Friend of mine had some LM380's, and I've been playing around with them. They are just as simple, and as low parts count as the LM386, but more power. And they accept the guitar with no problem. The data sheet I have says it's capable of 4 Watts. So it works as a preamp, and would also work as a small practice amp.There's a very noticable difference in power of the 386 and 380. I've just built one, and it really sounds good thru an 8" speaker. (in the tiny practice amp category of course)

My friend was a lucky dog - caught a Radio Shack moving to new location, and they sold their inventory to keep from moving it. He don't want to sell any of it, but he did give me a few pieces.

Yes Purpletheo, that's a good circuit, and the tlo71 is a good sounding chip. I think you will hear a defining difference between it and the old LM741. Using the LM386 as the driver, I used the double tlo72 as the reciever for my spring reverb unit.

The .1, also numbered as a 104, bypass cap goes on the power lines as close the chip as you can get it. I usually run my +/- power lines on the back side of the circuit board (underneath, the chip). Or, if you're handy with the soldering iron, you can solder the little .1 ceramic cap also on the backside of the chip from + power pin to the - ground pin.

The little preamp boxes I built for some friends, don't even have a circuit board. The bypass cap is soldered on the backside of the chip,the output cap soldered directly onto pin 5, and with a small piece of solid wire, I soldered the input pin directly onto the 1/4" input jack.

Also, I use the 3 pin 1/4" jacks, wire the 9V battery to the 3rd pin, so when they plug in, it powers up. That eliminates the need for a switch. Most of your stomp boxes are wired this way.

Sorry Joecool, I skipped over your post.
YES, the circuit you got drawed out is the one I use.

YES-stompin_T   "The Smokey" is the circuit I've been using. To get a little more bass response, I use a 220uc cap on the output. You can tailor this to suit your needs. The single coil pickups in my Strat needed a little more bass.

RE: Fuse
Sorry about that, I stateted that wrong. The wal-wart is wired in before the fuse, so it is fused with the rest of the amp.

Trying to send the 386 schematic, but I'm having trouble with my scanner. Always something to make one's day. Anyway, there's really nothing to it. Where the -/+ wires come in, I use a .1 ceramic bypass cap, as close to the chip as possible. I come straight in to the input - no input cap. I wire pins 2 and 4 together and hook to ground. I use a 220uf cap on the output, and that's it. On this particular circuit, I don't use pins 1,7, or 8, so I just clip them off and get them out of the way.

All the other 386 circuits you see, have so many parts, some may laugh at this one, but as previously posted, I play 3 times a week, and had this circuit in my 30W Kustom for quite some time now. If there were going to be any problems, they would have showed up by now. Also, friends using this circuit, have had no problems.

There might be applications, or guitar amps, where it might not work, or where you would need an input cap, or maybe a zobel network on the output, but so far, I've not had any problems.

Also, I'll say this again: If the amp input is sortered onto a circuit board, I would recommend just mounting the chip in a small box with 9V battery and use as you would any other effects box. Anyone reading this that didn't have the experience, could damage their amp circuit board, or maybe cause smoke !!

If I can get this scanner going, I'll send the drawing.

No problem joecool85. I'll get a shematic drawed up and posted asap.

The ones I built for some friends, as plug-in modules, are being used as guitar and mic preamps. One plugged into a PA system for a mic, and a couple into a powered mixer. So I don't think there would be any danger in this circuit causing any damage, as they have been using them for several months now with no complaints, just compliments.

I disconnected the input jack from the amp, wired the little 386 circuit to the jack, then wired the 386 into the amp where the input jack was. In other words, I put the 386 between the input jack, and the amp. (not good at explaining things) However, this could be a problem on certain amps if the input jack was mounted onto a circuit board, and shouldn't be attempted by any newbies. I play 3 times a week at church and wanted to cut down on the number of pieces I have to carry, and with the power supply mounted within the amp, no more battery purchases.

The simplest, would be as I did before, mount it in a little box and plug into it. The circuit is so small, it could even be mounted inside a guitar if there was room for a 9v battery. But again, that wouldn't be a job for a newbie probably.

As previously posted, only 2 parts to my circuit, a bypass cap between pins 6 and 4 (pins 4 & 2 are hooked together), and an output cap. The circuit is the size of a postage stamp. In this circuit, I do not use pins 1, 8, and 7, so I just snip them off with fingernail clips and get them out of the way.

The size of the output cap can be adjusted to suit your needs. I normally use a 220uf. The larger you go, the more bass response you get.

And YES, being able to use it as a power amp or preamp, makes this little chip amazing. When at all possible, I use it, to avoid high parts count of other chips.

The LM 386 I installed in my 30W Kustom, has only 2 parts - a .1 ceramic bypass cap, and a 220 uf output cap. I installed it right at the 1/4 input jack of the amp. To avoid messing with anything else within the amp, I had room in the case for a 9V DC wall wart, and 2 1000uf smoothing caps. I wired the wall wart to the AC where it comes in to the case just after the fuse. A very easy project, and added much needed extra SPL to this little 30W. I like it loud. I always run this amp volume on 7. Now I run it on 2.

Narrow minded, I accidently left out the input cap on one of my 386 preamps. But it worked great, so I quit using them. Depending on the project, a volume control can be used if needed.

This 30W Kustom is a chip amp. There's a possibility it could work differently for different amps - tube, transistor, etc. However, I've been building them in a small Radio Shack project box for family and friends as a plug-in preamp for guitars and mics. No complaints yet.

LM386 is a great little chip. I've been using it for a couple years.

I've been using the LM386 for couple years - before I saw the Ruby circuit. I installed the simple 386 circuit, without an input cap, just on the inside of my 30W Kustom guitar amp, working as a preamp. Works great. Added a lot of SPL to this amp. I was running the amp volume on 7. Now I run it on 2. Big difference for this little amp.

Yes, tight budget encourages inginuity. Some of these old computer speaker cables have 2 wires + a shield. Especially in opamp circuits, I'll use the 2 wires for +/-, then ground one end of the shield. Some cables have foil for shielding, and some stranded wire. I've cleared up quite a few hums with this method.

Great article on grounding. Everyone, at some time, have had grounding problems.

Also in the grounding / hum department is the word interference. I lived with various interference hums until I discovered shielded wire. I now use shielded wire for my inputs/outputs. Clip one end of the shield off, and run the other end to the star ground. This has really cleaned up a lot of my work. Also, on a budget, I keep an eye out at the flea mkts. for old computer speakers, usually for a couple bucks. Most of these have shielded wire. Some of the wire is too small for larger amps, but work very well for opamp/preamp circuits.

Hey guys - great site - gonna be good forum - my 1st post.
For the simple reason that I joy in junk, and have a couple good repair shop sources, I deal mainly in transistors. I have tried for years to build a simple guitar amp., but simplicity is almost impossible. They require so many stages, especially when you include a reverb section. I've seen commercial amps with as many as 11 stages. However, while attempting to repair an old 70s Peavey amp for a friend, I ordered the schematics. These schemayics turned out to be the answer to a lot of my problems - simplicity. In these schematics there's a simple preamp, gain stage, distortion, reverb driver/reciever, and all the tone, vol., eq. etc/ circuits. All of these are 1 to 3 transistor circuits. I've recently built all these circuits individually with common 3904/3906 transistors, and they work great.
Also, I just recently run across an actual "simple" reverb circuit by Forest Cook. It consist of 3 - one transistor preamps, and one LM386 for the driver.
I'm hoping to finally get my guitar amp on the road to completion with 3 stages: Preamp, a gain stage, and power amp, plus the reverb circuit of course.
Maybe I can learn something here, and try a chip amp next ??
Happy soldering and keep the good info coming.
Willy