[sdiy] dirty/clean ground again

[media.nai at rcn.com]

At 9:04 AM -0700 08/17/02, John Blacet wrote:
>
>While compared to all other analog delay circuits I have
>ever seen, the TM seems an extremely powerful and innovative design.
>I have also noted a shocking lack of bypass caps -- there are not any caps
>>on the supply pins of any of the chips.
>
>--Wrong.

Well, none of the chips have caps on the supply pins of that chip.  That's
what I meant by "caps on the supply pins".  We were discussing the use of
small ceramic caps -- particularly high frequency decoupling caps on the
supply pins of op-amps.  I apologize if my shock to their absense in your
design was unwarranted, but the circuit simply does not use them, and there
is no point saying otherwise.

>Actually, there ARE a rather shocking number of bypass caps on
>this board (12). They are 10 uF electrolytics.

Based on the schematics and the parts list, there are 5 10uF shown as
bypass caps, two other 10uF shown elsewhere, and five 10uF still at large.
>From looking at the PCB itself, it seems these five unaccounted caps are
sprinkled along the rails.  So that's ten.  Then there are four filter caps
on the power supply inputs.

>I won't get into the reasons for the type and value, but I will tell you
>>that nothing will be gained by adding any more bypassing.

I'm sure you had your reasons.  My first guess was that there was a lack of
space, which is why replacing the sockets seemed like a good idea (it
isn't).  Admittedly, I did not know about those five caps not shown on the
schematics.