We've had several ZYX carts in our system with both the copper and silver coils:
- UNIverse
- Airy 3
- Airy 2
- a beta test model that was never released to the public
We also had a gold coil UNIverse.
In all cases...
COPPER COILS
Sound fastest, most lively and dynamic, closest to the immediacy of real instruments.
SILVER COILS
Sound smoothed, slowed, relaxed, somewhat like a woodbody Koetsu. They don't necessarily "go better with tubes". That's a matter of taste, not sonics. (Our amplification is nearly all tubes and we prefer the more lifelike, less constrained sound of the copper coils.) The silver coils do sound somewhat like what people think of as a classic tube sound (those people haven't heard tube gear like our Doshi components.)
GOLD COILS
Sound like the silver coils but considerably more so, almost "syrupy" smooth.
***
These differences are not explained by conductivity or any electrical property. They are, however, consistent with differences in mass.
Copper is less massive than silver, which is less massive than gold. The same length of the same gauge wire is used in every cartridge, therefore, the moving mass on the cantilever will be lowest with copper, higher with silver, highest with gold. An increase in moving mass acts to slow a cantilever's response time and attenuate its peak amplitudes. It takes longer to accelerate a higher mass.
It was my guidance that led SORAsound to stock the UNIVerse primarily in copper coils, with silver coils stocked in lower numbers and gold coils by special order only.
I also advised Arthur Salvatore to demo the copper coil UNIverse and skip the silver. He heard the silver first and was not overly impressed vs. his copper coil Airy 3. It was only when he heard the copper coil UNIverse that he understood what all the fuss was about.
Your tastes are yours so choose the sound that appeals to you. Hope this helps.
P.S. The same principle explains why high output ZYX's (or most any other MC) sound tamed, smoothed and less dynamic compared to the low output version of the same cartridge. To double the output ZYX doubles the length of the coils. More wire = more moving mass = slowed responses. For this reason, SORAsound does not stock the higher output version of any of the higher models. Most people purchasing an Airy 3 or above have sufficient phono amplification for a low output cartridge. If they don't, their money might be better spent on an improved phono stage than on a costly cartridge with inherently limited perfromance.
