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Old 13th Oct 2017, 7:57 pm   #146
kalee20
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Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
Default Re: Audiophoolery. 'Cable Break In' - I never knew that!

Quote:
Originally Posted by GrimJosef View Post
I'll bet the seals in valve bases were optimised for, say a range of 0C to 150C or so. Military spec valves might be rated to work from lower temps (high-altitude aircraft) to higher (badly ventilated kit inside hot parts of tanks or ships). But surely they weren't designed to go down to genuine cryo temperatures.
I'd be rather dubious about subjecting a valve, with its vulnerable glass-metal seals, to cryo temperatures, for tha same reason! I'd hate them to crack... and doing this sort of thing to them is almost as likely to fracture the seal as bouncing them on a marble floor...

Regarding cables and mobile phone pickup, yes most amplifiers have negative feedback which is another way of saying that the output lead is actually connected (albeit via some attenuation) to a fairly sensitive input node. Not surprising that strong RF can get detected! From a design point of view, the series output inductor, if fitted and if suitably wound as a really low capacitance choke, might do double-duty as RF filter as well as a stability-enhancer for capacitive loads.

I have found even a basic 4-valve battery superhet (Vidor CN420a), operating from batteries, responds to mobile phone buzz if the phone is closer than 3 feet. Not tried to find exactly where it's getting in yet, but it's quite surprising!
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