[time-nuts] Clocks for Audio gear

[Hal Murray]

dan at irtelemetrics.com said:
> One interesting note however. Years ago we had a standard old 4040  ripple
> counter in our shop that displayed a low occurrence of jitter  of several
> times it's input frequency period at it's lowest frequency  output (Sort of
> what you are describing below). I wish I had the  numbers handy, but the
> output would be good for most of the time, then  every once in a while it
> would jump to a longer delay. It was hard to  catch with a scope, but when
> we measured every single pulse width it  showed up fairly well. The high
> speed clock (A TTL OSC in a can) never  skipped, as far as we know. We never
> did figure that one out. From what I remember we switched IC  manufacturers,
> and the problem when away. 

I expect ever old timer who did serious glitch chasing 25-30 years ago has 
similar stories.

Mine involved a dual port RAM, 16x4.  I think it was a 74S189.  It was made 
by many companies.  Chips from one vendor just occasionally screwed up.  We 
were using them in FIFOs on ethernet boards.  (They were probably used other 
other places too.  I was worked on networking.)

Back then, most large electronics companies had incoming inspection and 
qualification groups.  I remember stories of somebody contacting that group 
for help and getting a response of roughly "That's why we didn't qualify 
them."  (We were a research group.  We purchased small batches of chips 
wherever we could get them without going through the official qualified list.)


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