thanks for mentioning it. but i'd like to build one myself - that's the whole point
What are you waiting for? It does not get any simpler than passive preamp.
that's what I thought but then it seems there are a thousand ways of doing it. screened vs. non screened cable, ground to chassis vs. not ground to chassis, make before brake vs. brake before make switches, keep grounds separate vs. not keep them separate ......
i guess i'm looking for definitive answers ... and i probably won't find them
Cable should be screened. However, if you have a metal case connected to signal ground then you can get away with twisted pair as the case acts as a screen. Never, ever, try to use separate wires several inches apart as in the unit you showed us - it guarantees good magnetic pickup.
If you have a metal case then it probably ought to be grounded (to signal ground). If you plan to use twisted pair then the case must be metal and it must be grounded. If grounding then there should be one connection from the case to the signal ground (i.e. socket grounds should be isolated from the case).
Switches should be break before make unless you want to short different source outputs together. Some people may suggest using make before break to avoid switching clicks, but the correct solution for this is to use ground leak resistors and coupling capacitors.
I would not bother to switch grounds, but some people prefer it.
If you have a metal case then it probably ought to be grounded (to signal ground). If you plan to use twisted pair then the case must be metal and it must be grounded. If grounding then there should be one connection from the case to the signal ground (i.e. socket grounds should be isolated from the case).
Switches should be break before make unless you want to short different source outputs together. Some people may suggest using make before break to avoid switching clicks, but the correct solution for this is to use ground leak resistors and coupling capacitors.
I would not bother to switch grounds, but some people prefer it.
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