MC phono stage without transformer?

Here we go. Raul, I disagree with you on amplifier output impedance, because an output Z of 0.1 ohm is usually achieved by using gobs of negative feedback, which introduces distortions across the entire musical spectrum that are far more objectionable than the imagined result of speaker frequency response anomalies due to higher output Z. Moreover, the goal you set eliminates most tube amplifiers. I think the amplifier/speaker interface is VERY crucial to accurate audio reproduction, but I don't think one should approach the problem by setting any arbitrary "rules" regarding impedance. If I could do it, my "rule" would be that all speakers must have a flat impedance curve at about 16 ohms across the audio spectrum, but it ain't gonna happen. In summary, your rule for amplifier output impedance raises a bunch of additional questions for debate.

"...I don't think one should approach the problem by setting any arbitrary "rules" regarding..."

This is what this whole thread has become about. In this relative world we live in there are simply no absolutes. At the risk of this becoming an absolute, having first accepted this, we can have inteligent discourse about the effective relationships involved. I think that Lewm's impedance "rule" is a perfect example. Many of the norms in speaker design that have become acceptable are at least as compromised as deeming transformer use in phono stages acceptable. Having said that I think that Raul's point re: the implied messages to the industry we endorse is an excellent one.

Raul is incontrovertibly correct about RIAA EQ. **Anyone** who says otherwise is not only wrong, but likely trying to sell you something :)

If you want to hear the recording engineer/musician's intention, your RIAA EQ should be correct. Incremental differences of a fraction of a db are readily audible, as the EQ covers a spectrum rather than a single frequency.

Again, just as in the case of detail, the better your system the more profoundly you will experience this. BTW I do not equate the cost of a system with how good it is!

Dear Lewm: +++++ " is usually achieved by using gobs of negative feedback " +++++

IMHO is up to the designer know-how and I don't want to open a new " door " on this thread about, suffice is to say that you can do it not necessary with " gobs of negative feedback ".
Now there is nothing wrong with feedback, in many circuit stages, if you know how to use, how to apply, where to apply and in which quantity.

I don't think about " rules ", what I'm trying to say is that a low output impedance in any amplifier is a desired one for a miimum speaker/amplifier mistmatch and for a better quality performance but like anything we always have to deal with trade-offs.

+++++ " If I could do it, my "rule" would be that all speakers must have a flat impedance " +++++

I could agree with this part of your " rule " ( only this part that it is not what you are saying. ), this characteristic can help to a better sound reproduction quality performance.

Regrds and enjoy the music.
Raul.

This thread seems to be veering down another path. I think it would be good for interested readers to go back and read this thread. Lots of good stuff!

What Makes a Good RIAA or Line Stage?