I'm considering using an old laptop power brick for a simple 12AX7/6BQ5 SE amp. 19V and 7 amps to 250VDC for B+ and 6.3VDC for the heaters. I am looking at a switching AD/DC converter for the B+ (I am told the switching frequency is well above human hearing), and a DC-DC LM2596 buck converter to get the 6.3VDC for the heaters.
The buck converter is rated at 3A, and I believe that should be fine for the 3 tubes involved.
However are there any considerations I am missing?
The buck converter is rated at 3A, and I believe that should be fine for the 3 tubes involved.
However are there any considerations I am missing?
I will work in principle, but the converter might refuse to start into the cold resistance of the heater, in which case you may need to implement a soft-start feature. Try it, maybe it will be happy.
I've used the very cheap ebay XL4015 based pcb assemblies for heater powering, although only for 0.45A heater from a 12Vdc supply, but the specs seem appropriate. The control IC may well hiccup a few times during power up if the cold heater current exceeds limits, but that likely returns to normal constant voltage operation as the heaters warm up, so is really of no issue.
I used a buck converter for heaters to make a simple matching jig. Just ran at current limit for a bit, then settled at 6,3V.
I have used on from Ali that works well. It’s 300w and 20a max and takes up to 40vdc input down to as low as 3v. It does several amps at 6.3v with no problem. I just got 3 delivered for less than $15. It’s so inexpensive you can try it and if you don’t like it use it for something else. It also has the ability to limit current.
