1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Thinking of DIY micro amp...

Discussion in 'Amps and Cabs [BG]' started by paintandsk8, Jan 24, 2008.


  1. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    I'm junior studying electrical engineering at Purdue University. The time has come for me to start proposing senior project ideas. We have to design and build some electronic device of reasonable complexity from the ground up, with lots of documentation along the way.

    One of my ideas is to make a true micro amp. The idea would be to fit at least 100W into a package maybe an 1.5"tall x 3" x 4". The real kicker would be that it would have no onboard controls! The amp would be specifically designed to work with the J-retro preamp in my Lakland. The amp itself would most likely have nothing but a mini-toggle for mute. So, the basic idea would be a tiny black box, small enough to fit in your bass case, with not much more than an input and an output.

    Don't get your hopes up about this happening any time soon though. I'm just in the thinking out loud stage, and I have to propose at least 3 projects. Thoughts?
     
  2. Jared92

    Jared92

    Nov 1, 2007
    Fairfax VA
    Sounds great. Just last night i was thinkin how i really wanted to make my own protable speaker. out of a 5 " but. then i thought id need an amp for that. or at least a way to battery power that, and i dont know how. :crying:

    But your idea sounds great!
     
  3. Nick Kay

    Nick Kay

    Jul 26, 2007
    Toronto, Ontario
    How are you going to stick a 100w power amp in a box that's smaller than BOSS pedal? I don't care if you use an SMPS with a Class D output section, that seems damn near impossible to me. Hell, even the Crate Powerblock was 3"x10"x5" or something around there.
     
  4. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    It will definitely be Class D with an "off-line" switching power supply, almost all surface mount components. I've seen 240W in about 2-3 cubic inches. That was without a power supply. Those dimensions are an approximate goal, it could end up a little bigger. I've spoken with a very respected professor specializing in audio and he confirmed that something on that order of magnitude was very possible.
     
  5. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    I like miniaturization. But I hate wall warts and line lumps. And how small is the amp really, if you have offloaded the power supply from its casement, but the user still has to deal with the additional clunky thing?
     
  6. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    I never said the power supply would be separate. I'm definitely planning to keep the power supply onboard if at all possible.
     
  7. grovest

    grovest

    Feb 26, 2002
    I think you can be more ambitious. Is the 'no controls' really a benefit or more akin to 'value engineering'? A simple compact amp could be bought by any schmo from Mouser with two mouse clicks. I do think that creating a bass amp is a winner of an idea, from many angles. I'd add some kind of eq, or maybe eye-candy like a spectrum display, or what about a display that records the rhythm of your playing, and maybe interacts with it in some visual way, or some feedback from power draw, what about sensing proximity to a rear wall, and automatically eqing in relation to distance, or x y z ??? Go wild, I'd say.

    Good luck.
     
  8. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    I think it is a good learning project. Since I am not a real engineer, I have watched the development of Class D from the sidelines. It seems to be at least 10x more difficult than Class-AB. Browsing the www.diyaudio.com Class-D forum has convinced me that it's far from a trivial exercise. The basic design concept is simple, but it becomes real engineering due to parasitics, layout, and protection issues.

    Please share a link to your final report when you get to that point! Meanwhile, your first step is to find out who has a really fast digital scope that you can use.
     
  9. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Well spoken, fdeck. If it was easy, there'd be a lot more good mini amp or lightweight single rack unit examples around now that there is some market impetus.
     
  10. this sound quite cool. The course you are doing is probably quite similar to what I want to do in 18 months when I head off to university. The concept sounds great but I think the controless form might make it a little impractical if you were ever to try and gigs with it.
    Best of luck
    Dan
     
  11. Tristan

    Tristan

    Jan 28, 2001
    Ottawa, Canada
    just rebox a smokey amp
     
  12. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    paintandsk8 already said that his bass's pre would supply all needed control. In other words, the input specs of the power amp would be closely matched to the output specs of the J Retro.
     
  13. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    Thanks for the link, I'll be sure to do some reading there. This is certainly an ambitious project, a few students have had success with class D amps in the last few years so that is encouraging. I think the Tek scopes in the RF lab are good up to about 350MHz, so I should be good there.;)
     
  14. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    Exactly, this is going to be a very purpose built project, specifically for use in my setup. That is what is going to allow me to make this thing simple and ultra compact. I won't be held to the market requirements and flexibility that limits what the big guys can do. There are all kinds of gimmicks and bells and whistles I could do, and I've thought about doing a simpler amp design and adding all kinds of crazy functionality, but the gimmick here is that there aren't any gimmicks. Do one thing, and do it well, as compactly and efficiently as possible.
     
  15. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Actually though, such an amp would work with a LOT of active onboard preamps : }
     
  16. 4StringTheorist

    4StringTheorist Supporting Member

    This sounds fascinating! I wish you luck, and please keep us updated on this.

    I graduated from Purdue in Dec. 2003 with one of my degrees being in Physics. While I was there before your time, I was once one of the T.A.s presiding over the Freshman gauntlet that is PHYS 152.

    I also was one of about 4 undergrads who spent a summer coding the (then) new Giambattista et. al textbook problems into CHiP.

    You're welcome. ;)

    Keep the low notes loud and proud, Boilermaker.
     
  17. Handyman

    Handyman

    Sep 4, 2007
    Austin, TX
    Here are a few things to think about:

    - Working with surface mount components is a rather tedious and unforgiving activity. Make sure you or someone you work with has access to a really good soldering station, a very steady hand, and lots of patience.

    - Design of both switching power supplies and class D amplifiers can be very unforgiving. Use ICs with as much integration as you possibly can to cut down on design time, board space, and potential for error. Every bit of design that's already integrated into an IC is work you don't have to do yourself.

    - Take a look at mostly-integrated class D amplifiers such as the AD1994 (up to 50W from a single IC, really impressive). Tripath also make some really impressive amplifier modules, though I don't know what their status is with their bankruptcy.
     
  18. asad137

    asad137

    Jan 18, 2007
    Minneapolis
    Physicist
    While I agree with both of these sentiments in general, I'm not sure they're appropriate for someone doing a senior EE project where they have to build something from the ground up. I'm not sure stringing together a bunch of integrated IC's to a pre-existing class-d module is in the spirit of the project.

    Asad
     
  19. Actually, with an amp that size, you could integrate it right into a speaker cabinet.
     
  20. Flintlock

    Flintlock

    Jul 3, 2007
    Southampton
    Do one better, make it a tube amplifier!!

    Zvex have done the same thing for guitar: http://zvexamps.com/
     
  21. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 17, 2021

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.