Ramsey UAM2 20W Audio Amplifier Module Kit | 
 enlarge | Brand: Ramsey
Buy New: $34.95
Rating:  1 reviews
Shipping Weight (lbs): 0.5
nv: Audio Output: 20W max
Signal/Noise: 102dB into 8 ohms
Total Harmonic Distortion: Less than 1%
Audio Input: Line level
Gain Adjust: 4 input gain settings
Protection: Auto short to ground shutdown, Auto short to Vcc shutdown, Auto short together shutdown, Auto thermal shutdown
Power Input: 8-18 VDC, 2.1mm connector, (18VDC for full rated output)
Dimensions: 2.6 square, 1.43 diameter
Availability: Usually ships in 1-2 business days
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| Features:
| • | 20 Watts from one SMT package! | | • | Super efficient Class D design! | | • | Super clean output! | | • | No heat/heatsink concerns! | | • | Electronic kit, assembly required |
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| Editorial Reviews:
Product Description
The UAM2 is probably the neatest audio kit to come along in quite a while! It uses the latest amplifier technology to bring you clear, crisp, high-power audio without any of the heat which is normally generated! This is what is called a class "D" amplifier, or as the media calls it, a "Digital" amplifier. Instead of operating like a classic class "A" or class "AB" amplifier which leaves transistors biased on all the time, losing energy whether they are producing audio or not, the class "D" amplifier only produces power into the load or your speaker! This means that a small SMT part can deliver a full 20 watts of power without getting so much as warm! YES, I said SMT or Surface Mount! Now you can install this amplifier right inside your speaker enclosures, or wherever this nifty kit will fit, without worrying about a heatsink! Just look at the specs! Unique board can be snapped out into a small circle to be double face tape mounted directly to the back of a speaker! This IS a Surface Mount (SMT) kit, so you will need fine tweezers, magnifier, and a decent fine tip soldering iron! See assorted tools and accessories on our site. If you need a good 18VDC power source, check out our SPS18 power supply. (Who ever thought of 20 watts in a single SMT device; I still remember fighting with vacuum tubes to get 20 watts!)
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| Customer Reviews:
Neat little amp January 3, 2010
Optimist (Kansas)
4 out of 4 found this review helpful
Just finished building this. Took about 2 hours (maybe less), and it worked as advertised. Ramsey did an excellent job all around. Here are a few comments to help you if you're thinking about getting one of these (which you obviously are if you're reading this;-)
First of all, the kit I received looks even better than the picture. The top of the board is now classic green soldermask, with white silkscreen printing. It also had nice gold coated pads (colorwise at least) to solder to, rather than the tinned look in the photo. It is a very high quality PC board.
The build went quite smoothly, but I confess that I have experience with surface-mount parts, and I have the proper tools (small-tip iron, small diameter solder, good tweezers, and optical aids). One nice thing is that the SSOP integrated circuit was already soldered. While this may disappoint you initially, it is essential - as the chip has 25 mil or less pitch on the pins, and would be virtually impossible to solder well without a microscope, etc.
All the other parts you have to install/solder yourself. This is a good learning project if you are new to surface mount soldering - BUT - be very careful. Read the manual carefully, including the soldering instructions. It is critical especially in light of the fact that SMD capacitors do not have values printed on them. Thus, if you get them mixed up, you're in trouble. Stay organized and don't separate the parts from the bags they come in as you build. Put the unused caps back on or in the bag as you take them out of the "tape" they come in. In short- take your time, as the manual says.
With the right tools, soldering was pretty easy - as they provide good pad size for all but a couple of components (which were therefore a little tricky).
So how well does it work? I powered it up slowly with my variable voltage supply to avoid blowing things if something was wrong. Fortunately I had no difficulties. The current stayed low as I turned the supply up. A good sign. With that "smoke test" passed, I applied some signals, first from my audio sig-gen, and then from my IPOD. It worked exactly as advertised. Great volume/power, and the chip barely gets warm (I think there is a metal tab under it that sinks heat to the ground-plane on the board. Otherwise, even at 90% efficiency, a Watt or two would be dissipated and it would get toasty). Works well from about 8 volts to 18 volts. I tested mostly at 12v, but ran it up to 16V and at high volume was drawing around 0.8 Amps at peak points of the music. So that's about 12 Watts into the speaker. Very loud. I'm sure it will hit 20W at the 18V end of the spec, as advertised...
Haven't had a chance to look at audio distortion yet. The output waveform is hard to interpret on a scope, as the squarewave is dominant. A look at the radiated spectrum shows a 267 kHz fundamental and tons of harmonics out to about 30 MHz, and then quite clean after that (except for a blob around 76 MHz). So if you're not worried about using AM radios or ham radios and such in its vicinity, it seems to be a great amp...
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