Is this OK for a heater supply?

[blacklight]

Hey all. I just modeled a a heater supply for my Aikido headphone amp. It's pretty much a result of my neanderthal thinking. My mains AC doesn't swing a whole lot so I don't think a regulated supply is absolutely necessary. Anyway, would you call this idea stupid? What should I do differently?

 

[SY]

It strikes me that this is more complicated/expensive than a regulator. Additionally, you'll want to take care of common mode noise as long as you're going to all this trouble.

 

[blacklight]

Nah, I just happen to have all this stuff available from my junk box. But yes, I did think it may be smarter to just built a regulator circuit. I've never dealt with DC heaters before, so I'm a little lost here.

 

[SY]

An LM317 will work wonders.LM350 if you've got unusually high current demands.

 

[alexmoose]

what voltage are those heaters operatring at? it seems like at heater voltages, you can use FAR larger capacitances than 330uf

 

[rdf]

Aren't you dissipating >280 watts in the drop-down resistors? 2.6 amps through 41.5 ohms. Buy heatsinks.

 

[Wavebourn]

I'd use a bridge rectifier, 4,700 mkF cap, and this current limiting voltage stabilizer (12V Zener for 12.6V output, and a resistor in place of current source):

 

[blacklight]

Ah yes, seems like I didn't think ANYTHING while modeling that thing. Just forget that stupid picture. Thanks all. Back to Jones' books...

 

[rdf]

Nothing to get frustrated about, the only reason I saw it was from repetetive and explosive experience releasing the magic smoke from resistors. Now I always keep the solar calc on the bench.

 

[Sherman]

I just built a regulated DC filament supply for a hybrid amp I'm working on. Four 1N4007s,1 100uF 25V electrolytic, 1 LM317, 2 resistors (1/2W). Total cost (since I have about 10 LM317s here I got for twelve cents each) about $3.50 US. The perfboard I mounted it on is about 1/3 of the cost.

I'm thinking about making PC boards to use the LM350 per SY's suggestion for amps needing more than 1.5A of heater current. Also it would be easy to use a 12.6VAC source for both 12.6V and 6.3V heaters just by adding one more LM350 (or 317) and two more resistors.