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Old 18th April 2008, 02:56 AM   #1
christw is offline christw  United States
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Default fun idea: cameras and tubes!

A while ago I was reading about someone making a tube amp from the waste of a disposable camera. I can't argue it'd be a fun idea, although I'm not sure where to start.

I kind of want to try and design a simple 1 or 2 tube design around the basics of one of the flash circuits of one of these cameras. Maybe I'd run it off of 2 parallel D cells to get some life out of the batteries. (I have one I picked up today to get myself in gear and I doubt a AAA would cut it.)

I don't expect a mass of volume, but something fun to play with and get me started building tube amps. Plus, a battery powered tube amp, cool or what? (I don't think a micro tube amp would cut it for me.)

Anyways, I'm kind of looking for some pointers and ideas. I know the components and why they're there, but not how the interact. I just kind of need to know how to put together a working amplifier out of this. It's a curse to be only 19 and born in the solid state era. Well, in the going backwards respect.

So I could use suggestions of how to pull this off and what kind of tubes would be a good idea. Keep in mind, this'll be a junker and a starter for me in building tube amps. (I own enough for my damn guitar though!) I have spare 6V6, 12AT7, 12AU7, 5Y3, and some more 12A's. I would've gone for a SE design, but that's over my head atm so basically, my on hand supply is 6V6 and a handful of 12A tubes.

Heck, do you guys think I could go with one of those 12AX pre + 12AU driver designs for such a thing?

Anyways, I'll quit talkin' so much and ask... ideas?
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Old 18th April 2008, 05:57 AM   #2
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Assuming you have 4 AA batteries together to make ~6v, your heaters are going to eat up 3.5 watts at least constantly. This may or may not drain your batteries quickly, depending on how many you have. You could use 8 batteries in paralell to gain more current capability (IE longer life.) Just tap off of the one or two batteries needed for the boost circuit. I would be concerned about how much current the charge pump can provide? It's only pulsed DC which charges a largish value cap ( typically 100uf 300v.)


I definatly don't think that it could supply a 6v6 at all. You don't need a 5y3 since you already have DC from the charge pump.
I think the most you could do is a paralelled 12AT7 into a 5k trans for ~ 2watts of power, with a 12ax7 on the input, even this is probably stressing the charge pump big time.

Maybe try to get ahold of some submini tubes or 1.5v tubes?

Right there with ya on the time period thing. BTW, 2 watts won't be "mass volume," but will still be dang loud into an 8" speaker or so. Gotta get ahold of an old one from a console or something for it to sound any decent with a guitar though.
I'm not sure I understand your comment about SE being "over your head," as you will probably need to do this type of topology in your amp... after all it is the simplist design there is.

http://www.ax84.com/static/corepower..._Schematic.pdf

Check that little guy out. Really simple, just add a standard fender pre in front of it using one 12ax7, or better yet the AX84 "P1" preamp.
http://www.ampwares.com/ffg/schem/champ_5f1_schem.gif

Standard fender preamp in front of the 6v6. Lower the cathode resistor on the first stage to 820 ohms and add 25uf bypass caps to each cathode and you will get some more gain.

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Old 18th April 2008, 11:08 AM   #3
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I once built a small amp with a 1S4,or 3S4 tube? (I forget) and a camera flash circuit. For the OPT I used a small audio output trans. salvaged from an old TV. I soldered a small speaker from an old pair of headphones right on the output transformer leads.
It worked pretty well!! It didn't get astronomically loud,but it was loud enough to fill the room with some sound.
I had the whole thing running from 2x AA's,for several hours that day.

Here's a start:
http://members.aol.com/sbench101/Bat...mps/3vHiFi.gif
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Old 18th April 2008, 10:18 PM   #4
christw is offline christw  United States
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I meant designing a full-fledged SE amp from the wall to the speaker was above me. It's why I was opting for a 1 or 2 tube circuit that would probably be based off of a preamp circuit and I have DC current already supplied, hence the wall reference. No need to work another transformer, the 5Y3, filter caps, or any of that into it. I was keeping it simple. I was hoping to just try something for a start even if it turns out poorly. :P

I haven't seen much on subminis as effective amplifiers at all though. All I've seen so far is a hearing aid-amp designed and built, but with a lack of serious power. It was something in the double digit milliamp range I believe.

Well, this is not accounting the Siegmund Muddy Buddy ( http://www.siegmundguitars.com/muddybuddy.html ) I just remembered. Isn't the Z. Vex run off of subminis too now that I think of it?

Maybe some old car stereo tubes could work too?

As for power, I do realize 2 watts is a sizable amount, especially when driven. I have two of those little 5 watt guitar amps (a Gibson GA-5 and one of the ever popular Valve Juniors) and they can kick some serious volume.

Digitaljunkie, I think it might've been one of your posts I'd seen when running through google that put this idea in my head. If it was you, I think the post I saw said 1U4 or 3 something?
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Old 18th April 2008, 11:05 PM   #5
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Ahh yea,Maybe it was a 1U4 I used..
It's been a few years,so I don't exactly remember.
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