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.

Dear Lewm, any moving coil cartridge does have a coils whose movement in a given magnetic field gives the output. This coil (singular - as we are looking at one channel now...) has a source impedance - that is the parameter everybody knows about and does care about. So far so good. However - any coil does have an impedance AND an inductance.
So you have TWO source parameters.
Everybody does care about the matching load resistor in the following stage to match the source impedance.
Hardly anybody does care about the 2nd parameter - the matching inductance of the following stage.
We agree about the source impedance calling for a matching load impedance.
So far so good - that is ONE parameter.
But your cherished moving coil is also calling for the matching load inductance.
Sadly this desperate call and longing is hardly ever heard...... let alone satisfied.
If you are using a step-up transformer, you do get the matching inductance as a "freebee" with the matching impedance, as the impedance in a step-up is a result of coil-windings - as is the source impedance and source-inductance of your MC cart.
Loading a given MC cart with different resistors does alter the sound. The more so, as the resistor becomes very small. Why ? - Because you increase the amount of feedback applied on your cartridge circuit.
A suitable - yet often abused way to adapt your cartridges sound to the audio-chain it is already part of.
A cartridge of overall sound lacking bass impact and control - simply load down the beast and - è voila! - here we go with a surprisingly tight bass line!
But the mid-range magic is gone and the sound is somewhat lifeless........

This is what happens all too often.

Back in the late 1980ies I thought a step-up transformer was a waste of time and quality - high gain phono stage and one link less in the chain.
Wrong.
Only (sorry......) a matching step-up transformer does offer the ideal matching (technically spoken) next and first amplification stage for ANY low-output moving coil cartridge.
As any high gain active phono stage can offer adjustable load resistor - but hardly an adjustable inductance.....

So - you are looking for the "perfect" match for your moving coil cartridge ?
It is a matching step-up transformer.
The ideal type depends on your MCs output and its source impedance and corresponding inductance.
Its that easy.

If you have the REALLY matching transformer, load resistors are no longer any discussion. Its a natural match.

All this was no question in the late 1950ies when the first low-output moving coils were introduced.
The abundance of step-up transformers being an integral part of the moving coil based phono front-end came, when the high gain phono stages emerged in the late 1980ies.

Lewm, - a further add-on to my earlier statement and more direct in answer to your questions.

- the mismatch between the source impedance and inductance of the moving coil cartridge with the following amplification-stage does result in a NOT optimum performance. This may and will mean the frequency response, as well as dynamics, timbre, most likely soundstage reproduction (= low level resolution).

- the matching inductance is only correctly obtained with a matching coil as following stage.

- I would not try to simulate the inductance with a wire-wound resistor.
Nor would I add an inductor in series.
Depending on the circuit and principle, your phono input stage may not like the idea at all.

I like looking at technical aspects in the most straightforward and "natural" way. The concept of a moving coil cartridge does longing for -and ask for - a matching first amplification stage in the form of a matching coil - a step-up transformer.
Here - and only here - he find the natural corresponding partner with exact the technical periphery and resulting inductance and impedance needed to ALLOW the moving coil cartridge to perform at its optimum.

Give it a try.
There are good reason why - even given today's high gain phono stages - there are still a lot of step-up transformers around.
Just get a good one which does match the requirements of your given moving coil.
It may open up ears and eyes.
Thanks.

Dertonarm, the use of the word 'feedback' in your posts above either has a new meaning for the term or else the term is misapplied (language issue). My theory is the latter right now.

There is an ideal loading for any inductive audio device wherein the device does not exhibit either ringing/overshoot (under-damped) or excessive rounding (overdamped).

This can be accomplished with or without a stepup transformer.

Loading can be used as a sort of tone control but is ill-advised, but sometimes very difficult to set up otherwise if the right equipment is not available (which is a 'scope and a squarewave generator). With the test equipment, the inductive device (cartridge) can be 'rung' by the square wave and the resulting waveform displayed on the scope. Without loading ringing will be observed. A load in parallel with the output of the device will cause the ringing to decrease- there will be some point where the ringing will cease altogether.

If loaded excessively, the corners of the square wave will be rounded. The debate about where critical damping lies centers around whether or not any overshoot is allowed (I tend to go for a slight amount). At this point the loading value will be only slightly higher- often the difference of only a few ohms.

A transformer can complicate the matter as the transformer can ring also. In addition, the load on the secondary will be 'transformed' by the transformer to a load on the cartridge, so if you are loading the secondary this must be taken into account. Jensen transformers has published a chart of how this is done with their transformers (they make some excellent SUTs BTW).
http://www.jensen-transformers.com/design/MC_Table.zip

Atmasphere, I took the term "feedback" for good reason.
It illustrates nicely what happens when the MC cartridges gets "loaded down" into the 10 - 30 Ohms region and gives a nice idea too about the sound you may expect to get.

The point of inductance matching in moving coil cartridge and the following step-up transformers was throughout explained and discussed when you and I weren't even born yet.

I can only recommend to every audiophile really interested to get the most out of his moving coil cartridge to give it a try with a high-class (Jensen Transformers is indeed a very good address...) step-up transformer with a suitable step-up ratio (not too high...).
The resulting sound will proof that there is more than just correct resistance loading to get the full and real sound of a high-class low output moving coil........