Quirks of the old DSS
 
                                                             Ravi Kochhar
                                                             June 19,1996
 
        As the design of the new DSS (DSS-III) takes shape, I have  tried
   to  list  some quirks and shortcomings of the old design (DSS-II) that
   could be improved in the new one.  There is  nothing  very  new  here,
   just  a list of minor things that could be better.  Please let me know
   if you know of any other such "features".
 
 
        (1) Clock noise feedthrough problem.
 
        In the DSS-II, whenever a waveform is played out via the  general
   waveform  buffer  (GEWAB),  there  is a small DC offset at the output.
   This DC offset is of the order of 5 mV, and varies from one DSS to the
   next.  There is also a very high freq.  component in the output of the
   order of millivolts.  This DC offset and noise are  best  observed  by
   turning  the  GEWAB  output  On and Off repeatedly while observing the
   output on the scope.  One of the options in the DSSTST program (option
   23, then 1 then 5) is designed specifically to observe this.
 
        Dick felt this was clock noise feeding through, but  attempts  to
   eliminate it were unsuccessful.
 
 
        (2) Attenuator switching artifact.
 
        In the DSS-II, whenever the attenuator is switched from one value
   to  another,  a  small  "click"  appears at the output.  Dick may have
   succeeded in eliminating most of this, though I forget how he did it.