In article
,
John Byrns in sci.electronics.repair wrote:

In article ,
David Powell wrote:

In article
,
" in

Hi
Copper Oxide have the advantage for things like meters
and battery charges because they have a low forward
voltage drop. The primary problem is that it has a very low
reverse voltage. Even in charger applications, it took
a stack of many junctions to hold off the reverse voltage
of a 12volt charger.

Their downside for meter use is low bandwidth. Fine for a 50 / 60 Hz
electrician's testmeter, useless for audio. Often way off at 400 Hz.

I thought the rectifiers used in the old VU meters, as well as various
telephony applications, were Copper Oxide? If Copper Oxide doesn't work
in audio frequency applications what sort of rectifier stacks were used
in these audio applications?


Dunno about old VU meters, but my guess is that they're rather
different to the meters and battery chargers that were the topic, in
that there will be amplification in the system. Given that, whatever
the response curve of the widget is, it can be linearized as necessary
with appropriate filters. My comment described a characteristic of
the nekkid rectifier.

It's not that they don't work at audio, just that they will only be
accurate over a very restricted frequency range. Not that I've a high
opinion on VU meters as used in typical consumer electronics, unlikely
to even equal the accuracy of my car's fuel tank contents gauge.
Might as well wire a filament lamp across the speakers and measure
with a light meter.

Regards,

David P.