ARRL HB CHP 28 FIG. 10 (92), CHP28 FIG.15 (88-91)
Description: This article was originally featured in April 1983 QST. This circuit provides an LM386 for the audio gain and samples the output and provides an adjustable AGC DC voltage for the receiver. Also uses MPF102 and 2N3906 transistors.
QST JAN'05 by N4GG
The circuits is a dual (stereo) audio band pass filter between 300 to 2700 hz. The circuits uses LM324, two LM386, and 78L05 ICs. Click here for additional information.
ARRL HB (92) CHP 28 FIG 13, (88-91) CHP28 FIG.18
Description: This circuit provides three independently adjustable audio inputs into a LM386 audio amplifier and one output to drive a set of headphones.
QST Jul 98
Description: This is a unity gain audio circuit that allows the separate balancing of the positive and negative peak clipping to control audio splatter. The circuit also contains a post low pass Chebyshev filter at 3Khz. The input audio level required is 100 millivolts but this can be adjusted with R5. The circuit uses two 8 pin 741 ICs. and two 1N4148.
PE May 98
Description: This is a 4-Watt per channel, two channel audio amplifier on a 3" x 5" pc board. The two channels can be bridged for 8 Watts output. The circuit is powered from 12 to 20 VDC and uses an LM2877 IC.
Description: This is a single input, six output
audio distribution box that the author developed for administrating
the code test and code practice. The circuit is powered from DC or a
12V AC wall transformer. The gain is unity and provides six outputs
without loading the input. A single emitter follower transistor stage
drives Radio Shack audio transformers on each of the outputs.
Description: This is an interface for your computer's sound card fordecoding RTTY, PSK31, SSTV, HELLSCHREIBER and other modes. The circuit uses two transistors, and has all the interface connectors mounted on the P C Board
Description: This circuit provides a constant level buffer/amplifier for the volume control to the audio output of the R139 receiver. Circuit uses LM324 and LM7805.
Description: The circuit uses two microphones in parallel and 180degrees out of phase to cancel the noise picked up by the second microphone. Circuit uses four 2N2222 transistors and a 78L09.
Description: This is the "belt pack" intercom board that is compatible with ClearCom, see www.rcrowley.com/comclone for details
Description: This is published on page 53 Hints & Kinks. Circuit uses LM324 and LM386.
Description: This is a two board equalizer with a boost/cut control for each audio band with 30 dB. Gain control. There are a set of 10 LEDs displaying the low and high audio band levels in 3 dB steps. The projects use TLC2272, TL082, (2) LM3915, 78L05 and 78L08. The boards are sold as a set only.
QEX Sep/Oct01 (Tech Notes)
Description: This is a Class D pulse width modulated audio amplifier using the TPA2000D2 IC with 2 watts of audio output power. This project uses all surface mounted parts.
DESCRIPTION: This circuit uses two MC1458, one LM386, one MAX295, 78L05, and 78L12.
Note: Maxim has obsoleted the Max295 IC's; Make sure you can get the IC's before ordering the board!
Description: This is the board shown in the National Semiconductor Application Notes for the LM4752 IC. The board is 4" by 5" and accepts the TA07B leaded package. The circuit consists of 8 capacitors, 2 fixed resistors, 2 variable resistors, and the LM4752. The circuit is a dual (stereo) audio amplifier with 11 watts per channel. Great audio amp for so few parts. See the app notes at www.national.com/pf/LM/LM4752.html.
The SSM2165 speech compressor circuit replaces the SSM2166 previously offered. SSM2165 circuit consist of the SSM2165 from the app notes with pre and post gain controls. The mini-kit includes (2) OP113 opamps, SSM2165, 78L05, L1, the p c board, schematic, parts locations, parts list, and app note. The OP113, SSM2165 and L1 are surface mount. The board is 1.5" by 3.1 and is a double sided board. SCHEMATIC AND PARTS LIST