MC Load Resistance

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.

Lewm,
you are quite right when you state:
...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,...

Knowing this will tell, that in my example the 20Hz - 20kHz impedance will not vary too much in terms of the 4 ohm quoted DC Resistance.
Now, what parameter(s) make for a good SUT match? --- the 1k$ question *without* listening!
Example:
With a ~'faulty VTA' cart of same make and build the SUT mentioned worked best with a 13 ohm loading resistor in primary, which produced a impedance match of 2.5 times the cart's quoted DCR.

With a new replacement cart, 47 ohm (i.e. no resistive loading) sounds better.
Therefore the next impedance match rule of (SUT): primary input impedance to be >10x cart output impedance, seems a better match. The >10* is a voltage favouring match, the 1:2.5 is a current favouring match for power transfer.

Therefore you can still figure good matching by use of resistive loading.
The first point: to have *NO* phono-pre over-load and the second point is impedance matching by listening test.

In the case of 20uH it is OK to neglect it in your CALCULATION! B U T it still makes for the better LO-MC cart match, using an SUT rather then a resistor.
It can be heard: the proof is in the eating of the pudding.

My own theory: practically ALL high gain phono-pres of AFFORDABLE designs loose micro information when amplifying ~ >0.3mV cart out puts... YMMV

Greetings,

I had not used a SUT since the early 80s but decided to try one. I ended up getting a Bob's Devices Cinemag one. I was surprised at how good it was at a moderate price[$395]. I use a Blue Circle 707 which has enough gain without it. With it I can hear detail that was not present before and can detect no downside to its use. I only read the review of it on Ten Audio after I bought it but it is very close to what I hear also. I don't really care about the technical details, just the final sound. I have not had extensive experience with it yet but so far I would agree with Axelwahl.

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.

Lewm, just a general guideline I have found very useable and giving very close to perfect results: choose a transformer which primary is about 10x to 12x the source impedance of the moving coil. Go for a step-up ratio not higher than 1:12. The resulting transformers primary will give a very good matching inductance (and resistance....) to the given moving coil.
The basis has to be a SUT which prime design goal and feature is extremely wide frequency response and extremely little derivation from phase.
Try to restrict yourself for the above recommended step-up ratio - its a kind of "royal device" when going for the best matching in moving coils.
If your source impedance is rather high - say 20 to 40 Ohms (some DL-103 clones etc, Koetsu Urushi, Clearaudio etc.) - do lower the step-up ratio to 1:4 or 1:6.
Always go for quality and low step-up ratio in SUTs - NEVER go for high "gain". The majority of the gain must always come from the phono stage itself.
The extra gain from the SUT shouldn't be as much as possible, but as little as possible.
I do use a SUT always as a matching device in the first.
The extra gain is a bonus to me - certainly not the core issue.
Thanks,
D.