Crawls Backward (When Alarmed)

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Noisy Cricket Amp Build Done - It Becomes "Amp 386"

I was able to wrap up the mini-amp last night.  It's based on the Noisy Cricket, but I revised the circuit somewhat, so I'm inclined to just think of it as "Amp 386."  For now.

Used a Radio Shack project box to put it in.  Ultimately, the amp will go into the 'cab' that Toy Making Dad is cooking up.  But I still need to put it into something for field testing and delivery to the TMD Workshop.

I marked up a layout and drilled the panel for the pots and switch.

I keep forgetting how easily these cheap inexpensive aluminum panels bend.  Even drilling them makes them a little wonky.

One new tool I scored at Rat Shack was a set of nibblers.  I was reading a thread about them on the Antique Radio Forums.  Almost bought a more heavy-duty set, but I read that the RS version isn't too bad, so I picked one up.

Very useful to, well, nibble metal on this kind of chassis.  I wound up cutting the main speaker hole with my jigsaw, but the nibblers came in handy for some trimming.

Mounted up the components onto the panel/chassis.

The leads are awful I know.  If this was the final destination, I'd trim them and make them tidy.  But I don't know what the final product will look like, so I left them long deliberately.  Not like anybody will see it anyway.

The speaker is a 3" 3.2 ohm radio speaker.  I tested about 10 (!) little radio speakers and this was the winner.  I had a 4" that sounded dynamite, but it wouldn't have left enough space on the panel to mount the controls.

I put some speaker damping stuffing material in the box.  I figured it couldn't hurt. 

You can also see the wiring to the speaker output and power input jacks.  The amp can run on the internal speaker, or you can plug it into a proper guitar cabinet.  I'm running it on a 9 volt battery now, but there's an input for a wall wort.  The 386 chip can run on up to 18 volts.  (Bwhahahahaha).

All buttoned up, and some knobs stuck on.

It's not perfect, but it will suffice for a prototype/test/demo amp.

The controls are for volume, tone and gain.  I tried the Noisy Cricket 'grit' switch and left it off.  It really just adds noise - no gain.  I changed the tone circuit to the 'Stupidly Simple Tone Control' from Jack Orman.  It's a great tone control.  It's flat in the middle, rolls off highs rotating it one way, and boosts highs the other.  Really nice.

The grill cloth is Fender Oxblood-style.

The speaker out and the DC input.

I see more experiments coming up.  I'm running an LM386-1 chip now, and it's not loud at all (which is probably a good thing for a practice amp).  I'm going to try a 386-3 and -4 to see how much volume difference I get.  And I want to try running it on higher voltage. 




 
 
 
 

Post a Comment 2 comments:

  • Anonymous said...
    June 15, 2014 at 3:02 PM
    Nice project! Still playing it? Could you be specific about which of Jack Orman's tone control designs you used? I don't see any "Stupidly Simple" ones, just Stupidly Wonderful, and there are at least 3 of those!
    http://www.muzique.com/lab/swtc.htm has 2 in addition to the original by Mark Hammer
    http://www.muzique.com/lab/swtc3.htm has another, with variation for frequency range

    Thanks,
    CW
  • Yr Fthfl Blggr said...
    June 24, 2014 at 3:18 PM
    Hi -

    I used the third schematic on Jack's page. Sorry I called it the wrong thing...I think "Stupidly Simple" was just stuck in my head!

    The amp is now with my buddy, Toy Making Dad (see my links). He's putting it in some kind of fancy cabinet.

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