DC Heater Supply for Valve Power Amplifiers

Looking at a design for a DC valve heater (tube filament) power supply.
An off the shelf switching supply is modified and additional circuitry employed to clean up the supply and add a true soft start function.
There are other circuit arrangements that do similar things, a current limiter is the obvious one. Current limiter circuits come with extra losses however, probably near 3 watts in this application and the soft start does not start from zero volts.
This is a building block for a Valve Power Amplifier.
• KT88 Valve Power Ampli...
• KT88 Valve Power Ampli...
• DC Heater Supply for V...

[@lloydieization]

I'm trying to a build a Tube amp too, not an electronics guru, but I'm just using an older Linear technology LT1084 LDO regulator in the lovely TO-247 package (large heatsink contact area and easy to safely insulate) plus a Schottky diode rectifier, and I am able to use the valve transformers typical 6.3 volt AC heater taps for my regulated DC heater voltage , had to use a 16 volt 33000uf filter/reservoir cap to get the ripple down to less than 10mV (think I was down into micro volts), pretty much no audible speaker hiss (idle) or at least as good as my 2023 Marantz in my initial amp testing... similar to what @MichaelBeeny noted, my thoughts were, if the LDO failed 7-ish volts max would reach the heater... thinking of an 6.8 volt Zener circuit to trip a relay if the 6.3 volts was exceeded. like your videos and ideas, even though I'm an analogue purist numpty. This purist wants to put a Pi Zero etc for music steaming and or a microcontroller Cricut (Arduino etc) for safety monitoring (voltages, music detect auto power off, soft start etc...) in said analogue amp 🤦‍♂. That said, especially NOS Tubes, are "hella" expensive so the idea if I can pull it off isn't too mad. We Amp/Audio folk are all a bit crazy ;-)

[@Mr_Wh1]

Thank you for these videos. I do enjoy them for some late night watching. What is up with the flashing blue squares like the one at 8:54?

[@myalbatech]

Thank you! Forgetting to turn auto focus off is the cause of the flashing squares

[@breakfastbuddy5]

linkfor power supply ?

[@MichaelBeeny]

In all the many years I've worked with valves, I've never known a valve heater fail on switch on. With this interesting power supply, you have even less chance of heater damage, but what you do have is a high probability of the SMPS failing. These low cost SMPS are really unreliable. Apart from the visual aspect of a valve amplifier, these days I fail to see the attraction of 1940s technology. A modern solid-state amplifier will simply sound many times better than ANY valve amplifier. However, if you are not bothered about the sound, they are great fun to build and watch them heating the room and burning lots of very expensive power. Good video, however.

[@myalbatech]

More on reliability in a later video..