Arduino: 1-Watt 2m Transmitter with RF Signal Generator abram, September 15, 2021October 19, 2021 Since I do a lot of RF projects, I wanted to see if I could make a 2m power amplifier using a minimal set of components. I have a number of BS170 MOSFET transistors that I’ve used for dozens of applications over the years from guitar pedal pre-amps to digital… Continue Reading
7MHz Transmitter with AVR Soft-keyer abram, March 3, 2019October 19, 2021 In my last post, I went over the design of a Colpitts crystal oscillator design that put out a moderately clean 7 MHz signal. In order to match the output impedance to 50 Ω, an NPN feedback pair (at least that’s what I’m calling it) was designed. While meeting the… Continue Reading
Basic Voltage-Controlled Amplifier abram, September 1, 2017September 1, 2017 I’ve been looking at the theoretical principles that govern the voltage-controlled amplifier (VCA) recently and came across some simple VCA designs that caught my attention. A common technique involves a JFET and an opamp to achieve VCA type operation by using the JFET as a voltage-controlled resistor somewhere in the… Continue Reading
The Cicada: a push-pull vacuum tube amplifier build abram, August 8, 2017October 12, 2017 Well, 2017 is more than half over now. This means I should probably post something to get at least one post in for this year. I’ve been meaning to do a write up about this project for a while, but time isn’t as freely available as I would like it… Continue Reading
Class AB amplifier test abram, September 12, 2014September 12, 2014 this was an attempt at designing a simple transformer-less class AB amplifier using two BJT power transistors. i setup the USB fan to protect against thermal runaway and cool off the transistors during operation. it took me looking over several schematics to realize that the the emitters of both the… Continue Reading
solid-state tremolo for tube amps… abram, May 19, 2013July 27, 2020 i’ve have a CBS-era Fender Bantam Bass in for repair that looks like a bowl of spaghetti inside the chassis. it’s a slew of yellow wire spread from one side to the other that resembles the web of a drunken spider. the amp has been modified to include a tremolo,… Continue Reading
no. 5 re-appropriation… abram, February 16, 2013 this is a re-appropriation of a Fender Frontman 15-B. it’s one 8″ speaker in a closed cabinet primarily designed as a really cheap bass amp to be included in starter packs. having gutted the amp a few years ago and replaced it with the contents from the No. 5 tube… Continue Reading
TDA2040-based amp schematic with EQ… abram, June 4, 2012 well here’s the first draft of the simplest medium powered solid state design i could muster. TL082 can easily be substituted with a TL072 which is probably better anyhow (i just have all these TL082s laying around). the power supply i’m using more like 14-15V. both ICs should easily be… Continue Reading
TDA2040 amp prototype… abram, May 24, 2012 prototype of a 20-watt TDA2040 based amplifier that i’ve been working on. running a 12-volt power supply and it’s surprisingly loud. Continue Reading
LM386-based “Esteli” demo by Alex Wilson abram, May 12, 2012 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… Continue Reading