MC Load Resistance

Dertonarm, Can you please amplify on your statement? For example, what would be the effect of a mismatch between the inductance of the phono input in a SUT-less connection and the inductance of the cartridge itself? I am having trouble visualizing this. Also, how would one calculate the inductance at the input of a phono stage? In almost all cases, the cartridge is "looking at" a resistor that constitutes the load. Most resistors have reactance (i.e., inductance and capacitance) at extreme frequencies but not significant at audio frequencies. If inductance is so critical for a direct connection between cartridge and phono, then perhaps the choice of resistor type is also critical, e.g., wirewounds are the most inductive types that I know of. Further, would you ever advocate adding a very low value inductor in series with the load resistor, in order to match the input to the cartridge? (That brings up another question, are you thinking about inductance in series with the connection or in parallel, where the load resistor sits?) Most of us who don't use a SUT are not used to thinking about inductance with respect to cartridge/preamp matching. Thanks.

Thanks, Axel. I am comforted to know that you like that set-up, because I never could quite understand how a 13-ohm load could be superior to any higher value resistance, using your cartridge. 47 ohms is more in the ballpark of what I would guess would work well.

Dertonearm, thanks for the tip. Unfortunately or fortunately, I modified the phono input stage of my MP1 to use an MAT02 bipolar transistor as the bottom half of a cascode, where the top half of the cascode is now an ECC99, in dual-differential configuration. This, in conjunction with the output stage gain section, gives oodles of gain, even for the Orto MC7500. (The MAT02 has a Gm of 400!) And I am very pleased with the sound quality. I guess I could use a VERY low step-up ratio SUT, just to test your hypothesis. And there are tricks I could use to reduce the gain at the input, as well, without changing the topology. (I have to do this when I use the Colibri, which puts out 1.0mV.)

Axel, Can you or Dertonearm tell me how the quoted 20 uH inductance of the Windfield was taken into account in your choice of SUTs? You make no mention of the way in which you may have used that information, and Dertonearm did not really quite get there either, in responding to my earlier question. By my calculation, an inductance of 20uH will result in an impedance of 2.5 mohms at 20 Hz and 2.5 ohms at 20,000 Hz. In an MC cartridge, this suggests that the inductance has a negligible effect on the cartridge's internal impedance at low frequencies and only a modest effect at the top-most frequencies, not enough to affect dramatically the choice of an ideal load R, if no SUT was used, but obviously the impedance will increase with frequency ad infinitum.

Guys, All of this stuff is anecdotal and subjective. Dertonearm wrote that the inductance of an MC cartridge is a major factor contributing to his finding that SUTs are inherently the superior method for the first stage of amplification of the output of an LOMC. He inferred that a simple resistive load in front of a high gain phono stage cannot properly correct for the inductive property of an LOMC. I am trying to find out how one uses that information (the cartridge's inductance as quoted by its maker) in selecting a SUT.

In another vein, Axel, are you saying that you now like a 47-ohm resistor on the primary side of your SUT? I presume you also have a 47K-ohm resistor on the secondary side. Is this correct? Thanks.

Dertonearm, Re your sentiments on the hybrid cascode, we have another subject where you and Atmasphere are in agreement. Ralph also recommended that I stick with tubes in both positions. I have no axe to grind; I know for a fact that the topology can sound very good either way. The MAT02 is pretty special in this application, so conclusions drawn using other solid state devices on the bottom of the cascode may not be so applicable. But I am a neophyte in these matters and not qualified to argue either way, except based on my own particular listening experience with this set-up. If I get the energy, I could go back to an all-ECC99 cascode and use a low gain SUT to make up the difference.

Dertonearm, There may actually be women who read this thread, so I would be careful. For example, your wife may have access to the internet. Nevertheless, this reminds me of the belt-drive/direct- or idler-drive controversy as well. But seriously, I found and am finding with the hybrid cascode that the sound was very affected by the choice of the tube in the top part of the cascode. Once I made that choice, the sound is further greatly affected by the value of the plate resistor (which of course has a critical effect on gain) and the amount of current through the circuit. (Primarily, I found that lower value plate Rs sounded better, less sterile, up to a point where the plate R = about 10X the Rp of the tube itself.) Also, how one sets the voltage at the grid of the top tube makes a noticeable difference. All of these elements greatly alter the presentation of the qualities you discuss, not to mention the similar choices that needed to be made with respect to the phono output stage. That's what makes this an endlessly interesting and sometimes frustrating hobby. (PS, I would never recommend doing what I have done to a brand new Atma MP1, which is a great unit bone stock. My own unit was VERY used when I bought it and needed a lot of refurbishing to begin with, so I let my imagination run a bit.)

Nandric, Here you invoke the categorical imperative, no doubt.