MC Load Resistance

Hi,
looks like we are back with the SUT business...
Let ME state categorically that the Dertonarm IS RIGHT with regards to a LOMC (>=0.3mV) producing more 'natural' sound with a correctly matched SUT.

Even with a pretty modern design cart like an Ortofon Windfeld that can pretty much work OK with loads from 500 - 47k ohm it sound *absolutely* better more natural with SUT.

In this case example: 4 ohm source impedance, ~ 20uH source inductance, and 0.3mV output.

Matched to an SUT of 30dB (1:31.6) i.e. 47ohm primary input impedance going into 47k phono-pre.
Primary DCR of SUT = 1.1 ohm)

Phono-pre is all SS, and in fact MORE quite! without SUT when set to 78dB. Using the cart with SUT gives more natural 'ambience' and depth information without perceivable loss of detail what so ever.

In comparison 1k resistive load gets to 'hot' in very dynamic passages, and already too 'sat-on' with ~500 ohm. Loading with 100 ohm sounds completely dead, or as Dertonarm pointed out by using the simile of far ‘too much feedback like’ sounding.

Now go figure...

Greetings,
Axel

It is a pity, that common Phono knowledge gets buried. Of course the user will find THE exception (SUT or high gain Phono) but may I add something important:
I listened to transformers from horrible-excellent, but honestly, horrible was majority. Colored, wrong in reproduction, channel separation and so on... I did that for 3 years with various units (EAR, Kondo, endless cheaper units) and at the end of the road I use now a top unit with 1.rate studio specs. No Hype, no miracles, just measured - and compared - datas.
And before I did that, I wasn't really mad for them.
Most manufacturers have no idea about the sense behind, they offer it - more or less - to make some money, top trannies are ALWAYS expensive, there is no way out and we know from former discussions, "expensive" is the most hated word in High End
(High End but lowest price, funny eh?)
But honestly, before some readers will say: "Great" after reading that and think, that is the - cheap - solution for everything: no, it's not.
It is just one more piece in the analog puzzle.

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.