But, to answer your question, most likely the preamp, but I wouldn't be too quick to evaluate the combo without leaving the system on and playing for at least a couple of weeks. I'd also read the manuals for each to see if either or both are inverting.

desertrat wrote:

Replaced my Krell KAV 400xi with Musical Fidelity M6 amp and preamp. Noticed that the upper end seems a bit rounded off to me compared to the Krell.

If I were to replace one component, either amp or preamp, which would potentially have more impact on extending the upper range? Speakers are Vandersteen 3s.

I had a pair of the Vandersteen 3s for many years, and I have the M6PRX amp and a Audio Research LS-26 preamp.

I don't know how old your Vandersteens are, but when I went to the Treo speakers from my 10-year-old Model 3s, that was one hell of an improvement in every way, especially the upper end. The sound was good with the Model 3s, but the Treos are SO much better!

The Krell was probably a little "hot" in the upper end, while the M6PRX is more realistic and accurate, I think.

Unless your Model 3s are pretty new, the current model 3s have been upgraded quite a lot by using the same mid and tweeter the Treo use (among other things). You can call Richard Vandersteen and ask when the Model 3s were changed and how the current ones differ from yours.

You might be able to send yours in to the factory for a major upgrade.

I would suggest that you consider upgrading to the Treos, or the newest version of the Model 3.

I think the M6 amp and preamp are excellent, and that you should stick with them. I assume you are using balanced cables between amp and preamp, as this is essential for best performance.