DC-DC converter for vacuum tube heaters

[b1o2r3i4s5]

Hi, I am currently building a Vacuum tube headphone amp with 160V DC rails, and planning to power the tube heaters using a switching DC-DC converter from the 160V rail, since the heaters only need 3-4W and transformers are hard for me to get. I was planning to use a non-isolated Buck Converter but they are usually used at low voltages, so what i wanted to know is:
1. is it okay to use a buck converter to step down from 160V to 12.6
2. will it cause any problems if i connect a DC-DC converter to my 160V supply rails and could i power the tube heaters with it
My power transformer is rated 110VAC 50VA output. The power supply bypass capacitor is 2200uF.

[DigitalJunkie]

A small 12V SMPS (wallwart/charger) for a cellphone,or something should work okay from 160Vdc. Most of them just rectify the incoming ~120Vac to 160Vdc anyways. Just find one with enough current capacity to power the heaters.

[jackinnj]

If it's a wall wart charger use a low dropout regulator afterward to clean up some of the switching noise.

You can use the Supertex LR8N3 to drive the base of a high voltage NPN transistor -- this device was designed to provide auxiliary power for SMPS circuits like off-line switching supplies. It's available in the US from Mouser, don't know about HK.

[b1o2r3i4s5]

Originally Posted by DigitalJunkie

A small 12V SMPS (wallwart/charger) for a cellphone,or something should work okay from 160Vdc. Most of them just rectify the incoming ~120Vac to 160Vdc anyways. Just find one with enough current capacity to power the heaters.

Thanks A lot!!! I Used a universal (110V/220V) 12V SMPS charger and it works perfectly without inducing audible noise to the amp.