Designing with O.A.C.'s

Polychlorinated Biphenyls (PCB) are a group of very stable chemicals which resist change from ageing and were widely used as dielectric fluid in capacitors.

https://www.chemsafetypro.com/Topics/Restriction/EU_RoHS_2_EU_RoHS_Directive.html
https://www.ncbi.nlm.nih.gov/books/NBK361696/

Unless I'm very wrong, every audio preamp and amplifier circuit uses metal can capacitors; and even if only in supply decoupling/smoothing, the signal still flows in them.

Whereas before certain characteristics of ageing would have been delayed for years, these characteristics now make themselves known audibly after the equipment has been in continuous operation for a matter of hours/days.

Such prior characteristics allowed slight design errors to go unnoticed (or unnoticed errors to remain unnoticed), especially with equipment which was only switched-on for a few hours at a time, when needed for listening. This would push out ageing for perhaps close to a human lifetime.

But now (since 2006 for European made equipment) for constantly on equipment such slight errors are laid bare within a matter of hours or days depending on the severity of the error.



Edited by Graham Slee - 25 Feb 2019 at 10:01am

No Ash, the point is I design for this worse case. The story is about what happened 13+ years ago. Eventually the circuitry was all scrapped. Everything since is all new, made to work without reliance on "audio grade" components - without polychlorinated biphenyls. I just like to raise the issue at times because it seems I'm unique and it only applied to me, except I'm not unique, or perhaps my hearing is, and in-fact it must be, because nobody else seems to have noticed.

I only ask because you once predicted the optimum working life of one of your products (Majestic?) if left powered up permanently to be a period of just over 11 years, if I recall correctly. It was merely a projected estimate but you acknowledge the physics that some electronic components can eventually deteriorate with age.