Let's Build Something - Audio Amp

May 9, 2018 

Let's Build Something - Audio Amp

Pete Juliano N6QW co-authored a series of articles for "QRP Quarterly" over three years ago titled "Let's Build Something". The "something" was a beginners Home Brew SSB Transceiver for 40 Meters broken up into two main parts and further sub-divided by each stage.

Part I was a Direct Conversion Receiver and the first stage was a discrete component Audio Amplifier.  Pete's build method was a Manhattan style using W1REX MeSquares.

  

I converted the audio amplifier circuit to K7QO Chuck Adams' "Muppet" style PCB design. I use the free ExpressPCB software (run under WINE in Linux), to design, then print the top copper layer to a PDF.  Import the PDF into GIMP to "flip" the image.  The "flipped" image is then laser printed on glossy photo paper. Ready to do the toner transfer to bare (shiny & clean) copper clad pcb board. Which is then etched.

Sound like a lot of steps but it goes quick after you have the design.

 PCB DESIGN

"FLIPPED" IMAGE

COMPLETED PCB READY FOR SOLDER

K7QO Chuck, uses a thermal laminator to generate the heat and pressure to transfer the toner to the PCB material, He has it down to a science. I use a GE clothes iron than does the job as long as I leave a wide margin with no traces from the edge of the PCB.

The Mouser order is here with the SMD parts so I'll start melting solder in the next couple days. (Real Life has been interfering with bench time!)

73

AB1OP Ralph

Addendum:

LBS_AUDIO_AMP_partslist
part ID for AB1OP PCB diagram
================================
C1  10 NF
C2  100 NF
C3  100 NF
C4  150 PF
C5  10 UF ELECTROLYTIC (observe polarity)
C6  4.7 UF ELECTROLYTIC (observe polarity)
C7  470 UF ELECTROLYTIC (observe polarity)

R1  100K
R2  10K
R3  100 OHM
R4  1K
R5  470 OHM 1/2W
R6  10K POT
R7  100K
R8  10K
R9  10K
R10 1 OHM 1/2W
R11 1 OHM 1/2W
R12 1.3K

D1  1N4148 (observe polarity)
D2  1N4148 (observe polarity)

Q1  2N3904 NPN (observe orientation - flat right)
Q2  2N3904 NPN (observe orientation - flat right)
Q3  2N3904 NPN (observe orientation - flat right)

Q4  2N3906 PNP (observe orientation - flat left)