I was prototyping a circuit last week, spending many hours sitting in front of the breadboard, consumed in the truly fiddly task of cutting and wire-stripping a lot of tiny wires, managed to get it all together and the first time I fired it up it and plugged it into an amplifier all I could hear was screaming.
Well, as in software sometimes the bugs are an easy fix, particularly if you RTFM. In this case it turned out not to be related to the filter I was building at all — it was the power supply. I’m using a TC1044S charge pump, a tiny bit of magic that converts a positive 9 volt power supply (as used in most guitar pedals) into a negative 9 volt supply:Well, the 1044 uses a 10kHz oscillator to do its magic and I was pretty certain I was hearing one of the harmonics of 10kHz. I tried disconnecting the power to the 1044 and the screaming stopped.
It turns out the engineers that designed this chip had thought that a fixed frequency might be a problem in certain applications, and by connecting the mysteriously named “Boost” pin 1 to V+ it increases the oscillator’s frequency to 45kHz, well beyond the range of human hearing, though apparently not past that of quite a lot of animals, such as the humble hedgehog (45kHz), the rabbit (49kHz), gerbil (60kHz), and bats (115kHz). So the 1044 could be a real irritant if say a hedgehog or a dolphin were the one designing guitar pedals.
Dolphins’ hearing extends all the way into their sonar range (150kHz) which I assume means their hearing is the same as their sonar. Given this is also the same as their vocal range it would seem they could potentially vocalise what they’re “seeing” via sonar, so that rather than saying to their buddy, “look out, here comes a shark!” they could yell out the sonar image of a shark. Dolphin music would be pretty incredible. Maybe it is.
I was a bit surprised to learn that the common house cat has a hearing range up to 77kHz. Mice up to 79kHz. Just what are cats and mice listening to up there? Makes you wonder.
hedgehog image courtesy Wikimedia Commons
Where does Barkhausen get its name?
At the same time as I formed Barkhausen (as a band) I was also planning to start producing guitar pedals and/or Eurorack synthesizer modules. This enterprise was to be called Barkhausen Effects.
I’ve given up the idea of making electronic products. It’s hard to imagine how I could have made it a profitable venture in New Zealand, where there are enormous input tariffs on imported goods and the dollar is weak against foreign currencies. The price of my products would not have been remotely competitive. I could have had them produced in China or somewhere where labour is cheap but ethically I couldn’t countenance that. And then there was the prospect of actually hand-building hundreds of objects, all that soldering and such. It would have taken up a huge amount of time and energy.
I enjoyed the journey but in the end I’d rather just make music.
The rest of this post (which was originally written in 2015) relates to Barkhausen Effects:
I was originally planning on calling this enterprise Vollgas Klang Effekte, which translates from the German as “full throttle sound effects”. It had that gruff (vulgar) Germanic ring to it, especially if you said it in a Heavy Metal-inflected sorta way. Despite it sounding good it was silly. That’s not a bad thing in itself, but I was looking for something that actually meant something to me. And I found it. More… Was ist das Barkhausen?
It’s not like me to start with something simple like a three transistor distortion box — the world does not need another one of those. So I’ve been reading books like Don Lancaster’s Active Filter Cookbook and Texas Instruments Op Amps for Everyone (both apparently kinda classics in the field), though I suspect that latter title is a bit enthusiastic. I’m learning a lot, which is fun.
I haven’t owned a breadboard since the 1980s. I’ve been collecting ideas, parts, schematics and data sheets for integrated circuits a few months ago I didn’t know even existed. Analog Multipliers and Operational Transconductance Amplifiers are strange and interesting beasts. More… The Hard Yards