Okay, I was hoping I could go to Radio Shack and get a magic box or two, but I guess that is wishful thinking.
How about this. I have two identical Marantz receivers which I can put in "pure direct" mode to minimize their influence.
CD/DAC output to CD input of R1 (receiver 1)
Tape output of R1 to Tape input of R2
At this point I can use the remote (common to both receivers) to select Tape or CD and the output signal will switch between the two units.
Things I'm not sure of:
1) Can I feed "pre-amp output" into either another preamp or into a power amp (isn't the line essentially still at line level)? If so, that solves the issue of switching the signal going into the components.
2) Are there problems with having two amps hooked into the same pair of speakers even though only one of the amps is receiving a signal at a time?
I've got some expendable boom box test speakers for proving things out, but I would not want to screw up the amps!
I know this is not theoretically perfect, but it seems good enough for practical purposes. If I notice a difference, I can swap the connections between the receivers and the components being tested to see if my preference is still the same.
Thanks!
Radio Shack doesn't sell "magic boxes" and when comparing equipment, ANY connection between the source and preamp, preamp and power amp or power amp and speakers has the potential to obscure any quality differences. Think about some of the topics of discussion here and in other forums- people think a power cable that replaces one that is perfectly capable of delivering the voltage and current needed for a receiver, preamp or power amp and
isn't even in the signal path, speaker cabling that replaces other cable that's again, perfectly capable of delivering the signal or interconnects that are carrying low voltage audio signals over short distance, adding connections in the signal path isn't going to be totally transparent.
1.) If you feed signal to another preamp, use the tape loop- it's a fixed level and preamp output line level is for feeding a power amp. A system has several areas where the signal experiences gain and the preamp is part of the gain structure of the system. Output and input impedances need to be correct, too, and tape input is often in the 100K Ohm range while power amp input is frequently in the 1 MegOhm range.
2.) You don't want to connect two amplifiers to the same pair pf speakers.
If you want to hear the difference between two amps, using boombox speakers is not the way to do it.