mhamel
500+ Head-Fier
- Joined
- Jan 30, 2003
- Posts
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- 135
The MouseAmp!
Pictures at:
Mike's MouseAmp Page
Ok, so I did the CMoy in the Intel wireless base station enclosure ( http://www.richat.com/mhamel/photos/cmoy-v1/ )and it got me hooked on retrofitting fun enclosures. I figured the base station makes a good desktop amp, so why not use the matching wireless mouse to make a portable amp.
When I took the mouse out of the box, I realized it's got a great location for batteries already, but it was limited to using 3 AAAs. Not great for an op-amp based amplifier unless I used something like the AD823. I didn't have any of those around, and I wanted to experiment a bit, so I built a new design from the ground up based on the datasheet circuit for the National LM4881N. It's a 200mW headphone amp chip with decent specs and a nice low power requirement. It runs *great* off of a 4.5v single supply and when all was said and done sounds surprisingly good. Total current draw (including the LED) when playing at quite a loud volume is about 6-7mW according to my meter.
I thought about using a step-up regulator and using a stock CMoy design, a buffered CMoy using AD823s, or an A47 with dual AD823s, but I would need to make things a LOT smaller to fit all of that extra stuff. I still may give that a shot, but I'm pretty happy with it as-is for now.
The other thing I wanted to retain was the mouse wheel - but fit the volume pot into the case so that the wheel controls the volume. That was the most fun part of the project aside from the amp itself.
I briefly entertained the thought of building an on/off controller for the power and retaining the left mouse button function to handle that, but it would have used more power and probably too big to fit unless I tried to build it with surface mount parts. It also would have made it too easy to flip the amp on and off inadvertantly.
I broke a few of the "rules" for good sound, including electrolytic output coupling caps, but the goal here was to build something that first and foremost fit cleanly into this enclosure with its' size and power supply limitations, but still sounded reasonably good with decent runtime from the batteries.
The amp uses miniature 1uF film caps at the input, and I used Beyshlag metal fim resistors throughout. The electrolytics are a combination of things I had hanging around. The volume pot is also something I had a bag of hanging around that I picked up from a surplus shop - which is a good thing, since I went through 5 of them before I finally got the mounting design worked out to my liking.
It's still breaking-in, and I'm hoping the mids and highs mellow out a bit, but bass response is very good and full. Not as tight as the CMoy, but it seems to play deeper. The mids/highs on the CMoy are smoother and more laid back, but we'll see what happens after this has another 30-40 hours on it. So far it's got about 20 hours and still running strong on its' first set of batteries.
-Mike
Pictures at:
Mike's MouseAmp Page
Ok, so I did the CMoy in the Intel wireless base station enclosure ( http://www.richat.com/mhamel/photos/cmoy-v1/ )and it got me hooked on retrofitting fun enclosures. I figured the base station makes a good desktop amp, so why not use the matching wireless mouse to make a portable amp.
When I took the mouse out of the box, I realized it's got a great location for batteries already, but it was limited to using 3 AAAs. Not great for an op-amp based amplifier unless I used something like the AD823. I didn't have any of those around, and I wanted to experiment a bit, so I built a new design from the ground up based on the datasheet circuit for the National LM4881N. It's a 200mW headphone amp chip with decent specs and a nice low power requirement. It runs *great* off of a 4.5v single supply and when all was said and done sounds surprisingly good. Total current draw (including the LED) when playing at quite a loud volume is about 6-7mW according to my meter.
I thought about using a step-up regulator and using a stock CMoy design, a buffered CMoy using AD823s, or an A47 with dual AD823s, but I would need to make things a LOT smaller to fit all of that extra stuff. I still may give that a shot, but I'm pretty happy with it as-is for now.
The other thing I wanted to retain was the mouse wheel - but fit the volume pot into the case so that the wheel controls the volume. That was the most fun part of the project aside from the amp itself.
I briefly entertained the thought of building an on/off controller for the power and retaining the left mouse button function to handle that, but it would have used more power and probably too big to fit unless I tried to build it with surface mount parts. It also would have made it too easy to flip the amp on and off inadvertantly.
I broke a few of the "rules" for good sound, including electrolytic output coupling caps, but the goal here was to build something that first and foremost fit cleanly into this enclosure with its' size and power supply limitations, but still sounded reasonably good with decent runtime from the batteries.
The amp uses miniature 1uF film caps at the input, and I used Beyshlag metal fim resistors throughout. The electrolytics are a combination of things I had hanging around. The volume pot is also something I had a bag of hanging around that I picked up from a surplus shop - which is a good thing, since I went through 5 of them before I finally got the mounting design worked out to my liking.
It's still breaking-in, and I'm hoping the mids and highs mellow out a bit, but bass response is very good and full. Not as tight as the CMoy, but it seems to play deeper. The mids/highs on the CMoy are smoother and more laid back, but we'll see what happens after this has another 30-40 hours on it. So far it's got about 20 hours and still running strong on its' first set of batteries.
-Mike
