Passive & Tubed pre-amps to power amp at same time?

The Sys has a specified input impedance of only 10K, which will be too low for many tube preamps to drive with good results. For example, if like most tube preamps yours has a coupling capacitor at its output, its output impedance is likely to rise to high values at deep bass frequencies, which is likely to result in significant rolloff of the bottom octave or two with a 10K load. Also, the 10K input impedance of the Sys, as seen by the tube preamp, will actually be somewhat less than that depending on the input impedance of the power amp and on the setting of the Sys' volume control.

Perhaps the best thing to do is to get both a passive preamp not having a switch, and a separate line-level switchbox. The switchbox would select which of the two preamps has its outputs routed to the power amp, and would connect the outputs of the preamp that is not being used to nothing. A number of switchbox possibilities are suggested by me and others in this thread.

Also, regarding the passive preamp itself, and assuming that it is resistance-based (as opposed to the probably much more expensive transformer-based types), keep in mind that perceptible rolloff of the upper treble, and consequently sluggish transients, will result if the combination of cable length and capacitance per unit length of the cables at its outputs is not kept low. And if a switchbox is used between the preamps and the power amp, that would mean the total lengths and capacitances of the cables connecting the passive preamp to the switchbox AND those connecting the switchbox to the power amp.

Good luck! Regards,
-- Al

Al - That's a lot for a non-EE to digest. Thank you for the detailed additional input. Much to ponder. Might be simpler to just live with things as they are; i.e., limited usable volume control range on pre-amp with CDP (but things do sound great).

If what you are trying to accomplish is simply to increase the part of the volume control's range that is used for the CDP, consider trying a pair of Rothwell attenuators, inserted into the preamp's input jacks that are used for the CDP.

They are offered in a choice of 10, 15, and 20 db of attenuation, and balanced and unbalanced configurations. There have been reports of compromised dynamics resulting from their use in some systems, but many others (including me) have used them with fine results.

Regards,
-- Al

Al - Yes. Looking to extend the range (and "fineness") of volume control which most of the time now is limited to between 7 & 9 o'clock on my pre-amp with TEAC CD3000 as input. I was aware of the Rothwell attenuators. They were my first inclination but I was put off by reports of negative effects on sonics. The fact you found them satisfactory carries some weight with me. I understand the product option you are suggesting. The attenuators would certainly seem to be a more elegant solution than another box or two and more interconnects. As others have stated, you are a real asset to this "community". Thanks once again.