Henry,
If you will recall some years back in my experimentation I was running three tables side by side. I had each set up well on the concrete slab. Making nice music in their own different and unique way.
The test for structure feed back was to lower the needle on a still record un mute and crank the volume slowly. Then jump up and down beside each table searching out air pockets in the poured concrete. You're not a true audiophile until you have danced with your turntable.
I then brought out the bad boy. The Acutex 420 str. As naked a cartridge as there ever was. And I teamed it up with wiring that was unshielded except for its own poly covering. What followed was interesting.
The Jean Nantais Lenco exhibited a drone like noise. If I remember it was almost mechanical sounding. In talks with JN, I added an extra ground from the motor to the plate but to no avail. I was unwilling to make further mods to his table so that was the end of the road.
The Technics SP10 II made noise and required an extra ground. It was added from where the bolts goes into the casing and then into the preamp. This cleaned things up and it was quiet. Almost.
My former modded thread drive TNT/SDS drive with pneumatic suspension. An absolutely black silence, as black as the table itself. It revealed a veil in the music that the SP10 was making.
As we say - You don't know what's there, until you hear "it" removed.
So the 420str is a very good test cartridge - imo. If things pass with that cartridge they can only get better from there. Cheers
Have you tried testing the resonance characteristics of the granite pipe?
Granite pipe 8^0
