In article , RJH wrote:

FWIW, my iPhone's 'polling' (not sure how, what or why) can be heard on
my hifi, FM radios, and work's PA systems in lecture halls. It's a sort
of chirping, and lasts about 10s.

We don't get any problems from phones, etc, even when using one in the same
room. This is despite a lot of the kit I use being pretty old - i.e. like
me!

I always fitted an RC at the input to amps and a full Zobel (series
inductor/resistor as well as shunt cap/resistor) to help block crap getting
in. I also put caps across all four mains bridge diodes and across the
mains input.

On 22 Nov in uk.rec.audio, Woody wrote:
In many cases putting a loop or two the speaker cable through a ferrite
ring will kill the interference dead, but have you tried buying ferrite
rings these days? At one time they were easily obtained and in many
varieties but now - lets us say rocking horse manure comes to mind.

FWIW I buy rings from CPC. I'd echo that they often deal with garbage
picked up from the speaker leads. As you only have to wind the lead though
them they are an easy fix for people to try.

The Armstrong 626 I had refurbished recently was an early version. These
were prone to clicks, etc. The first impression might be that they were
getting in via the mains. They also have a wooden lid and plastic base, so
are exposed to external fields. (Unless you line them with ali foil or
mu-metal!) But experiment showed me that it was via speaker leads. Solved
with ferrite clip-on blocks/rings.

Jim

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