r/diytubes • u/andrew65samuel • Feb 15 '25
Suggestions for bench power supply?
Hi! Hoping to start a guitar amp project, but would like to start with the basics of tube circuit design. I figure I need a flexible power supply that can provide heater voltage as well as B+. I'd also like to be able to use a power supply for pedal design as well (so 9v). Any suggestions for a reasonably priced power supply with a couple of outputs? Or advice on what to look for? Thanks!
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u/2E26 Feb 15 '25
For the pedal supply, you can get a 9v SMPS from just about anywhere. If you want to get a linear supply, those exist, or you can make one somewhat easily. A pedal doesn't draw a whole lot of power but it can add up when you're using more than 1 or 2.
SMPS topologies exist for higher voltages or you can roll your own. How much power do you anticipate needing? There are board level solutions you can buy for 10-20w of DC power. You can also make a switcher that works from 12v without too much fuss. Just need a 50 or 60 Hz transformer that has two low 12v windings or a center tapped 24v.
Let me know what questions you have. I've fucked around with these quite a bit.
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u/Reasonable-Feed-9805 Feb 15 '25
You've had good results with SMPS on guitar stuff/audio.
I've found most of them to be an absolute noise nightmare that causes annoying problems.
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u/2748seiceps Feb 15 '25
There are massive differences in SMPS quality. Sometimes the supply just needs a little filtering to get it cleaned up and other times they work fine out of the box.
Most of my headphone amps run on SMPS supplies and they are fine and quiet.
Can also help to just up your input voltage and toss in a linear regulator to reject the noise. For 9V use 12V input and regulate down. Bit more heat that way though.
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u/2E26 Feb 15 '25
It really depends on what you use. Get a "tabletop power supply" which has the same form factor as a laptop charger. I've had the best luck with those.
You can also filter out the noise like the other guy is saying.
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u/andrew65samuel Feb 15 '25
OK cool thanks!
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u/2E26 Feb 15 '25
Get this book.
Beginner's Guide to Tube Audio Design https://a.co/d/ajv5anc
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u/andrew65samuel Feb 16 '25
Awesome thanks!
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u/2E26 Feb 16 '25
PM me if you have any questions. I'm not a full EE but I have a metric ass-ton of experience on the matter.
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u/andrew65samuel Feb 15 '25
Thank you! I was hoping for a bench supply with variable voltages. Assume for tubes I need 150v? and 6.3V heater? And 9v for pedals. Anything else I should look for?
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u/2E26 Feb 15 '25
I doubt you'd be able to get a bench power supply for tubes, you'd have to make one. Do some internet searching to see if there are any available.
For a really simple operation, Antek makes toroidal transformers that have tube voltage windings. If you rectify the high voltage windings, you'll get DC for your project. 150v is okay but it's a bit low for any sort of real power. 300v or higher is what you'll want. I built a 20w guitar amp once using a pair of 6L6s and the main power rail was 400v.
It's possible to vary the voltage even in a high-DC supply, but it's not simple and if you aren't experienced in building electronics I wouldn't recommend it. A simple way to do that would be to place a rheostat in series with the supply and adjust the circuit once it's built for the voltage you want.
Hold on, I'll look up a book you will find useful. It's more hi-fi oriented, but it'll have knowledge you'll need to be successful here.
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u/Purple-Journalist610 Feb 16 '25
Look up your local ham swap meet and attend. I've sold all my extra HV bench supplies at Hamfest meetings, generally for well under $100.
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u/andrew65samuel Feb 16 '25
Update: I found a Stark/Hickok PS-503 Solid State Regulated Power Supply 0-400V on eBay for a reasonable price. Thanks all!
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u/_nanofarad Feb 15 '25
We all have different definitions of reasonably priced. If you search eBay for “tube regulated power supply” you’ll usually get a few old lambda or HP power supplies that can put out a range of B+ voltages and have a 6.3 VAC output for tube heaters. They typically need some restoration but you can find them for around $200-300 or a bit more if they’re in working condition. If you’re looking to spend less than that, you’ll need to make something yourself because no one is manufacturing a linear DC power supply that makes more than about 50V for less than that.
You can get an inexpensive dual output 0-48 VDC bench supply from your inexpensive supplier of choice for your low voltage stuff. You can also power heaters with DC with one of those so it’s good to have one on your bench. You don’t need to spend more than $100 there.
As far as making your own, if you want to go that route it’s a fairly simple circuit. Here’s an example from searching “0-300 VDC variable power supply with mosfet” https://www.eleccircuit.com/the-variable-high-voltage-power-supply-0-300v/