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The Terrible Screaming Has Stopped

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:TC1044SWell, 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


The Hard Yards

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


You gotta start somewhere…

Akio plumb worn out after very seriously watching birds all morning

Starting a guitar effects company must rank up there with opening restaurants as one of the riskier of business ventures, well, before we head into the territory of loan sharks and bomb disposal (everything is relative). People often invent things to solve their own problems — in my case I’m looking to create sounds from a guitar for Barkhausen that can’t be created by existing pedals (yes, I am doing this out of a fundamental need).

I’ve got quite a number of design ideas, just figuring out how to focus on one of them is a challenge. My plan is to initially produce an initial build of twenty pedals of a first design sometime in the first half of 2016.

I’ll be blogging about the progress of my first pedal design over the coming months. I hope you’ll tune in.

— Murray

PS. the pink box (the featured image above with sixteen knobs) is a modified 4ms Sweptoner I built over the winter. I added a PT2399-based echo (the white knobs) into the mix. Successfully tackling such a difficult build was one of the reasons I thought about doing my own thing. I’ll cover building the Sweptoner in a future post…