Ramsey 2013 Catalog - page 21

Audio Amps & Accessories
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First we designed the UAM2, the extremely popular audio amplifier module that provides 20 watts of clean audio with virtually no heat... or heatsink! People loved it, and “stuck”
them everywhere, from the back of speakers to inside their custom equipment to drive speakers. Last year saw the introduction of the “big
brother” of the UAM2, our UAM4. The UAM4 upped the ante; this little 2.5”
board provided 42 watts of stereo from a single SMT device!
Just like the UAM2, people fell in love with it, and then
they suggested we put together a complete audio ampli-
fier system based on the UAM4 design. Their requests
seemed like a great idea, so the UAM4SYS was born!
Our goal was to make a universal amplifier that is both com-
patible with anyone’s system requirements, and could be simply
plugged in and used. Sounds simple, but it took some serious
design work, and resulted in a lot of seriously awesome features!
Like the UAM4, the amplifier is based on a single SMT device that runs
in class D, which means it’s highly efficient (up to 87%) and produces
very little heat. It provides stereo audio power of 21 watts per channel, or
42 watts total audio power!
Easy-to-use board jumpers offer selectable gain of +22dB,
+25dB, +29.5dB or +36dB to match your input levels.
Board jumpers also enable protection and shutdown
options as well as stereo/mono/bridge mode. The amplifier
also features built-in click and pop suppression to protect not
only your ears and sanity, but your speakers and equipment!
Construction wise, the entire amplifier assembly is nicely designed
around a main board and a front panel control board. The micro-minia-
ture SMT amplifier and related SMT components are pre-installed on the
main board. The remaining parts are through-hole to make construction sim-
ple. Look at the front and rear view of the boards... what’s missing? Yep, no
heatsinks! The amplifier runs 87% efficient, and produces little (if any) heat!
The high impedance input is designed to use your choice of either a balanced line input or an unbalanced signal source.
A single stereo 3.5mm input can be used for a single stereo unbalanced input (i.e. a typical computer audio stereo cable)
and there are separate 3.5mm left and right audio inputs that can be used as balanced (TRS) or separate unbalanced
inputs. It’s your choice!
Speaker outputs are provided on the rear panel via spring clip terminal blocks compatible with 14-28AWG speaker wire. Separate left and right line outputs are also provided on the
rear panel via RCA unbalanced connectors. Best of all, you can select these outputs to be either pre or post processing!
Front panel controls are all DC or digital, giving you noise-free operation. No noisy/touchy volume pots ever again! Volume, bass, treble, and balance controls are provided to let you
configure the audio exactly to your personal preferences. In addition, mute and loudness on/off’s with matching LED indicators are provided on the front panel.
We’re especially proud of the headphone output circuit on the UAM4SYS. The standard 3.5mm stereo headphone jack on the front panel is controlled with digital up/down push but-
ton controls. This gives you 64 steps of audio level, and even stores your last setting so your headphone level will remain the same! The headphone jack is also pre-mute to allow
monitoring while the speakers are muted. It also makes it possible to have a “single master” unit with remote amplifiers daisy-chained or bridged together with the ability to turn one
off individually without disturbing the others downstream. That’s just one of the many systems you can implement with the UAM4SYS - the only limit is your creativity and imagina-
An over-temp LED is provided on the front panel to indicate problems like shorted outputs. The amplifier also detects this condition and automatically shuts down for protection until
the short is cleared. Considering all these features, you may be surprised to learn that we managed to fit the whole thing in a compact anodized aluminum case that is a mere 1.6”
high! It makes an attractive addition to any equipment stack or computer setting.
If you’re looking for a great way to properly drive speaker monitors from the line out of your computer, the UAM4SYS is perfect. One single stereo input cable between the computer
and the UAM4SYS, a pair of decent nearfield monitor speakers, and you’re all set. This is great for people that use their PC for audio and video editing. It’s also the perfect choice for
anyone looking for a high quality amplifier for an iPod or MP3 player.
Input power is 12-18VDC. At 18VDC and providing maximum power output, the high efficiency amplifier only draws 3.3A! The broad power input range also makes it perfect for
automobile use. Just plug it into an accessory power plug (formerly known as a cigarette lighter plug!). A lot of customers use their own power supplies or use the UAM4SYS in a
mobile environment, so we do not include a power supply. The optional SPS183 is a compact desktop switching power supply that provides 18VDC to produce the maxi-
mum output power of the amplifier. It has a wide input range of 100-240VAC so it’s compatible with domestic or international mains. (If you order the factory assembled
and tested version, we include the power supply so you can plug it in and crank it up!) The complete amplifier measures 5.6” x 6.6” x 1.6”. If you’ve been looking for the
perfect audio amplifier, look no further!
(My daughter’s primary system, the UAM4S, her iPod and iPhone, and several gigs of Pink Floyd cranking away!)
42 Watt Stereo Amplifier Kit
42 Watt Stereo Amplifier, Factory Assembled & Tested, With SPS183 Power Supply
18VDC, 3.3A Switching Power Supply, 100-240VAC, 50/60Hz
42 watt class D amplifier spread spectrum design!
Highly efficient heat-free operation!
Built-in click and pop suppression!
0.1% distortion!
Balanced and unbalanced audio inputs!
All DC digital controls for noise-free operation!
Selectable pre/post process line outputs!
Short circuit proof!
Operates on 12-18VDC at a mere 3.3A!
Compact and attractive shielded aluminum case!
The Ultimate High-Tech
Super Efficient Amplifier Solution!
42W Universal Stereo Amplifier System
Audio Output:
2 x 21W stereo mode, 8 ohms
1 x 42W mono mode, 4 ohms
91dB into 8 ohms, 22Hz-22kHz
Audio Input:
Balanced, unbalanced, hi-Z
Gain Adjust:
Jumper settings, +22dB,
+25dB, +29.5dB, +36dB
90dB at 1kHz
Up to 87%
Short circuit, thermal overload,
Auto short shutdown
Auto thermal shutdown
Modulation Scheme:
Spread-spectrum (SSM
Clock frequency 200kHz ±4kHz
Line Outputs:
Selectable pre/post processing,
dual RCA unbalanced
Headphone Out:
64 step digital level control with
memory, 3.5mm front panel
Speaker Out:
Spring clamp terminal block, 14-
28AWG, rear panel
Front Panel Controls:
Volume, bass, treble, balance, dig-
ital DC controls
Digital push button with LED
Digital push button with LED
On/off with LED
Over Temp:
LED indicator
Audio Input:
3.5mm stereo unbalanced
3.5mm balanced/unbalanced
each channel, 10K impedance
Anodized aluminum
Power Supply:
12VDC to 18VDC, 3.3A at 18VDC,
2.1mm center positive rear panel
5.28” x 6.2” x 1.2” board
5.6” x 6.6” x 1.6” case
1.24 lbs
Wired & Tested
iPod or Dark Side
of the Moon Files
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