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

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,

Lewm,
+++ ... 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? +++
No! please see below.

A 30dB SUT (1:31.6 ratio) has a "natural impedance" of 47 ohm when going into a 47k secondary input impedance (the phono-pre).

Since the primary impedance = secondary input imp./ ratio ^2 = 47k/31.6*31.6 = ~ 47 ohm primary impedance.

So what I now like is the 47 ohm primary *impedance* of the SUT without ANY resistive loading (other then the negligible 1.1 ohm of the primary coil winding itself...)

I hope this should clarify the matter.
Greetings,

You guys are getting interesting and funny too. Well, thank you for sharing some of this empowerment.

Messing with MCs problems, as messing with any on-going problem has a 'pay-off', otherwise no-one would bother. As long as it is fun and entertaining and not frustrating, it's jolly good entertainment.

As to the MM side of things, it also should better be fun and not any of this competitive BS like: like my 'spanner' is longer than yours...' etc.

I think a lot of phono-pres are ultimately not up to the task of really GOOD! and COMPLETE! low-signal amplification.
Just pumping up the gain without loosing some of the incredibly delicate detailed LOMC signal output is a VERY demanding task.
In this case an SUT will make a difference, or an MM in its own unique way also.

I find in my (all) SS system, MM carts generally have more 'information density' in the mid-range, than MCs provide through my phono-modules. There is something very natural and touching in how MMs handle that area. The interesting thing for me is, that *ANY* resistive MC loading makes for some of this 'coldness', experienced with CD reproduction -- and it maybe simply a more 'favourable' impedance match when using a step-up that improves on this.

With MMs the trade-of mostly (or always?) is some degree of lower-treble to upper-treble lack of definition. The sort of thing that slightly lesser recordings often might show.

With excellent recordings this 'lack' is hardly noticeable, unless in an A/B shoot-out, which comes with its own set of problems.

So I say, enjoy both! as both have there characteristic strength and weaknesses (a bit like blonds and brunettes :-)

Cheers,
Axel