Hi,
I'm trying to use a 60 volt battery to supply a simple 12ax7 tube preamp circuit. What would be the best way to drop the voltage to 12.6 or 6.3 VDC? I need this to be the cleanest way to eliminate hum in the circuit.

 

LMR38010 should do the job. You might need extra filtering to remove the high frequency ripple, You might have to test how much hf ripple makes its way to the cathode, as no one was using 400kHz switched-mode supplies in the days of the 12AX7!

Even smarter would be to use a valve designed for series-connected heaters and run it using an LED constant current driver. That way, you would avoid any problems with the inrush current when the heater is cold.

 

It would be a better plan to add in a 6-Volt Battery for the Filament.
Old-School portable Radios did it this way.
.
.
.

 

A separate low-voltage battery is typically used for the filaments, since they have a high current draw and it would be more efficient than trying to generate it from the 60V battery.
You will just likely need to change the filament battery more often than the 60V plate battery.

What 60V battery do you plan to use?

 

You might need extra filtering to remove the high frequency ripple,

At 2.2 megahertz (!), I doubt that it will audible.

And - ebay:

https://www.ebay.com/itm/2042665607...HFZ2+1sckgXGrVtETHPZldUQ==|tkp:Bk9SR57P06jIYg

https://www.ebay.com/itm/4042347814...COQs0OAKMiqopPMSjd84DWVQWn|tkp:Bk9SR-zpwKjIYg

https://www.ebay.com/itm/1237591141...RKYdKbktQ0L/Uc5TwListQLUj0|tkp:Bk9SR57P06jIYg

ak

 

LMR38010 should do the job. You might need extra filtering to remove the high frequency ripple, You might have to test how much hf ripple makes its way to the cathode, as no one was using 400kHz switched-mode supplies in the days of the 12AX7!

Even smarter would be to use a valve designed for series-connected heaters and run it using an LED constant current driver. That way, you would avoid any problems with the inrush current when the heater is cold.

Yeah, that was my question. Is there only one tube in the circuit, or do you have a few you could put in series? A voltage regulator would be dreadfully inefficient for such a large drop

 

A separate low-voltage battery is typically used for the filaments,

It would be a better plan to add in a 6-Volt Battery for the Filament.
Old-School portable Radios did it this way.

I agree.

Considering the scarcity of 60V batteries, it might be better to use A 12V lead-acid battery for the filaments, and use a switched-mode to produce the anode voltage. A 12AX7 only takes 1.6mA and anode voltage of 60V, and about 1mA biased to 2/3Vb, so the power required will only be small, unless the circuit has a lot of 12AX7s.