Mismatched preamp and CD player?

I would place them between the CD player and the preamp. BTW, I use an attenuator between my tuner and preamp to tone down the volume. Give them a shot. Like I said, you can always return them if they don’t do the job.

Sounds like too much gain in your system- OP.

jafant - That seems to be the consensus, but I don’t understand why? This same gear has driven Magnepan 3.6s (10years ago) and I don’t recall the issue coming up.

George - I don't suppose placing the SYS between the CD players and the Adcom preamp would address the problem and allow me to use the phono stage of the preamp for a turntable?

could I somehow use the phono stage of the Adcom GTP-500?

Yes just switch to it from the tuner, still the tape out goes into one of  SYS inputs 

Cheers George

georgelofi has the best low cost solution.

" What is likely causing too much system gain?  This gear has been used together before (not the MMGs but other Maggies) and I don't recall the problem."

Its not that any one component has too much gain as a design flaw, you just have to be careful when you match components. In your case, the 3.6's are a much more difficult load to drive than the MMG's. Your line level amps needed to deliver a lot more power to your power amp to get the same volume out of the 3.6's than your MMG's. This makes the volume control much more sensitive.

It's also worth noting that there is more than one way to fix this issue. If you know what you're doing, swapping out any one component can fix it. For you, that's not a practical solution, so that's why a passive volume control was recommended. In your case, this can also lead to a substantial increase in sound quality by eliminating your active line stage (the GTP-500). Doing this should help with whatever brightness issue you have, that still remains after the speaker are broken in.