Crawls Backward (When Alarmed)

IconProjects, musings about guitar builds, guitar repairs, vintage tube amplifiers, old radios, travel, home renovation, and other stuff.

CMoyBB Headphone Amp DIY Finished!

I told you this was going to be a quick project. Took just a couple hours.

With the board wired and the amp working, it's on to the 'cabinet.' It's actually a Altoids mint tin! There's a mini-cult of folks building electronic junk into mint tins, so this is just one more.  I was attracted to the idea of having the amp be small enough to put in my pocket on my commute.

Before I start the tin, I cleaned off the bottom of the PC board with isopropyl alcohol.  This is the real deal - 99.953% pure.  I have a 100ml (4.5 fl oz) bottle that set me back $8.50 (€ 6.22)! That's $1.89 an ounce, 8.5 cents a milliliter or .06 Euros a milliliter. Not cheap no matter how you look at it.

I originally bought the stuff for some DIY record cleaner I have yet to brew up.   Too many projects.

The JDS instructions include a nice layout template for punching the holes for the jacks and LED.  They suggest using a paper hole punch to punch them out.  I was in the Despot and bought a leather/fabric/cardboard punch thinking it would do the job.

It did not.  Not sharp enough to make an initial cut.

Rather than go out and get a hole punch, I decided to try Plan B.

In Plan B, we drill the holes.  This more or less worked, but it didn't make clean holes, and it dented the tin a tiny bit.  But it's close enough for prototyping. 

I also misjudged the height of the holes by a couple of mm, so I wound up filing them to fit.  Even then they're a bit too high for my liking.  I may wind up using another tin at some point. 

But the proof is in the concept, as they say, so I pressed on regardless.

Here's the finished amp.  Crazy, huh? 

For some reason, the input and output jacks didn't come with nuts, so I need to source them.

It's also an extremely tight fit with 2 batteries in it.  JDS suggests using 'economy' flexible 9v connectors.  I'm using some nice heavy duty ones.   The batteries to fit a bit less snugly without the bigger connectors - so I'll change those out.

 The circuit is nice in that the volume control has an on-off switch, but it's wired through the output jack.  So if the switch is on, the amp doesn't go on unless there's a plug in the output.

It sounds amazing.  Way more fidelity that just the Sansa clip.  And actual imaging and far better stereo separation!  I took it on a test run yesterday and did discover that my goofy capacitor hookup is a bit wonky, so I need to rethink that.

I wondered how the amp could improve the fidelity of the original signal - but it does.  It's really astounding.


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