Note: The circuit is from the front page of the data sheet. There are no tricks here. Also, I DO NOT have any PCBs available for sale. The layout is provided so that you can photoetch your own board. Your local electronics store (not Radio Shack) can help you with the supplies you'll need.

Amp Number One
Picture 1 (54k): The outside of the amp case. Not very interesting.The case is a radio shack model 270-274 and is 3^1/16 x 8^1/4 x 6^1/8. Not very big to stuff all that amp into, right?
Picture 2 (90K): This is a top view of the topless amp. I stole the transformer out of a Pioneer reciever that bit the dust and you can see the filter caps. The rectifier is mounted to the PC board that connects the filter caps. Sorry, but no pix of that detail.
Picture 3 (102k): This is a closeup of the modules. These are my two develpment versions and as such have only a little bit in common with the version on this page. Note the 10K PC mount pots in the signal path for trimming the input levels.
Picture 4 (65k): This is a left side view of the amp. Here you see the modules in profile, the filter caps end on, and you can glimpse the rectifier. It also gives you a good idea of how packed the case is.
Picture 5 (57k): This is a right side closeup of the output terminal area. You can see part of the transformer, the output wiring (dual runs of parallel 20ga zip cord). Also notice the lack of an output network DON'T DO THIS. The output network of the resistor and inductor is cheap insurance. This amp is a bad example electrically. Use the output network. It's so easy, why bother not to?
Picture 6 (55k): This is a rear view, giving a better look at the binding post outputs and showing the cheesey RCA jacks I used. FWIW, the outputs are the Radio Shack dual binding posts (274-718) and they're really not that bad. The bitch is that you have to drill two fairly precise 1/2" holes to mount each one. Not an easy task if you ask me. Keep that file handy.
More Pictures!
Amp Number Two
Picture 7 (50k): Three and a half of the four amp modules crammed into the new amp. The case is the same as the old one, with an identical transformer, bigger caps, and banana jacks instead of binding posts.
Picture 8 (48k): Closeup of said modules, reverse angle. Note the polished heatsink (1 degC/W better transfer!) and the liberal application of heatsink grease. That @*#^$ gets everywhere.
Picture 9 (95k): Up close and personal with modules 3 and 4, as well as a little bit of the trans and the output jacks. I omitted the output networks dure to extreme space constraints.
Picture 10 (27k): Overhead shot showing the topology of the amp. Nothing special here.
Picture 11 (52k): Closer overhead shot showing all four modules and the rectifier. Note the liberal application of electrical tabe between the rectifier PCB and the transformer...
Picture 12 (24k):The famed output jacks. Man they look bad....
Picture 13 (23k): Back angle of the output jacks and the transformer. You can see that I made this one a lot neater. The zip ties were $0.01 each, so I invested :-).

• (1) LM3886T or TF
• (2) 1K 5% carbon comp resistors
• (1) 20K 5% carbon comp resistor
• (1) 33K 5% carbon comp resistor
• (1) 100uF electrolytic cap, axial lead. 35WVDC should be fine.
• (1) 10uF decoupling cap of your choice, axial lead. (I used a nonpolar elec once, and a tantalum another time I recommend film caps for this)
• (1) 10 ohm 5 watt noninductive resistor (output network). I use wirewounds, but performance is slightly degraded. Not enough to worry about tho.
• (1) 0.7uH inductor (output network). Make this by winding about 15 turns of 18 guage magnet wire around the body of the afforementioned 10 ohm resistor and soldering to the resistor leads. It won't be 0.7uH, but it'll work just fine.
• Heatsink and compound. This is essential!
• Power supply: Output of 20-84VCT DC, with big filter caps.
• PC board stock, hardware, wire, misc.

My costs went as follows:

Part	Source	Cost
LM3886TF	Sample	Free! (~$5US)
Transformer	Salvaged from a Pioneer reciever	Free!
Filter Capacitors	Salvaged	$1US
Discreet parts (resistors, caps, rectifier)	Radio Shack	~$5US
Heatsinks	salvaged	Free!
Everything else	junk box	Free!

Dave Paton        |        dave@dpaton.net        |