply.

I like a 50 ohm trim pot with 47 ohm resistors on each leg and the wiper to ground. This provides easier adjustment and does not allow grounding of the windings.

Plug this part number into mouser: 774-201XR101B

An ungrounded bridge rectifier with a big cap works well in combination with a humdinger. Easy to build and a low parts count.

[paulster]

This is an ancient tube problem. Most of the noise and buzz in preamp tubes can be significantly reduced by employing an adjustable virtual center tap. Fender's hum control actually works well when used properly. Problem is many turn it all the way one way and ground one side of the heater supply.

But, there you go. "Significantly reduced".

A properly designed, regulated DC supply doesn't significantly reduce the level of AC hum, it absolutely eliminates it.

An ungrounded bridge rectifier with a big cap works well in combination with a humdinger.

Have you ever tried comparing grounding the AC side as you suggest versus leaving the AC side floating and grounding the DC side at V1? Way quieter in my experience.

But both of these are still way, way short of what you can achieve with regulated DC. A bridge rec and a cap means you'll end up with a sawtooth wave riding on your DC at 120Hz which can actually make the situation worse than running AC in the first place. Plus 120Hz is more annoying as it's getting into the more sensitive range of hearing, and a sawtooth wave sounds nasty compares to a sine wave.

Seriously, if you're going to do DC (and this is why most manufacturers don't bother) you need to do it properly or you're setting yourself up for a worse result than just sticking with AC.