Icepower 200ASC aux 12vdc output for preamp?

Can the 12vdc .4A aux output of the Icepower 200ASC power a fender style 2 stage 12ax7 preamp?
Considering a build similar to the Milkman the Amp 100 pedal. Looks like a class D with a tube preamp and a couple of effects boards. Wondering if the preamp or effects are running off the aux output or their own psu? Any ideas?
 
A 12AX7 at 12.6V needs 0.15A, so that part can work. Next you need a switching power supply to get the high voltage. Some people used a dumb 555 chip and mosfet to get it, others a real switcher chip. And then there are the ready made modules you can buy online.


Short answer, yes.
 
You might just have pushed pe in the direction of making a little tube/Class D amp. I was planing on one with some bells and whistles, might do one rather stripped down. While trying to figure out a body for a headless practice electric guitar I moved over some cigar boxes, being easily distracted as a squirrel I picked up one and thought, "I think the stuff could fit in here." Stripped off the labels and put it aside, I am working on the guitar today after all.
 
A 12AX7 at 12.6V needs 0.15A, so that part can work. Next you need a switching power supply to get the high voltage. Some people used a dumb 555 chip and mosfet to get it, others a real switcher chip. And then there are the ready made modules you can buy online.


Short answer, yes.

Not when the tubes are cold. Current draw will be probably 2-3x nominal. A properly designed switchmode will do a safety shutdown/restart loop. It may eventually turn on, or it may not. I've seen this with switchmodes before. I have one amp with a 4a switcher that barely starts a 1.5a nominal heater string.
 
Not when the tubes are cold. Current draw will be probably 2-3x nominal. A properly designed switchmode will do a safety shutdown/restart loop. It may eventually turn on, or it may not. I've seen this with switchmodes before. I have one amp with a 4a switcher that barely starts a 1.5a nominal heater string.


Seems I have had better luck than you. If you are talking a wallwart from EBay on 120V, they only put out half their rated current, Bump up the supply voltage and they produce more. I think they design them for 220V. I derate them under normal conditions, name brand equipment have all put out their rated current on 120V. I have used a few of these in guitar amps and had no issues.For a 1-2 tube preamp I would not be concerned.
 
Can the 12vdc .4A aux output of the Icepower 200ASC power a fender style 2 stage 12ax7 preamp?
Well, you got one "No!" and one "Yes!", so I'll go ahead and give you a "Maybe!" to complete the confusion. :)

Here's the thing: Your Icepower module's 12 V output is only rated for 4.8 watts output. A single 12AX7 heater needs needs almost 2 watts (1.9 watts if the spec-sheet was gospel, but it never is.)

That leaves you with less than three watts to feed the small switching circuit that's going to produce the B+ voltage for your 12AX7. The 12AX7 typically will draw 2 - 3 milliamps at, say, 300 volts, which is 0.6 to 0.9 watts. You need a switcher that can spit out a watt at 300 volts while drawing less than 3 watts.

So if you can find an efficient, very low-power boost switcher to generate your B+, on paper you can just about do it, with almost no safety margin, and by pushing your expensive Icepower module's 12V auxilliary output to nearly its limit.

But why walk a tight-rope, and risk damage to the costly Icepower doodad, when a separate 12V switching power supply can be bought for very little? You may even have a suitable one lying around.

I know it will be more work to have a separate supply, but it sounds as though you're going to be doing a fair bit of DIY anyway.

With a separate 12V DC power supply, and a boost converter such as this one ( https://www.amazon.com/Cuawan-Volta...words=390v+boost+mobile&qid=1581194692&sr=8-1 ), you should be able to build what you're planning.


-Gnobuddy
 
I would always worry that those switching supplies would emanate so much RF noise that would get into the rest of the circuitry.
I do recall that Tubelab (George) mentioned a project he'd encountered where two switching supplies interacted in a bad way, producing a beat frequency that was in the audible range, and making nasty noises in the speaker as a result.

I worried about these sorts of problems quite a bit a few years ago, but have been reassured by actually trying somewhat similar things a few times since then. Maybe I've been lucky, but I haven't encountered any problems at all.

One example: a current project uses one switching power supply for a class D power amplifier board, a second switching power supply for a little Yamaha audio mixer connected to the amp, and a third switching power supply feeding a fourth digital (switching!) guitar reverb pedal. I have been able to happily chain all of these with no detectable bad side effects.

-Gnobuddy