regualted 12 power supply question

[beasleybodyshop]

Hey folks, i this cool looking discrete power supply yesterday attached to an old exhibit at work. It puts out 12vDC at 8 amps, and it has two separate 12V taps. the voltage adjustment will only dial it down to 11V and up to 13V.

Any way I could use this to discretely power filaments in a high gain build? Its small enough to stash in a chassis - about 2.5 inches wide, 4.5 inches long.

EDIT - pic attached

[Leo_Gnardo]

"Switching supply" like what's in computers. Some people like 'em. There's the possibility of the switching frequency showing up in your audio, as a high pitched whine. Oh that's the neighbor, she wants you to turn it down.

There are 6V switchers, or anything you want. OTOH it's easy enough to use solid state regulators on an otherwise traditional power supply, no switching noises there. One of the problems with running filaments off either, is that current jolt that happens when you start up filaments from cold. I find it's typical to see about 6 times the normal current draw on startup. If your supply is tuff enuff, no problem. If not, youl'll find yourself faffing with regulator transistor replacements way too often, or worse trying to decipher what's going on in a switching supply & trying to fix that. "It's simple and it works" is a good reason most stick to running the fil's straight off the winding.

[beasleybodyshop]

Thanks Leo. Now what in the hell can I use it for?

[M Fowler]

Powering a Class D amp module.

[jazbo8]

Most of the modern SMPS use pretty high switching frequencies (say 40-100kHz), so they are un-likely to be audible, especially in geetar amps. I built an amp (albeit not high gain) with 12V for the filament and 12V-300V DC-DC converter for the HV, and there was no detectable buzz/noise, but YMMV... As for the in-rush current on the filaments, it depends on the SMPS' design, many of them have short-circuit protection built-in, again, I had no issue with mine...

[Cliff Schecht]

Most of the modern SMPS use pretty high switching frequencies (say 40-100kHz), so they are un-likely to be audible, especially in geetar amps. I built an amp (albeit not high gain) with 12V for the filament and 12V-300V DC-DC converter for the HV, and there was no detectable buzz/noise, but YMMV... As for the in-rush current on the filaments, it depends on the SMPS' design, many of them have short-circuit protection built-in, again, I had no issue with mine...

Most off-line switchers like the one above operate at 133kHz. There's a very specific reason for this that involves a few different tradeoffs (EMI, filtering said EMI, magnetics size for a given current level, etc..). Whine won't be an issue unless the circuit or power supply itself is malfunctioning (sub-oscillations or pulse skipping at light load). If a "minimum" load isn't attached already, you can add one to keep things from ever malfunctioning (some switchers HATE being under-loaded).

Thing is, I find DC heaters to be an unnecessary complication a majority of the time. A properly wired and laid out amp is just as quiet. I also don't like running pure DC on my hard to replace vintage tubes. The theory I've heard is that the heaters develop "hot spots" when you feed them pure DC and this can cause them to fail prematurely (think about DC on a lightbulb instead of AC). I think the topic is arguable at preamp tube power levels, but not worth risking my babies!!

[jazbo8]

Thing is, I find DC heaters to be an unnecessary complication a majority of the time. A properly wired and laid out amp is just as quiet.

+1, DC heating is really meant for low-noise applicaitons like mic-preamp and phono preamp, it really isn't necessary in a relatively high noise application like guitar amp. My build was mainly to prove a point to myself, that switching noise from SMPS isn't really an issue unless they are poorly designed, and that I could make a super light-weight tube amp

[Cliff Schecht]

Don't get me wrong, I love the idea of switchers with tubes. Just don't like DC in preamps where it isn't needed as a general rule. Takes a lot of gain to get to the point where good lead dress won't get you by and I don't necessarily like things to get that complicated/gainy. At that point might as well as get a solid state power amp, the PI/power amp section aren't contributing anything "warmer" to the bees in a box tone.

I've been toying with an idea that eliminates electrolytic caps completely but doesn't squash the effects that the xfrm/rectifier/cap have. Sounds interesting enough huh? I need to run some sims before I go into too many details and that idea is a thread in itself. More of a fun theoretical idea, unless you plan on making some battery powered tube amps .

[beasleybodyshop]

Thanks everyone for the knowledge. I think i might try to make this into a pedal power supply for my board.

[eniam rognab]

Thanks everyone for the knowledge. I think i might try to make this into a pedal power supply for my board.

hey, thats a great idea!