Favorite Practice/small group amp

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Attached is a schematic of my favorite DIY guitar "practice" amplifier. I call it the "Classy Lassy" because the enclosure is made from recycled lumber and the speakers harvested out of "junk" equipment.

The 5 Mohm input impedance doesn load my guitar (piezo or inductive pickups) and the amp also makes a portable radio sound GOOD! I did not want high power, but good sound quality for this amp, thus the LM386-4 based designs.

As noted on the schematic, my hat's off to Runoffgroove.com for their "Ruby" design.

Photos of completed amplifier to follow in another post.

(originally posted in "chip amps" but suggested to be posted here.)


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Classy Pic

Attached is a photo of the Classy Lassy.


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Classy Interior #3

Here is another shot of the interior bottom, showing the twin duplex recepticles I installed on the back panel.

I used a "closed and ported" box design for this, and it seems to work well.

I use a "hot glue" gun to tie down my wires where I want them to be tied.

I do have an issue of a slight amount of 120 Hz "buzz" when the the system volume is turned up with no signal in - but that could be rectified through some judicious cable shielding and routing.

For my use - as a "living room" style practice amp, I just don't worry about the small buzz - it is low enough that I only hear it when all is silent around me.

I hope you like it!



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Hi, I like it.
It is a true unique work of art. No redundant things like "nice" silk-screen-covered-PCB's, which would imply serial production. And honest woodwork.

Here's a picture of one of my projects, that did unfortunately not survive. It's intestines have never been photographed, what a shame. There was a 2xEL84 amp inside of which the power transformer went up in smoke. :bawling: After that the power amp was a TDA1519 from some car radio. Now the cabinet is standing in my garage for some future project. Here is a photo from the front side.



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Great Cab!

Definately a great cabinet - You did FINE work!!!

Suggestion for your cabinet -

You might look into some work with the 1875 chip - also, check out Canakit.net for some really well built 2003 based amp modules. Ive used a couple of them in some of my work, and copied the circuit used in others.

The advantage of the Canakit is the PC board - and these kits come with heatsinks for the chip amps.

Basic design suggestion - always plan for at least 1.5 to 2 times the power supply current capability than you think you'll need!
(All my amps are overdesigned - but that helps to make them "bulletproof").

If you check out ssguitar.com, in the Schematics section, you'll find several of my designs.

Good luck and good building!
Buzz solved!

I mentioned in a prior post that I had a slight buzz in the amplifier output - it was a ground loop - I had too many ground wires running. I removed one that was especially long and the buzz went away! Yippee!!

Lesson: Watch out for multiple ground paths in instillation - you can "shoot yourself in the foot".
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