In the ongoing quest to advance and develop, sometimes one gets the feeling that a change isn't as good as a rest in some instances. I took some faulty audio equipment to a local company who take on such repairs this week ahead of a couple of gigs with my band where we need reliable sound; obviously. One piece of kit is a rather old solid state bass guitar amplifier. It is a heavy old beast with a big chunk of steel plate inside for some mysterious reason lost in the smoky clouds of time's soldering iron.
The fault in this bass amp was intermittent but the repair guy could not replicate it in his workshop. He did point out that the original capacitors had been replaced with cheap components and that might explain why the whole thing hums even when all the controls are set to zero. Forget ever turning this beast up to "11". His diagnosis also explained why the fan would drop to half speed when the amp was cranked up, thus not cooling the circuitry as it should when the music hots up.
Anyway, all of that is by the by, my repair guy, the inimitable Geoff, told me a tale of the amplifier circuit it was, apparently, the first of its kind. A solid state amp designed in the 1990s at which you could throw almost anything signal-wise without it overheating, failing, or distorting. It would get so hot as to take the skin off a fingertip that inadvertently touched an exposed transistor casing, but would carry on working regardless. It seems that is not necessarily true for many of the devices we have today several decades later, which sometimes cut out and fail if you try and run them indoors never mind at that mythological "11". The secret Geoff told me was the beryllium arsenide field effect transistors, on the pioneering Hitachi board, if I understood him correctly.
Now, the sound of this amp when it is working perfectly is astounding, resilient, and as I mentioned before, copes with everything that a muso might throw at it. But, it is those elements in the transistor that threw me somewhat and make me worry ever so slightly. A queasy industry would presumably move away from arsenic compounds because of toxicity and disposal. Arsenic is as well-known a poison as old lace is an accoutrement for a good pre-war period crime drama as we all know. Nitrides might substitute, of course.
But, beryllium? It is perhaps not as well known a toxic element to the lay public as arsenic, but is nevertheless a nasty piece of work in its own right. There are an estimated 35 micrograms of the element in our bodies, assuming we are average. This is fine. But, beryllium has chemical characteristics akin to magnesium and can substitute for that vital element in enzymes that rely on magnesium causing them to go seriously awry, such as those involved in DNA synthesis. Moreover, the body has no mechanism to clear this element and so it simply accumulates. With high levels of exposure, such as through breathing in dust containing beryllium, one can contract berylliosis, an irreversible pulmonary disease. The disease might take several years to become symptomatic and can be lethal or at best severely debilitating.
My audio repair guy Geoff warned me not to take a hacksaw to those "beryllium arsenide" transistors. The most likely configuration is that the beryllium is present as an oxide layer rather than there being a specific arsenide compound, unless readers know different! Either way he suggested that the result of cutting open one of these devices would be at least as fierce as those experienced by an ex-spy and his daughter opening their front door in Salisbury. I have told my bass player not to do any serious DIY on the circuitry, just in case, but I have told him it is safe to crank it up to 11 for the funkier songs we perform.
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase. His popular science book Deceived Wisdom is now available.