Cartridge Loading.....Part II
I read last night the below noted discussion with great interest. It's a long post but worth the effort and I found it interesting.
It started me thinking about the amount of loading on my moving coil cartridges. Years ago I purchased my first MC Cart, a very nice Benz Micro Glider, medium output of 0.5 mV as I recall. At that time I inquired about loading here on Audiogon. I was convinced, via discussion, by another member, that 300 Ohms was the magic number, so I thought.
Time moved onward and my second MC Cart is currently a Lyra Delos, again medium output 0.6mV. Both carts had Boron cantilevers', 6 nines oxygen free copper coils and line contact diamond stylis. When I set up the Delos I did not change or even consider 'loading' changes. That was a grand mistake.....
Well, thanks to this specific thread I started to second guess myself . (you can do this when retired and more time is on your hands....)
My take from this recent thread is as follows. Load at 100 Ohms or at 47K Ohms with a quality MC cartridge. I opened up my Conrad Johnson EF1 Phono Stage this afternoon. Found it set at 500 Ohms loading. 100 Ohms is not an available setting. Damn...All these years I've been running the wrong loading, and on two carts, back to back... I don't recall why I set the loading at 500 Ohms. Faulty logic.
I reset the loading to 47K, buttoned things up and called the wife in for a listening session. Sure as heck both of us noticed the highs were crisper and more 'apparent' than in the recent past. Not a huge difference, but yes, a difference.. Hard lesson learned!
So, you smarter folks on this site might banter amongst yourselves, but in reality there are those of us, behind the curtains, reading and listening! I just wish I hadn't wasted all those years listening to the incorrect load setting!
Ending with a sincere thank you very much!!
Lou
OK... lets try a different tact since i do not think ground (be it virtual or real) matters in this situation. I am simply relying on Ohm and Kirchoff for this ideal case. Take a 30Ω cartridge and hook it up to an ideal voltage amp and then another one and hook it up to an ideal current amp. Now take two AC microamp clamps and monitor the current output of each cartridge. Will the currents be the same for each cartridge? dave |
Ralph, I just had a “duh” moment. Sutherland describes the input of his Loco and Little Loco as a “virtual” short circuit. I had heretofore interpreted that word in its more literary sense; virtual meaning “nearly “or “close to”. Thanks to your input, I now see he means it electronically (virtual). I also see that nearly all current drive phono stages do use an op amp input. The BMC MCCI being an exception. It connects the cartridge output to an the emitters of array of discrete transistors. |
@lewm Transimpedance preamps have to use opamps since that is the only way to get a virtual ground. You can use discreet opamps as those do exist (a friend of mine designed his own) but you do need an opamp to pull it off.
@intactaudio I doubt it but that depends on the actual impedance that the cartridge is driving in either case. |
I think it depends on the individual design. I know from first hand knowledge that the BMC & ESE Nibiru react differently with different cartridges, but on the other hand I have a bespoke current sensing device built by a cartridge manufacturer that is superb across all my cartridges ranging from 3-40ohms internal impedance. Also I recall the current sensing Goldmund PH2 sounding superb across a variety of cartridges, regardless of internal impedance of the MC. |
