Best practice ways to setup decoder switch, and standalone demodulator Qs

[QuantumGuitar]

I've currently got a Sansui QRX-9001 based setup that I run the quad tape outs into the multi-channel input of my a/v pre-amp.

In the hopes of improving my phono stage beyond the 9001's outdated design while still maintaining all 3 big quad format capabilities, I have a few questions:

1. What would be the gold standard standalone (JVC?) CD-4 demodulators and how do they interact with phono pre-amps (before, after, integrated?).

2. What would be a best practice/low noise/obtainable solution for connecting a CD-4 unit, a Sansui QSD-1 and a Fosgate Tate II 101A with a single 4 channel rca output?

Bonus 3. All of the QSD-1 units I've seen have been 100V power. I'm currently using a Panamax M5400-PM and have planned to keep all the quad sources and decoders on a single isolated power zone. What would be any best practice 100V step-down transformer advice for this scenario or in general?

 

[par4ken]

2. What would be a best practice/low noise/obtainable solution for connecting a CD-4 unit, a Sansui QSD-1 and a Fosgate Tate II 101A with a single 4 channel rca output?

Look for a passive "Component Video Switch", they have five (or sometimes six) switched RCA input/outputs. Because almost nobody still uses Component Video you can find these units cheaply. For a bit more money there are powered units by Zektor. Although the Zektor's take power the inputs/outputs are switched via relays, so still passive are far as the signal is concerned. There are many posts about both here.

Bonus 3. All of the QSD-1 units I've seen have been 100V power. I'm currently using a Panamax M5400-PM and have planned to keep all the quad sources and decoders on a single isolated power zone. What would be any best practice 100V step-down transformer advice for this scenario or in general?

I recommend using either a step down transformer or an autotransformer. Hammond makes both types. This is what I use.
Hammond 196C

1. What would be the gold standard standalone (JVC?) CD-4 demodulators and how do they interact with phono pre-amps (before, after, integrated?).

I like the Marantz CD-400B, it has automatic carrier level. Others have thier favourites, often JVC or Technics. They have thier own phono preamp built in but for best (non CD-4) results you should use something else as the Demodulator limits frequency response to 15Khz.