[ST] Portable Amplification (long)

["Nathan Maher" <nate@xxxxxxxxxx>]

ST'ers,

The topic of using headphones, various comm. devices and even cell phones
has come up at least a couple of times during the last few years so I
thought I'd put in what may be some new information and offer up a service
to the list.  It seems that oftentimes people have trouble achieving
adequate listening levels from various portable devices while on a
motorcycle.  While I do not endorse any activity that could lead to hearing
damage boosting the signal a bit could be the answer.  As a side benefit the
use of a separate amplifier greatly improves the sound of any headphone (at
least in my experience).

What I propose to offer is what is commonly known as the Chu Moy headphone
amplifier.  It is a common design, people sell them on Ebay and commonly
house them in Altoids mint tins.  Professionally built examples start around
$100.  Ebay examples typically sell for between $40 and $60 depending on
options like volume control etc.  If right now you're saying what the heck
is a headphone amplifier that's ok, either google Chu Moy and do some
reading or hit delete.  I'm trying to keep this as short as possible :).

While the novelty of the mint-tin case is undeniably cool they don't wear so
well and offer very little in the way of moisture or impact resistance.
I've built 4 examples like this during the past three months and started
modifying the design to better suit my personal preferences.  Over the next
couple of months I'm going to be building a few examples of this modified
amplifier housed in a much more rugged semi-sealed plastic enclosure that I
think would work pretty well for the motorcycle crowd.  I have no intentions
of making any sort of career out of this but if folks were interested I
could probably be coerced into building a few for folks.  Please understand
that it takes 8 to 10hrs to build one of these and somewhere in the
neighborhood of $40 in parts (for my configuration anyway) so that if I sold
them the price would probably be around $60.  I'd be paying myself a
whopping $2.50 an hour!  But like I said, I build these for fun, not for any
real profit.

So the features of my amps would include:  Full volume control, on/off
switch, lighted power LED, single 9v power supply, true dual voltage split,
standard 3.5mm stereo input and output and a professionally built plastic
enclosure w/ 9v battery door for easy replacement.  Run time is around 30 to
40hrs w/ the single 9v.  The electronic components that will be used
(resistors, capacitors, opamps, etc.) are pretty much the uniformly accepted
values (tweaked a bit) and if you want hear the details on that I'd be happy
to share.  I'd imagine that most liSTers have hit the delete key by now
anyway so I'll wrap this up.

I've been using one of the mint-tin amps that I built for the past couple of
months with my Etymotic Er4p's and the difference with and without the amp
is nothing short of amazing.  I've also used them with my home headphones
(Sennheiser HD535's and HD580's) with similar results.

So, if you want more information or are interested in more details about the
amps feel free to drop me an email.  I can link to pictures of two of the
amps that I've built so you get a better idea of what goes into the
construction.

If you're lucky enough to be riding keep the rubber side down and the shiny
side up.  I'm stuck in the midst of a good size snow storm right now
:shrug:.

Nate
00SprintRS




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