Yearly Archives: 2013

Using encoders with Arduino

I’ve been looking at using an encoder as a front panel control. Encoders are industry standard devices made by ALPS, Panasonic, Bourns and CTS among others. They come with and without a push-button switch and (not-counting the switch) have three terminals, labelled A, B and C. We can connect the C terminal to +Vcc or… Read More »

H-bridge motorised volume control

I came across Ian Johnston’s project to modify a Pioneer surround amp to incorporate a motorised volume control and decided to use his design as the basis for a small project. For his part, Ian hacked his design from parts he had available, whereas my design is fully realised and value engineered.  My main goal… Read More »

Designing with op-amps and single supplies

I thought I would make myself a crib sheet for the basics of designing with op amps. Then I thought I may as well post it here so I won’t have to remember where I put my crib sheet. This will be an ongoing thing. The subject is: Analogue audio design using op-amps with single-ended… Read More »

True Bypass Relay with Muting

Update – extra schematics and timing diagrams added (see below). Also TLP222G optofets are available in the shop here. There has been discussion on Stompville here (in the comment section) and on diystompboxes.com about problems with audio clicks when using a relay for true bypass. The consensus seems to be that the answer is to use… Read More »

P48 Phantom power from 9V d.c.

Here are a couple of options for generating proper 48V phantom power from a 9V supply. Before we get stuck into the details I should point out that the quiescent current for the first option is about 27mA and for the second about 52mA, so don’t be thinking you can run this from a PP3/1604/6LR61… Read More »