[time-nuts] Clocks for Audio gear
Hal Murray
hmurray at megapathdsl.net
Thu May 10 20:49:06 UTC 2012
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.)
--
These are my opinions. I hate spam.
More information about the Time-nuts_lists.febo.com
mailing list