Pages: [1]   Go Down
Author Topic: LM386 Guitar amp  (Read 2966 times)
0 Members and 1 Guest are viewing this topic.
Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi

I need someone to check if my breadboard layout of the amp is correct and if it could be done differently/better.

I want to control the Gain and Volume via pots, add a led to see when it's ON or OFF and perhaps an on/off switch or wiring so that the amp turns on when a cable is inserted to the line in jack.

The pot 10K

The yellow capacitors represent 0,47nF

The transistor is a 2N5457
Logged

Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Here's how I put it on the breadboard


* Skärmavbild 2012-05-14 kl. 09.33.08.png (92.71 KB, 851x873 - viewed 163 times.)
Logged

Dubai, UAE
Offline Offline
Edison Member
*
Karma: 21
Posts: 1670
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi,
   Can't confirm your circuit, I have only used to minimal circuit (least components version) from the datasheet, but what a great little chip, I am using one as the output of an Audino and it even makes an ok ipod docking station if you connect it to a PC Speaker.

Duane B

rcarduino.blogspot.com
Logged


Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey!

Okey  smiley . Could you post a pic of how you wired it or a breadboard view? I use Fritzing, really easy app for making breadboard pics!

The annoying thing is I can't find where I saw this layout at first!
Everywhere I look people seem to use different value capacitors and resistors, so I guess it doesn't matter that much, but probably there within a certain range of value.

If someone could post a breadboard layout or a drawing, whatever just not a schematic, I would be soooo happy!

The main problem is that ¨they¨ use a 25Ω rheostat which is more or less impossible to get. This is what i want to somehow come around :p...
Logged

Topsham, Vermont USA
Offline Offline
Edison Member
*
Karma: 23
Posts: 1753
... in The Woods In Vermont
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi,

25 ohms is an unusual low value for a pot: Where did they show this in the circuit?? Maybe that's not the real value??

I have used the LM386 a few times and it's easy to use and cheap. I include it in my Popular IC Assortment, which you can see here, with the datasheets etc: http://arduino-info.wikispaces.com/Popular-ICs

DISCLAIMER: Mention..ING stuff from my own shop... where LM386's are 5 for 75 cents .. http://goo.gl/xT4IG

At 15 cents it's no tragedy if you blow one up  smiley
Logged

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

Chester, UK
Offline Offline
Newbie
*
Karma: 0
Posts: 19
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
I need someone to check if my breadboard layout of the amp is correct and if it could be done differently/better.

From what I can see on your breadboard layout, LM386 pin 5 (output) and pin 6 (Vs) don't appear to be connected anywhere.

Also, the output coupling capacitor should be connected from output to load rather than from load to ground - and as it's an electrolytic, its +ve, in this case, must be on the output.
Logged

“Everything should be made as simple as possible, but no simpler.”

CO, USA
Offline Offline
God Member
*****
Karma: 4
Posts: 710
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

The annoying thing is I can't find where I saw this layout at first!
Everywhere I look people seem to use different value capacitors and resistors, so I guess it doesn't matter that much, but probably there within a certain range of value.

If someone could post a breadboard layout or a drawing, whatever just not a schematic, I would be soooo happy!

The main problem is that ¨they¨ use a 25Ω rheostat which is more or less impossible to get. This is what i want to somehow come around :p...

The 25 ohm rheostat is what's found in the Little Gem. Of course, you don't need an actual rheostat; you can use a pot. So whatever layout you're referring too, sounds as if someone just added that transistor as an output stage (or not, hard to tell the intent here, maybe it's supposed to be an input buffer, as in the Ruby, but then it wouldn't be connected directly to the speaker).

I don't use Fritzing, but if I were breadboarding this, I'd start by putting the +9V and GND leads from the battery into the power rails on the breadboard. I think that will simplify your layout.

The decoupling capacitor isn't hugely critical. The caps on the output will affect the tone, as they comprise a frequency dependent filter.

Looking at the LM386 pinout, it appears you don't have pin 5 (output) connected to anything. Your picture shows the indicator divot on the left, over by the "L", so that puts pin 5 above and right from the "6". And, as the pins on the transistor aren't labeled, it's hard to say whether those are correctly connected either. The pinout on that is GSD, but your fritzing drawing doesn't show which direction it's oriented.

I'm just guessing here, based on some small exposure to the LM386. Really would be good to see a schematic of the circuit you're trying to reproduce. 4 lines going to 'volume and gain control' aren't really helpful, because they don't show what's in that yellow box, and how those wires are connected to that.
« Last Edit: May 15, 2012, 08:03:25 pm by justjed » Logged

... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I realized now that a breadboard picture really doesn't help anyone here smiley-razz...

Here's the original schematic I found somewhere, I'll add ¨my version¨ too, I think it should be the same, but with a simpler IC symbol or what it's called.


Where I live we don't use cents and dollars smiley-wink , still the LM386 doesn't cost much as you say, hehe smiley-grin


* GuitarAmp.gif (13.2 KB, 306x303 - viewed 42 times.)

* Skärmavbild 2012-05-14 kl. 21.01.04.png (39.4 KB, 1088x786 - viewed 36 times.)
Logged

Dubai, UAE
Offline Offline
Edison Member
*
Karma: 21
Posts: 1670
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Hi,

In my Audino I have two switches which can be used to switch between two output capacitors it gives a similar effect on the tone as switching between a pickup at the bridge and a pickup at the neck of a guitar.

Larger values give a tone with more bass, smaller gives less bass.

DUane B
Logged


Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hey everyone that has posted on my topic!

I just wanted to announce that I got the amp working now this morning!  smiley-lol smiley-lol smiley-lol

Feels awesome to have built a cool little amp by my self for the first time! smiley

Loads of thanks to everyone!

I took the wise advise from justjed and hooked up 9V & Gnd to the side rails of my breadboard, made it a whole lot easier!


I'll upload a photo of my layout later!

I put a pot which now sits between the input and pin 3. This seems to control the volume and not the gain as I thought it would. At least the volume problem is solved :p


Can I put a pot between the cap and pin 1 , 8 ? Since thats where the gain is controlled it says on the data sheet.



Thanks again!

Peace out 4 now
Logged

CO, USA
Offline Offline
God Member
*****
Karma: 4
Posts: 710
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Glad you got it working. I'm quite curious as to the final schematic. I fixed the b0rken links in my post above.
Logged

... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Disaster!

Mysteriously my amp didn't work yesterday when I was just about to take it apart from the breadboard and solder it permanently!?
I have no idea why?

Now it only amplifies in a very small range on the pot.

Iv'e tried 2 different pots, so they aren't broken in some way...

I'll post how I wired everything as when it worked.


Please help! smiley-razz
Logged

Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

A Breadboard view.



* Skärmavbild 2012-05-17 kl. 13.04.56.png (115.8 KB, 1081x620 - viewed 77 times.)
Logged

CO, USA
Offline Offline
God Member
*****
Karma: 4
Posts: 710
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

A Breadboard view.

Assuming that is supposed to be like the schematic, then I don't see anything obvious -- but that's assuming you're on a solderless breadboard, and not perfboard as shown in that picture.

Diagnosing this is out of my depth, so I can suggest only that perhaps you've overdriven the LM386 and damaged it, or that you have a loose connection someplace.

If that drawing is really representative of your circuit, then you have nothing connected to pins 2, 4, and 5.
Logged

... it is poor civic hygiene to install technologies that could someday
facilitate a police state. -- Bruce Schneier

Sweden
Offline Offline
Newbie
*
Karma: 0
Posts: 25
Extremely rookie
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

I got it working again late last night. But now it sounds like a machine gun if i connect the potentiometer to the mono jack.

So I solved this by putting a 500K pot + 1KΩ resistor at the line out (pin 5), also added an extra capacitor between pins 1-8 with a switch so that the gain is activated when i want to. The pot worked fine as a volume control.

The weird thing is that I should be able to use a 10K pot according to every schematic Iv'e read smiley-razz?

Anyway It works now, but I'll solder it so that parts can be added easily just in case. 
Logged

Pages: [1]   Go Up
Jump to: