Tag Archives: LM386

LM386-based “Esteli” demo by Alex Wilson

an older video, but one i’ve been wanting to post for some time. this is Alex Wilson of Son Cats playing on one of the several cigar-box amps i’ve constructed. this one, in particular, had one of the best sounds during the more work-with-what-is-available days. i thought the video was a great demo of an application best suited for a small 1/2 watt amp. thanks, Alex.

Arduino: second verse, same as first… sort of

well, not really. feeble attempt and making some sort of microprocessor controlled tempo clock, but a good exercise in the ATMEGA328s finicky behavior. don’t ask me what that squeal is. i think it comes from the way the input was wired up (mistaking the second sleeve as a synonym for ground) coupled with the PWM stream not having a negative offset, but who knows. eventually, i’ll move off the tone() crutch and start working with more interesting DSP. it’ll be nice to start using some of the memory on the chip.

i will also post the schematic for the delay pedal once i’ve got the values i want in it. i won’t have any time nor tools to tear into it until next week though.

Arduino: Analog Aerials

Essentially the oBITerator program with aerials instead of actual input signal. Of course, we’ve got to mix in the newly constructed PT2399 pedal. A little work needs to happen in the common-collector preamp in the delay pedal. I’ll be recalculating those values soon as well as switching out a couple of the ceramic caps. They sounded good on the bread board initially, but I’d like to have a little less cutoff. Of course, no experiment would be complete without an LM386-based cigar box amplifier powering a Weber 12″ signature alnico.

The Esteli: an LM386N-based cigar box amp

The Esteli: Cigar Box instrument LM386N-based Amp from abram on Vimeo.

Here’s the latest in general purpose amplifiers made from reused parts. The enclosure is an old cigar box for which i have quite an affection as an enclosure. I really do love the sound of wood in both the recording process and amplifiers. In the video, you can really get an idea of how it treats the sound when i open the top.

As opposed to the LightBox, the Esteli has two knobs. The top is for volume and the bottom a 10k pot in the gain look between pins 1 and 8 on the IC. I’d probably recommend a 50k in this configuration, but it does make the amp really loud which i think is better for the instrument side of things. The gain of the amp then floats around 100-200 depending on where the gain is set. For more information, see the LM386 Datasheet.

Square-wave Oscillator Meets PT2399…

Square-wave Oscillator with PT2399… from abram on Vimeo.

Very short video of the waveform captured using Xoscpe of the PT2399 applied to the LM386 square-wave oscillator. Sorry for the bad focusing. I was in a rush. I just needed a visual capture for later analysis.

[audio:http://abrammorphew.com/notes/wp-content/uploads/2011/06/osc_delay.mp3|titles=i just broke the gameboy]

…and here’s a clip of the aforementioned wave from from around the same time.

LM386 Square-wave Oscillator

Here’s a small LM386-based square-wave oscillator built from the following schematic. I replaced the 30k resistor with a 50k Potentiometer from my stash of parts which then, of course, acts as a pitch controller. The following audio is some track recordings made in Ableton 8.0 with a little filter on one track and some reverb the air-raid siren sounding noise.

LightBox prototype

here’s a small battery-powered guitar amp that i’ve constructed from reused parts. the housing is a busted computer power supply (some of which is in the No. 5) as well. i’ve got several options for this little fellow in mind, but, for now, it’s a tiny amp with a mean distortion. lo-fi enthusiasts should contact me if you’d like one custom built.

LightBox Prototype: a battery-powered guitar amp w/ distortion from abram on Vimeo.

the final layout

final circuit layout with pre-printed PC board

She’s big and bulky, but you can’t ask for too much when you’re dealing with pre-printed PC boards. The 22k resistor in the gain path makes for extremely high output (in terms of headphones). The 100k stereo potentiometer on the output side should make the noise floor a lot lower unless the knob is cranked. That’s what I was going for here since the application of this device will be mainly for when other loud instruments are being played in the room. A short trip to the electronics store should yield three more of these guys. After that, it’s onto the chassis.

the first of four…


This was my first attempt at building the circuit on the PC board. Unfortunately, I think I’m going to have to get a different board since this one isn’t quite big enough with two opamps. Soldering it is also a bitch considering it’s tiny and my iron tip isn’t as small as it should be.

The 1/8″ plug is the output soon to have a pot attached to it for volume control. I’ve been thinking about attaching an light meter to each channel, but I still need to know what the dimensions of the chassis will be before I jump that far into it.

two ears. two channels.

stereo headphone amplifier circuit

Double the circuit for stereo. This is a breadboard representation of a single “channel.” Each channel will have its separate PCB with controls. This one lacks a volume pot, but the output was more than enough. 750mW after hooking up the gain path resulted in ripping the ear buds out of my ears in order to avoid total deafness. Sadly to say, I have about as much luck avoiding electrocution as I do cutting myself with knives. I’ll keep to the low voltages for a little while longer.