Do I need BOTH amp and pre to be sonic holography?

"Sonic Holography was one of Bob's ploy's to get people to purchase his products. These names really meant nothing."

Well, the name is descriptive of the effect and the effect does in fact work with the right gear set up properly for it.

Its merits versus other approaches or whether one likes it or not is a different discussion.

Left + right and left - right. It does work very well with the C-1 preamp and/or the outboard C-9 unit. It cancells interaural crosstalk and the sound is really good, but you must set up the speakers correctly. It's not a ploy of any sort. If you get the McIntosh pre just add a C-9 to it.

The only downside I heard with the Carver sonic holography when I used it was a noticeable loss of dynamics, mostly in the low end. It did however work as advertised if set up properly as instructed and listening smack in the sweet spot. Away from the sweet spot, the effect was detrimental.

No snake oil there. It worked exactly as advertised.

ALso I found that it worked best with more directional conventional box speakers (with a smaller sweet spot) that had coherent integration of drivers to start with, most monitors and some floorstanders. It worked with Maggie planars also but proper setup was hard.

I found it did not add anything with my OHM Walsh speakers which are essentially omnidirectional. Apparently, Carver sonic holography works best with more directional speaker designs and the effect is less noticeable with wider dispersion or omni designs.

It most certainly worked as claimed, and sonic holography is a good description of the effect-images appeared to be placed around the whole front hemisphere, and some images seemed to be startlingly close up (VERY three dimensional).

But, the effects seemed artificial and exaggerated. There was also a phasey quality to the sound. I also did not like the tonal changes--upper bass seemed to be overly prominent.