Just built the little gem amp!

[Joecool85]

What a keeper!  Pretty cool little thing.  I hooked it up to a .5watt radio speaker I found and liked it ok, but wasn't impressed with the volume.  So I hooked it up to a 10" 30w Fender speaker and it kills!  Not insanley loud, but definetly plenty for practice.  I think I might lower the output cap though, it seems a little bass heavy to me right now.

[Paul Marossy]

Yeah, it's a pretty cool circuit, huh? 

[Joecool85]

So cool!  My brother is going to be over later tonight and he is bringing some speakers we can test on it.  Should be fun.

[Peter Snowberg]

Be sure to try a Ruby too!

Welcome to 386 land!

Be sure to try JRC's high voltage (18V) version, the JRC386BD. Sweet little chip. Next try running it from a 6-pack of AA cells rather than a 9V. After that, try running from 18V. The LM386-4 is also capable of running at 18V. Don't try to run the 386-1 version that hard as it will promptly die.

[Joecool85]

Does running it on AAs make it better?   I ran my 386-1 in the little gem on a 12volt jump started battery pack thing, its great.

Whats so good about the ruby btw?

[Peter Snowberg]

The AA pack is much beefier than a standard 9V. Your supply is better still. 

I've never built a ruby, but I've made similar circuits. The difference is that the 386 has a very low input impedance. The Ruby adds a high impedance buffer to the front of the circuit. Give it a shot.

The high voltage versions of this chip have larger output transistors. Running a -1 part on 12v may over stress it, given enough time and power chords. Check the chip for heating and if it seems hot, try adapting a little heat sink to the top.

[Joecool85]

No heat issues at all.  I played it for half an hour running that 10" speaker on 12volts, no problem.  It says on the box (bought it at radioshack) that it can take up to 12 nominal, 15volt max.

It says at runoffgroove that to make it have less bass you can adjust the output cap, what do you guys recommend for running a 2.5" speaker?

[krister]

Hey Joecool,

I built the little gem too. I thought it was basss heavy too, so I added the buffer from the ruby on the front before the input cap and wahla no more tone sucking and your treble will be back. No need to change the input cap. It is an input impendance issue that is too low on the little gem, which the buffer fixes. I used an MPF102 JFET from Rat Shack. I love the little gem in this configuration, much better than the original schematic.

Kris

[Joecool85]

Do you just add the JFET or the resistors to ground and stuff? 

[krister]

I looked at the ruby schematic and added the 1M5 resistor, MPF102 and 3k9 resistor. Input to the gate, 1M5 resistor gate to ground, .01uF input cap to source, 3k9 resistor to ground, and drain to +9v, the rest was stock Little Gem. It works great!

Kris

[toneless]

LM386s are great chips! You can make good practise amps and fuzz-overdrive pedals with minimal parts. IMHO nothing wrong with the bass... use BIG caps!

[Peter Snowberg]

The thing that seems to amaze most people is to plug a 386 amp into a 4x12 cabinet. 

Wonderful little chips indeed!

[krister]

The bass is good. It was just bothering me that the highs weren't coming through like I wanted them to hence the buffer. I could tell the signal was being loaded down, same reason I didn't use my Cry Baby for years due to the loading effect when you turn it off. Then I learned how to fix it with a buffer from RG Keen's GeoFex site and I found out about some other cry baby mods that I did. I find it very liberating to be able go in and make changes to get the sounds I'm looking for.

Kris

PS Peter, I plug mine into a Marshall 2x12 with greenbacks and I turn it up all the way. It sounds awesome

[Joecool85]

I looked at the ruby schematic and added the 1M5 resistor, MPF102 and 3k9 resistor. Input to the gate, 1M5 resistor gate to ground, .01uF input cap to source, 3k9 resistor to ground, and drain to +9v, the rest was stock Little Gem. It works great!

Kris

You mean like this:

[Peter Snowberg]

That looks good to me.

One more addition.... Put a 10uF cap in series with the pot between pins 1 and 8. + side connects to pin 8.

You may also want to play with the 0.01uF value a little. Try a larger cap there.

[krister]

That is exactly what I did. It works perfectly. I didn't need to a 10uF cap between pins 1&8 the 5K gain pot only.

When I built Aron's smash drive I put some small resistors and a 10uF cap between pins 1&8 (I tried it with out and the chip ocillated like crazy, when I hard wired the pins) since I omitted the gain/drive pot and use the guitar's volume control instead, but the Smash Drive is used as a distortion effect and not an amp. It sounds great though, with the LM386N screaming.

Kris

[Joecool85]

These 386 chips are sweet :-)

I think I'm going to try that mod on my little gem a little later today and see what happens.