Yearly Archives: 2015

Wien Bridge Oscillator

You may have gathered from my last-but-one post on bit-banging the AD9833 DDS module that I have been playing with audio oscillator designs. As part of this process, I have tried a few Wien bridge oscillator designs that purport to not require a proper non-linear device (such as a miniature lamp or an RA53 thermistor).… Read More »

Substituting the 2N5457

Since Fairchild finally discontinued the 2N5457 JFET along with a number of other JFETS in the TO92 package, prices have been rising and tales of fakes have been increasing on audio and stomp-box forums. You can still buy the 2N5457 from Central Semiconductor, but they are very expensive – too expensive for Stompville to consider… Read More »

Passive Dummy Load Project

Following on from my previous blogs about Connecting Loudspeakers to Amplifiers and Passive Dummy Loads for Amplifiers here is a project for a modest passive dummy load with a twist – I have included a differential ‘scope probe to facilitate monitoring of the signal on an oscilloscope. I managed to score a new-old-stock Grayhill switch… 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 »

True Bypass Relay SMD

We don’t do much SMD (surface mounted) work here at Stompville. When it comes to the True Bypass Relay however, smaller may just be better, so we designed and built a surface-mount version to see how small we can realistically make it – and the answer is about 30% smaller. That is 30% smaller on… Read More »

JFET Idss Matching

Idss for the 2SK596s JFET – as introduced in my previous blog – is an order of magnitude lower than (say) a 2N5457, so I have been revisiting the design of my Arduino-based automatic JFET matcher to be sure that I can use it to characterise the 2SK596s with good resolution. Along the way, I… Read More »