... Unless the series attenuator is wired as a shunt, but then switching noise becomes a problem even with the better switches. If the switch breaks contact at all, there is no attenuation to the amp. This will cause some serious popping. ...
That does not happen if you wire the shunt attenuator as we do in the Foreplay III.
Yes, when I use the term 'shunt' I am referring to the wiring that Voltsecond shows on his page (fig1.0). I don't really don't know how else to refer to that style of attenuator wiring. The standard FPIII wiring works great. When I first built the FP I thought it was just a standard series attenuator wiring. I can see now that it is a little different.
For some reason I found the wiring scheme on VS's page very intriguing so I tried it and liked the results (as long as the switch contacts are bombproof). I liked the idea that there was a direct connection from the input to the amp grid with only a single resistor in the path and the switched resistors only on the wire leading to ground.
I remembered a previous post where you stated that these newer styles were not actually ladder attenuators, so I just refer to them as 'ladder style.' I'm still not sure what a true ladder attenuator is.