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
Differential Amplifier w/ Cathode Follower abram, August 22, 2016August 22, 2016 This is a circuit designed for a classroom project whereby the instructions were to “improve” a differential amplifier circuit. The differential amplifier design is essentially an exercise in understanding the inner workings of an opamp, and it effectively works in the same way. The figure below is a schematic for… Continue Reading
LightBox prototype abram, November 3, 2010November 3, 2010 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… Continue Reading
the final layout abram, June 22, 2009August 31, 2017 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… Continue Reading
the first of four… abram, June 18, 2009June 22, 2009 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… Continue Reading