-=> Roy J. Tellason said to Greg Mayman
 -=> about "IMAGE FILES" on 12-25-03  04:06.....

 RJT> I know that there's a whole mess of different kinds of optos out
 RJT> there,  and I haven't looked at what there was in quite a while.  Do
 RJT> you happen to recall who made them?

Not after that length of time. Although if they had worked as we
wanted them to, I might have remembered them...

 GM> According to the specs we should have been able to use them as
 GM> audio level controls, but we found they had a most peculiar type of
 GM> distortion at low levels.

 RJT> I would imagine so.  A little bias should fix that,  maybe?

.                    +-------+
. Audio in ----------|  FET  |------- Audio out to 1K load
.                    |       |
. control DC in -----|  LED  |------- DC out
.                    +-------+

The idea was to use the DC through the LED to vary the resistance
of the FET and thus control the audio level, but there was a
strange sort of non-linearity like nothing I have ever seen
before, that almost looked like peak crushing with a time delay.

The units were rated up to about 500v, so they could be used on
220/240v mains switching. Obviously they weren't intended for low
level audio control...

From Greg Mayman, in beautiful Adelaide, South Australia
   "Queen City of The South"    34:55 S  138:36 E

... Adversity reveals genius, prosperity conceals it. - Horace
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