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notes to self

a document of a plodding mind

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solid-state tremolo for tube amps…

Posted on May 19, 2013July 27, 2020 by abram

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, reverb, and an effects loop…

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the Triode: final build

Posted on May 2, 2013 by abram

final build of my take on the Mitsumin Valvecaster.

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electronics at work

Posted on May 2, 2013 by abram
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Ampeg Super Jet SJ-12T repair…

Posted on April 5, 2013August 24, 2016 by abram

I’ve seen a lot of the same complaints on various forums regarding these amps. Basically, the amp starts to get noisy and the occasional arcing can be heard through the speaker. The problem seems more exaggerated when using the tremolo circuit which is just a phase-shift LFO modulating the negative grid voltage. I’m not so…

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NOAA 19 APT copy…

Posted on March 6, 2013March 6, 2013 by abram

just a copy with a homebrew 2m ground plane antenna on the roof top with the FT-60. pretty surprising results considering the antenna isn’t even tuned for 137MHz.

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arduino temperature TV…

Posted on February 25, 2013 by abram

kind of a goofy experiment, but really useful. i’ve had a lot of LM335Zs laying around for a while. my christmas present this year was a new Arduino Mega 2560 board that i’ve hardly had a chance to do anything with. using the lovely Space Tinkerer’s blog and the good ol’ TVOut library, i turned…

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simple phase shift oscillator…

Posted on February 22, 2013February 22, 2013 by abram

a practice in designing an oscillator. this particular circuit employs a 2N2222A transistor on 6 volts. i used this Electronic-Tutorials.ws page to design the circuit. there were many reasons for this experiment, but the most immediate was to act as a simple CW practice oscillator. the final circuit looks something like the following.

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light bulb current limiter…

Posted on February 20, 2013 by abram

homemade light bulb current limiter. i’ll add more to this later.

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sqrt() reverb…

Posted on February 17, 2013February 17, 2013 by abram

this was the final build before it shipped out. circuit is a simple MOSFET (BS170) driver stage followed by two JFET (J201) recovery stages. i’ve included a sound sample of a similar reverb i built later without the second recovery stage and clipping diodes. it makes for a much more subtle reverb, but also tames…

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about

Abram Morphew is an electrical engineer, bedroom musician, composer, naturalist, and amateur scientist. I play music in the the binary marketing show. This blog is a catalog of stuff that I make or bits of information that I think could prove useful later on when memory fails me.

 

I currently hold an Extra Class Amateur Radio Operator license and transmit on the air as K2NXF.

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40m amp amplifier Arduino atmega328 atmel audio bash bjt breadboard circuit code cw delay digital effect effects electrical electronics homebrew lfo linux LM386 mellotronium music no. 5 opamp oscillator pcb pedal photos php pt2399 pwm radio rf schematic stereo stompbox synth tape TDA2040 tl072 TL082 tube

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