Ying Yang Gear

Tao Ex Machina

The Way from a machine

Project blog by Tim Heath

Let us think the unthinkable, let us do the undoable,
let us prepare to grapple with the ineffable itself
and see if we may not eff it after all -Douglas Adams


New DFM! Same great taste!

The "Sound Producing Amplifier Module" or "S.P.A.M." is hitting that point in it's life cycle where I can't really dedicate enough time to fufil orders, and still solder them all by hand. A good problem, to be sure. So as we hop from revision 5 straight to revision 7, I'm looking towards Designing For Manufacture. In the case of this amp, that means moving to mostly surface mount components.

I was mildly nervous that different tolerances and characteristics of surface mount components would affect the performance of the amplifier. Looking back, this is a silly thought. I made careful selection of components with all the same values. So despite the packaging, nothing really changed. Still, I felt it worth comparing the new prototype with the old rev.

I put put both amps on the bench, and hooked up an HP-35660a dynamic signal analyzer. There is about a 5db change in response from 64Hz to 1000Hz. Above 1000Hz the test goes a bit crazy, but all still within 10db. As you can see from the photos, the two amplifiers perform almost identically. I'm not really sure why I expected to see any difference, but I feel good to have gone through the effort.