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

Al - thanks for the follow up. I did some on-line reading after posting and found similar info as in your explanations for interpreting the measured impedance values and scale upper limits being multiples of 2. I can indeed take some further readings using the 200K scale setting. As noted previously, putting the Harrison Lab attenuators on the TEAC CDP outputs did give more usable volume control "range" on my pre-amp. None of my sources are tubed so if those low resistance numbers aren't likely to harm the TEAC, I'll continue to use them.

None of my sources are tubed so if those low resistance numbers aren't likely to harm the TEAC, I'll continue to use them.

To clarify, no harm (in the sense of damage) would be done even with the kinds of components I mentioned as being unsuitable for use with these attenuators. The issue with components having high output impedances, and/or output impedances which vary greatly as a function of frequency, would be adverse sonic effects, such as deep bass rolloff.

Best regards,
-- Al

A follow up on use of the -12 dB attenuators. The Harrison Labs attenuators have indeed been beneficial in the system. They provided extra control range on the pre-amp volume control when the CDP was in use as noted earlier. I did NOT think I heard a sonic benefit in this application however, just easier fine control of volume...but no negative effects, either. Recently, I had been bothered by what seemed like upper frequency distortion when playing at higher volumes (mid to upper 80 dB at the listening position) CDs ripped to hard drive. ICs from CDP to pre are Cardas Parsecs. ICs from the Gungnir DAC to pre are Morrow Audio MA-4s. Today after switching the attenuators to the DAC ICs at the pre-amp, I enjoyed a very satisfying listening session with no trace of harshness or distortion at sound levels similar to what had been annoying 2 days ago. I'm wondering if the attenuators are doing a little "tone control" - rolling off the top end just a very little bit (by increasing the impedance of the MA-4s?). Not 100% certain the cause but did order another pair of the attenuators from Parts Express so I won't have to swap them out between CDP & DAC. We'll see if listening continues to be as pleasant and free of harshness going forward. (BTW - Al, I did come across similar values as what I measured being reported on Amazon for the Harrison Labs attenuators).