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Crazy Idea for an amp

Discussion in 'Amps and Cabs [BG]' started by bassman314, Mar 25, 2005.

  1. bassman314

    bassman314 I seem to be a verb, an evolutionary process...

    Mar 13, 2005
    Bay Area, CA
    ok, I need a small amp... preferably tube based with XLR outputs, as well as a small driver for use as a monitor/pre-amp for my AEB.

    I'd like to have it be battery operated , as well...

    So, I think I'll build it... Bass it off the old Fender Bassman 30 (I have the schematics for it)

    So my main questions:
    1) What voltage should the batter run at? I'm nothtinking I'm going to pop soe D-cells or 9volts.. I'm thinking a NiMH power cell. I know I will probably need some custom transformers to go from the battery voltage to the voltage levels of the tubes.

    2) I'll def. need to put a balancing transformer for the XLR. do I want to do that between pre-amp and power amp (before the phase splitter, I'd assume), or since I'm only running 30 watts, do I do it after the power stage before the speaker and just pad the output?

    3) I'm thinking of a 8-10" neo driver to save on weight. Should the cab portion be sealed? Ported?

    Any other thoughts?
  2. tplyons


    Apr 6, 2003
    Madison, NJ

    I think you're looking at something beyond technology. Battery powered tube amp? I think this is beyond what batteries can do man.
  3. Heh, the batteries would weigh more than the speaker cab. :scowl:
  4. Selta


    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    It can be done, but the weight of the battery would just be absurd. But really, what's the point? If you're looking for that small of an amp, why not just use headphones or something?

  5. Just use a car battery, should work ;)
  6. Happy MurphDay

    Happy MurphDay

    Mar 9, 2004
    I know that opinions are subjective, but I wouldn't consider a 8x10 small, maybe light(er) if neo drivers are used
  7. Any tube amp, operated off of D cells or 9 volt batteries, would drain the batteries in no time flat.

    I've drained a car battery with a small tube amp (and an inverter) in less than an hour.

    The "original" tube-operated devices, developed in the early part of the 20th century, ran entirely off of batteries. But this was completely impractical, since you need hundreds of volts DC to power the tubes. So very early on they developed how to run tube amps off of AC....

    I hate to throw a wet blanket on your creativity but from a technical viewpoint, this isn't really practical. You need to convert a few volts DC to lots of volts (hundreds) DC, and DC to DC conversion (at these higher voltage levels) isn't really something you want to try at home. :eek:

    Transformers won't work on DC, so you either have to a) convert the DC to AC, then transform it up, then rectify it/filter it back to DC, which ain't efficient; or b) do this with some pretty fancy circuitry. :eek: :eek:

    Out of curiosity, what level of training have you had in electronics?
  8. bassman314

    bassman314 I seem to be a verb, an evolutionary process...

    Mar 13, 2005
    Bay Area, CA
    no no... *L* 8 -OR- 10" drivers.. single speaker.. hence why it's only 30 watts.

    I know the battery will quite a bit... Part of the reason I want to do this is so I have a small amp that I can use in situations where power isn't always readilly available.

    I also want to do it, just to see if it can be done *L* crazy engineers.
  9. Aerolithe


    Jan 23, 2005
    Columbia, MO
    As mentioned, you can't use a transformer with DC, but I thought I'd mention that converting DC to AC and back to DC isn't something you want to even think about doing, and you'd probably lose a lot of power in the process. I'd say batteries are going to be more trouble than they are worth.

    Also, I haven't seen the schematics for a Bassman 30, but you may want to keep it simple if this is your first project. No one is really going to be able to help you with that, you may want to look for some DIY audio/amp sites and use some of their designs (www.ax84.com does guitar tube amps) so there are plenty of resources available.

    Edit: If you are willing to use transistors, battery power might be an option.
  10. dood


    Dec 9, 2004
    yes, it is possible, but agree that it would drain batteries very quickly.

    However, I do have schematic diagrams for various preamp circuits that use a wee bit of clever technology to ramp up 12volt DC to 180v , with just enough current to run a couple of valves. For how long on batteries I'm not sure, but they are designed to work on a 12v wall wart. Not enough current to run a power amp tho!!

    Good luck with your project.

  11. bassman314

    bassman314 I seem to be a verb, an evolutionary process...

    Mar 13, 2005
    Bay Area, CA
    several college courses and interest, mainly... I've fixed up a couple of tube amps and several effects pedals.. I've built a couple of AC-DC power supplies... This would very easilly be my most ambitious project to date.

    *L* looks like this is a plan that is going out the window.. no worries... better to come up with a crazy idea, and discard without hurting myself...

    I'll build it with just AC, add in the XLR out, and then get a pignose or something for battery power.. I know they make a small battery operated amp for keyboard/bass.
  12. Dude! Run if off of solar power. Nine or ten acres of solar panels might do it. :D
  13. bassman314

    bassman314 I seem to be a verb, an evolutionary process...

    Mar 13, 2005
    Bay Area, CA
    actually *LMAO* I'd do one better... ue the "Midnight sun" system my college developed for the DOT and the Military...

    TPV -- Fun at night

    Enough of these, and MAYBE we can do it!!! PORTABLE TUBE AMPS, HERE WE COME!!!! :hyper:

    ok not really *L* it still provides DC power, and I doubt it would still devlope the 100-200 volts I'd need.
  14. To date Western Washington University has achieved 900 Watts from a single burner with an efficiency of 7%.

    Whoa! The gas mileage ain't so good is it?
  15. bassman314

    bassman314 I seem to be a verb, an evolutionary process...

    Mar 13, 2005
    Bay Area, CA
    seeing as an internal combustion engine is 13%? not that far off are they... :D
  16. Joe P

    Joe P

    Jul 15, 2004
    Milwaukee, WI
    I have to run at the moment, but if it's a crazy engineer thing just to see if you can, then I'll say that you definately can!

    The voltages you need are no problem, with the modern DC-DC switching inverters - and they're quite efficient.

    Tubes - mainly because of the filiments - are not. It definately would go through battery juice.

  17. notanaggie

    notanaggie Guest

    Sep 30, 2003
    Man....this is SOOOOOOOO ironic, I can barely STAND it...


    Seeing as how you nabbed the Electroharmonix symbol (or something close) as your pic, YOU of all people should oughtta know........

    ALL SAY it OUT LOUD, class............

    ................MIKE MATTHEWS FREEDOM AMP....................

    Now as to it being practical, well, maybe not as practical as it might have been, but it worked.

    For more modern stuff along the small battery amp lines, check out ZVEX. I forget their website, but he has a cool little TUBE guitar amp about the size of 4 cigarette packs, (100s). Sounds pretty cool thru a 4-12 cab. For bass, well, swipe the idea, maybe..
  18. Even at 100% efficiency, supplying 30W out of batteries for any length of time would require pretty big batteries.

    Now figure that solid state amps aren't nearly 100% efficient.

    You need to convert the DC to a higher voltage, that won't be efficient either.

    The tubes create tons of heat. Where does the energy to produce that heat come from? The batteries.

    Combine the voltage converter, waste heat from the tubes, wasted energy in the amp circuits, you'll be lucky if its 50% efficient, which I think is probably not possible. So your batteries would have to put out 60 watts to create 30 watts of music. They won't last long. Or they'll be big, bulky, and heavy.

  19. The most efficient amp I'm aware of is a class D. D for digital. They are microscopic in comparison to a class a, a/b or b amp and they still don't use the power that even a class c does.

    A class d the size of a credit card with a single 10,000uf cap and a small toroidial can produce 500WRMS on a tiny heatsink as they are over 90% efficient. Almost no heat, all power and thesedays the thd is very small considering the pros.

    They are also very simple to build.

    They are used heaps now in small appliances like small souround amps as 5or 7 channels will fit in small spaces.

    You could use one of these that is 30-50watts and at least that battery power would go out as sound and not heat into a heatsink.

    As for the valve pre amp. As I understand, valves use very high voltage but very low current. I think the problem is the heater. Maybe a transistor preamp with a tube amp simulator in the way of an effects preamp may be more practicle.

    The battery, lithium polymers are very light, heaps of grunt, small space. Very expensive. Doh.

    Given the use of these techs I can't see a reason why it wouldn't work. Just the valve thing may be a killer on power.

    food for thought????

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