More voltage from the 555 smps

[stinkfeet]

Hi! I'm a huge fan of the 555 smps design for its low noise and low cost, but I was wondering if there would be a good way to get more voltage out of it. For the really high-gain stuff I've been building, extra high voltages have been beneficial, but my smps has been maxing out at 370v with 3 12AX7s, and for the Mesa MKIII blue stripe preamp I'm looking to build soon-ish, I'm hoping to get around 430v. Right now, I'm using a 12V 5A Meanwell PSU; would more input voltage help, like the jump from 9v to 12v? I was thinking about jumping up to 18v and wiring the heaters in series, and also eliminating the need for the 6v regulator for the 3-tube build when I use 6n2ps, but I see that 18v is the absolute maximum for the 555. So that might not be a great idea. Are there any other mods I could do? I see that I'll want to upgrade to an IRF840 for the higher voltage rating if I can get it over 400v. I would not be opposed to using two 555 boards if it would give me the headroom I would need. Would I need to go to a flyback design for this much voltage, or could I make it work?

 

[vigilante398]

Higher input voltage can certainly help, but I definitely wouldn't recommend 18V into it. 18V is listed as the absolute max for NE555, but the stated operating max is 16V, so I wouldn't go higher than that.

As noted if you're looking to get over 400V, swapping out the MOSFET for something with more margin is a good idea. It's also a good idea to look for a larger inductor, you'll need something that can support the increased energy you're trying to get out of the circuit. 100uH is fine for smaller circuits at moderate voltages, but if you're trying to pull more out, you may want to look for a 220uH or larger inductor.

All of this is theoretical as I've never personally tried to get more than 350V out of an NE555 supply, and all the higher current stuff I do now uses a flyback supply.

 

[OkBoomer]

For the really high-gain stuff I've been building, extra high voltages have been beneficial, but my smps has been maxing out at 370v with 3 12AX7s, and for the Mesa MKIII blue stripe preamp I'm looking to build soon-ish, I'm hoping to get around 430v.

What name do you build under? That Mesa sounds interesting.

 

[stinkfeet]

Higher input voltage can certainly help, but I definitely wouldn't recommend 18V into it. 18V is listed as the absolute max for NE555, but the stated operating max is 16V, so I wouldn't go higher than that.

As noted if you're looking to get over 400V, swapping out the MOSFET for something with more margin is a good idea. It's also a good idea to look for a larger inductor, you'll need something that can support the increased energy you're trying to get out of the circuit. 100uH is fine for smaller circuits at moderate voltages, but if you're trying to pull more out, you may want to look for a 220uH or larger inductor.

All of this is theoretical as I've never personally tried to get more than 350V out of an NE555 supply, and all the higher current stuff I do now uses a flyback supply.

Thanks! I'll see what I can do with a bigger inductor; I'll probably just keep it at 12v since my 6n2ps draw way too much current for the regulators. Tayda doesn't happen to have a decent transformer for a flyback design, do they?

 

[stinkfeet]

What name do you build under? That Mesa sounds interesting.

I just do builds for myself, mostly just extremely budget builds. My last build was based on a Bret Guitierrez-modded Marshall that I thought had the same mod as Gary Holt's, but it turned out to be something different, still based on the Langner topology. I'm not a huge Mesa guy, but the pregain tone stack is really sweet for tone shaping, and the blue stripe being more aggressive than an IIC++ is very tempting. The transistor gyrator EQ makes things much easier too.