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.

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.

No. 5 speaks.

and what a lovely voice it is. even through a Crate speaker (i’m saving the better speakers for when the testing phase is over). overall, i’d say a success for cheap transformers, Radio Shack parts, and a few pieces taken from a busted computer power supply.

audio notes: it was late, and i was annoying enough playing at midnight. the mic is sitting just above the speaker which was laying face up in a milk crate. i’m currently using a 100k audio pot, and i think it would fair better with a 1M. overall though, the amp is surprisingly quiet at mid volume. i still need to drill out the hole for AC connector, but it will come in due time. for now, it’s making sound and that’s a huge first step for me.

5E3: Schematics and Ideas

5e3_schem
I’m hoping this will clear things up for the night. Practical matters have brought about the decision to build a tube amplifier. In this case, I’m going to get a WeberVST kit as not to go it solo on the first attempt. The winner of much debate as to which circuit to start with is the ever popular 5E3, a Fender ’57 Tweed Deluxe circuit.

Unfortunately, this circuit isn’t quite ideal. The goal for our prototype is going to be about balancing loudness with clarity and transforming its bluesy rock tone into something a little smoother and less aggressive. We’re going to attempt lowering the gain in the preamp by using tubes with a lower gain factor and increasing wattage in the output stage which will include substituting some 6L6 variety for the standard 6V6s. The use of two separate volume controls seems to be pointless for our purposes as well. I think I’ll probably wind up setting up a treble and bass tone stack by dumping one of the volume pots.

Anyone care to buy a Marshall 2×12 4102?

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.

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.