Ramsey Electronics 2 1/2 Watt Super Sleuth Audio Amplifier, BN9 User Manual
Keep several of these for:
• Audio booster amps for radios, Walkmans
etc.
• Replacement amplifiers
• High sensitivity long distance listening
amplifier for ‘Big Ear super sleuth’ snooping!
• Mini PA systems
• Telephone amplifiers
• Intercom systems
• Anywhere some quick audio amplification to
speaker level is needed
The BN9 combines a high gain transistor pre-amp with the powerful LM-380 audio amplifier for over two
watts of audio. Your choice of either a gain of 50 or 3000! Runs on 8 to 15 volts, drives any speaker from
3 to 45 ohms with less than one percent distortion.
Kit No. BN9
INTRODUCTION TO THE BN9
The BN9 is a high gain miniature amplifier with all sorts of possible applications, limited only by your
imagination. Its small size and economical price make it a useful addition to many projects and repairs.
The BN9 has an amplification gain factor of 3000 with as much as 2 1/2 watts of audio power output.
It can also be configured for a gain of only 50 to make it versatile for any number of applications.
While high gain may be used for projects such as ‘super sleuthing, low gain can be used for Walkman boosting and telephone boosting.
This kit is called the super sleuth due to the very high gain it can be configured for. In this mode it
can be combined with a sensitive microphone and parabolic dish to pick up sounds from hundreds
of feet away such as:
• Listening to birds and wildlife from a distance.
• Keeping an ear on the kids in the back yard.
• Building up a nice hearing aid for folks who can’t afford or don’t need a commercial hearing
aid.
• To hear what is happening on the field at sporting events.
BN9 PARTS LIST
❒
2 .01µF ceramic disk capacitors (C1, C2)
❒ 3 4.7µF or 10µF electrolytic capacitors (C3,C4,C6)
❒ 1 100µF to 500µF electrolytic capacitor (C5)
❒ 1 220K ohm resistor (red-red-yellow) (R1)
❒ 1 10K ohm resistor (brown-black-orange) (R2)
❒ 1 NPN transistor, 2N3904 (Q1)
❒ 1 LM380 audio amplifier IC (U1)
Microphone
(not included)
+8 to 15VDc
gnd
speaker (not included)
BN9 PC BOARD ASSEMBLY
As you can see this is a fairly simple and straightforward project, but be careful! Don’t rush and
improperly mount a part or leave long lead lengths on components. As all good technicians and
experimenters know, parts must be mounted flush to the PC board. Not only for mechanical strength
and looks, but also to prevent oscillation problems by long lead lengths acting as small antennas.
Just follow the assembly instructions carefully and take your time. Before you know it you will be
satisfied with your working project!
ASSEMBLY OF THE BN9
❒ 1. Orient the circuit board as shown in the Parts Layout Diagram.
❒ 2. Install U1, the LM-380 IC into the PC board, making sure that all 14 pins are in their proper
holes. Also note in which direction the notch is oriented in the Parts Layout Diagram. Make sure
U1 is mounted in the same way when you solder it in. To make soldering easier, flip the board
over so the pins are facing up. This way the part can be soldered flush to the board with ease.
Don’t worry about all the pins being tied together in the center, these are grounding pins that also
act as heat sinks to keep your amp from getting too hot during use.
❒ 3. Install Q1, the 2N3904 transistor. Notice the correct position of it’s flat side. Guide all three
leads into their respective holes and solder the part in place.
❒ 4. Install R1, a 220K ohm resistor (red-red-yellow).
❒ 5. Install R2, a 10K ohm resistor (brown-black-orange).
❒ 6. Install C1, a .01µF ceramic disk capacitor (marked 10nF, 103 or .01).
❒ 7. Install C2, another .01µF ceramic disk capacitor (marked 10nF, 103 or .01).
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