I'm building a Combo Amp for someone.

The cabinet is Pine 13" wide x 15" tall and 11" deep. All glued together and used a 1/2" roundover bit in my router for the edges.

The speaker is a vintage 10" Utah 15W 8ohm. The amp is my dual Im386 chip bridged amp design. Can run on 9volt battery or walwart and output is 1 to 2 watts.

Views: 2464

Replies to This Discussion


Amp is wired and the circuits are verified. Just need those dang tack strips for the grill cloth.The rat's nest.

Uhh  No. LOL

Took the amp for a test drive while waiting for the tack strips. It has a problem. Either I'm going to need to delete Volume 2 and convert Volume 1 to Master volume or I'm going to need to do something with the inputs.

Maybe so, I'll be going over it with a fine tooth comb next couple of days.

Hey Paul,

Been watching this amp build from the beginning with interest. Looks like you've made a variation of the Little Gem Mk II from runoffgroove.com with the gain pot mods instead of the fixed 10uF gain caps. Nice.

What I wondered, after looking at yours and the Little Gem MkII schematics, is the absence of a capacitor for the speaker, like seen in a single LM386 circuit.

Another difference is the LG schematic replacing the 10K volume pot for a 0.22uF cap leading into the 3 and 2 pins of the twin LM386.

Curious though, what issues are you having with the amp?

I based this on the Ruby amp and the Tufnel distortion pedal from Beavis Audio.

Just getting hum through the output speaker. Thought that some solder may have dripped into the volume pots when I was soldering everything together, but they are okay. I think the problem may be in the input circuit(since the changes from the first amp build are twin volumes and twin inputs), that's what I'm checking next anyway.

Both the Ruby and the Tufnel have a capacitor set in line with the output/speaker+ line from pin 5. That cap isolates the dc current inside the circuit, and allows the ac guitar signal to pass to the speaker.

(Not referring to the cap and resistor off of pin 5 to ground shown on the Ruby and Tufnel diagrams).

I may be mistaken, but without the capacitor mentioned, it's possible you have ac and dc power going to the speaker.

I used the output circuits from this:If caps are needed before the speaker, I'll have to use 2 right? 1 for each side of the output since this is a bridged amp?

Interesting. I think I'm going to have to make one up as shown in that schematic to see for myself.

The LM386N-4 IC chip, based on Texas Instruments data, at 16v battery/wall wart power, can put out 700mW (0.7 watts). But it can handle a max. of 18 volts, with a 1 watt output. So by bridging two as in the diagram, at max power, it can produce 2 watts output.

And a wallwart is optimum, since this circuit would drain batteries like a hungry vampire.

I use a 9volt walwart rated at 800ma

I'm using the Im386N1 chips, but you can switch them for the N4's.

Thought about adding caps between the output pins and the speaker to experiment with, but never got to it. A couple of Bi-Polar film caps maybe?


The Essential Pages

New to Cigar Box Nation? How to Play Cigar Box GuitarsFree Plans & How to Build Cigar Box GuitarsCigar Box Guitar Building Basics

Site Sponsor

Recommended Links & Resources

Discussion Forum

Tribute amps I've built

Started by Tom Hoglund Nov 7, 2022. 0 Replies

LM386 Amp w/ Switchable Clean Channel

Started by BrianQ.. Last reply by BrianQ. May 28, 2021. 1 Reply

Simple 1st Timer CBG Amp

Started by BrianQ.. Last reply by BrianQ. Sep 27, 2020. 25 Replies

Matching Speakers to LM386

Started by Southern Ray. Last reply by Southern Ray Aug 6, 2020. 11 Replies

Suggestions wanted for easy amp build

Started by Southern Ray. Last reply by Southern Ray Jun 15, 2020. 11 Replies

Ruby Amp

Started by BrianQ.. Last reply by Southern Ray May 16, 2020. 27 Replies

Low-Z pickup and components values

Started by Southern Ray. Last reply by Southern Ray May 13, 2020. 6 Replies


Started by Southern Ray. Last reply by Southern Ray May 2, 2020. 12 Replies

DIY Spring Reverb

Started by Kevin Keating. Last reply by Paul Craig Oct 17, 2019. 4 Replies

TDA2030A Amp

Started by Bama Hound. Last reply by Gary Stenzel Jul 23, 2017. 14 Replies

Home Brew Champ Tube Amp

Started by Scott aka Farmer Ted. Last reply by Paul Craig Feb 6, 2017. 3 Replies

Dual IM386 Chip amp

Started by Paul Craig. Last reply by Paul Craig Jan 26, 2017. 29 Replies

5 Watt Amp Kit (DIY Case)

Started by Walter Haapapuro. Last reply by Gene Jones Dec 7, 2016. 46 Replies

DIY reverb behold - I found this online

Started by Danny B.. Last reply by Paul Craig Nov 2, 2016. 3 Replies

Bass Cabinet project

Started by Murdoc_420. Last reply by Murdoc_420 Jul 15, 2016. 34 Replies

Kalamazoo Model 1 Deluxe

Started by Scott aka Farmer Ted. Last reply by Rick Alexander Jun 20, 2016. 12 Replies

LM386 amp and other stuff

Started by Denis U. Last reply by Denis U May 29, 2016. 19 Replies

Blog Posts

A Tribute

Posted by Ghostbuttons on January 15, 2023 at 12:00pm 1 Comment

Let’s talk Aeolian…

Posted by BrianQ. on August 26, 2022 at 5:05pm 0 Comments



© 2023   Created by Ben "C. B. Gitty" Baker.   Powered by

Badges  |  Report an Issue  |  Terms of Service

\uastyle>\ud/** Scrollup **/\ud.scrollup {\ud background: url("https://storage.ning.com/topology/rest/1.0/file/get/963882636?profile=original") no-repeat scroll 0 0 transparent;\ud bottom: 25px;\ud display: inline !important;\ud height: 40px;\ud opacity: 0.3 !important;\ud position: fixed;\ud right: 30px;\ud text-indent: -9999px;\ud width: 40px;\ud z-index: 999;\ud}\ud.scrollup:hover {\ud opacity:0.99!important;\ud}\ud \uascript type="text/javascript">\ud x$(document).ready(function(){\ud x$(window).scroll(function(){\ud if (x$(this).scrollTop() > 100) {\ud x$('.scrollup').fadeIn();\ud } else {\ud x$('.scrollup').fadeOut();\ud }\ud });\ud x$('.scrollup').click(function(){\ud x$("html, body").animate({ scrollTop: 0 }, 600);\ud return false;\ud });\ud });\ud \ua!-- End Scroll Up -->