Category Archives: How To

Balanced piezo transducers

I was asked to comment on whether the Phantom Piezo Preamp (available in the shop here) is suitable for connecting to a balanced piezo transducer as covered by Chrisitan Liljedahl here. The short answers is yes, absolutely – the Phantom Piezo Preamp has balanced input and output and effectively you connect a single or double… Read More »

Protecting piezo preamps

I had an enquiry (which which puzzled me slightly) about using LED’s to protect the input of the Phantom Piezo Preamp (available to buy in the shop here). However it was noted that if a piezo transducer is dropped onto a hard surface, the voltage spike generated could be high enough to damage downstream electronics.… Read More »

Passive Dummy Loads for Amplifiers

Following on from my previous article on matching amplifiers and loudspeakers, this article offers some ideas for making passive dummy loads. Active dummy loads are fine, but if you need to test an expensive amplifier at full load, you do need to be pretty confident that you are connecting a load which is going to… Read More »

Connecting Loudspeakers to Amplifiers

Some amplifiers will be very unhappy if you max them out without an appropriate load – and inappropriate could mean open-circuit, short-circuit or just too high or too low. This article covers the basics of connecting loudspeakers to amplifiers – in this case I am thinking of solid-state guitar amplifiers which are generally going to… Read More »

Low-battery monitor with TC54 voltage detector

Update: Adding an output transistor – see below. So you’d kind of like to know when the battery in your stompbox  is getting a bit flat but you’re not sure how to proceed. The first problem is that you don’t want your low-battery monitoring circuit to make a significant contribution to battery drain – which… Read More »

Testing and Matching JFETS

Update: Matching JFETs – Revisited here. Update: Kits available in the shop here. Update: Matched sets of JFETs available for sale here. We’re talking here about N-channel depletion-mode junction field-effect transistors. “Field effect” because the current flowing between source and drain is controlled by the electric field strength at the gate.  Impedance at the gate… Read More »

How to tin a PCB without using expensive tinning solution

I learned this technique a good few years ago from an old boy who was a prototype wireman for a large electronics company.  I’ve never seen it mentioned on t’Internet so I thought I would write it up as a how-to. You will need the following: Your circuit board – after etching and before drilling*… Read More »