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?
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?
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.
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.
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 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
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