Choosing a MC phono preamp for my new cartridge

Here's a few tips:

If the phono section has a loading switch for LOMC cartridges, its likely to generate more ticks and pops. This is because the loading is for the benefit of the preamp rather than the cartridge (the opposite of what most audiophiles think). There is a radio frequency electrical peak created by the cartridge inductance and the interconnect capacitance. If driven into excitation, this peak can overload the input of the preamp if the preamp has a poor high frequency overload margin. To solve this, loading resistors are used (hence the switch) but you pay a price: you're causing the cartridge do drive a lower resistance, thus making it do more work. There's no free lunch here; this means that in turn the cantilever of the cartridge becomes stiffer.


If the phono section does not need loading of course the cartridge is then driving 47K so the cantilever will be more able to trace high frequencies. If it does not need loading then it has good high frequency overload margin and so won't make ticks and pops because it won't be overloading.


Its worth it to check with the manufacturer on this stuff. If they don't know what you are talking about or think its a bunch of poppycock then you know that the phono section wasn't designed to take this electrical peak into consideration.


FWIW its much harder to design a solid state phono section to do this right than a tube phono section. The reason is a tube phono section usually overloads at its output before the input overloads. A solid state phono section, if presented with a 30dB peak at its input is likely to have the input circuit overload.

More on how this electrical peak works:
http://hagtech.com/loading

@atmasphere 

Thanks. I may have asked this before, but do you teach? You have a knack for making things understandable. As One who is not at all knowledgeable about what processes take place in the equipment, I really appreciate your posts

I may have asked this before, but do you teach?

No. I appreciate your comments; I put myself through engineering school by repairing consumer electronics. I somehow seemed to have a knack for explaining technical issues in layman's terms so I got asked to do that a lot when customers picked up their repaired equipment.

I have to say Ralph that I always always learn something new from your posts, but I you got me confused here.

Are you saying that the loading with a switch is worse than loading direct with resistors in the circuit because of the electrical condition of the switch

Or you are saying than with the switch you have not the the granular adjustment you could have with resistors and you have to go through steps of loading that might not be optimal

By the way off topic but I learned recently that for the MP-1 to sound perfect in my rig needs 2, ideally 3 hours warm up. With 3 hours warm up it gets completely out of the way, totally different than for example after only 1 hour, on MY system.

Are you saying that the loading with a switch is worse than loading direct with resistors in the circuit because of the electrical condition of the switch

Or you are saying than with the switch you have not the the granular adjustment you could have with resistors and you have to go through steps of loading that might not be optimal

@luisma31

Neither. I am saying that if a loading switch is present, its an indication that the designer of the preamp did not take the electrical peak that is always present into account. He may have even been thinking that the loading is there to prevent ringing of the cartridge, which it doesn't (the inductance of the cartridge is so low it simply won't ring at audio frequencies).