Dedicated phono-pre for MM only?

As in other audio areas here there are good, regular and bad designs.

Damn straight. Couldn't have said it better myself.

Hi Kirkus,

because the side-effect of the twisting is an increase in cable capacitance, which is exactly what we DON'T want for our MM cartridge.

This is fascinating for me right at this moment due to the fact that I have just mounted a Garrott P77 MM cartridge to my Continuum Copperhead arm which has balanced input terminations into the Halcro DM10 preamp. The tonearm wiring is fine gold (or copper) uninsulated Litz type wiring (I think), which is very tightly wound together to reject the noise (hum) to which you refer. This seemed to work for LOMC cartridges such as the DV1s and Universe (which only produced a slight hum when the volume was turned up considerably), but fails miserably with the MM which produces an incessant hum at any volume.
The question has been asked of Mark Doehmann if he has listened to any MM cartridges through the Cobra and Copperhead arms as none of the dealers believe anyone has actually mounted a modest MM in such exotic and expensive arms?
We are still awaiting the answers but your statements are intriguing indeed.
What do you venture, would be a solution to this problem?
Regards
Halcro

Kirkus, Thanks for your patience in preparing a detailed response to my questions. Your take is very interesting and thoughtful. Meantime, I am wondering whether we should all be beating the bushes for vintage phono stages to use with these vintage MMs. But that would partially negate the premise that we can get more out of them now than ever before with modern well designed preamplification. Here are low-priced products that jump out at me as being possibly well suited to MMs: the new K&K, the Aqvox (SE for MMs, balanced for MCs), the Herron dedicated to MM and now out of production, any of the Hagerman products (I have high respect for his design capabilities), the Allnic products (they add on a SUT for MCs, so maybe they would work well for MMs, especially the H1200), the Whest2.0, possibly older Audio Research phono stages (maybe a tweaked SP3 would be great). Raul's 3160 may be at the top of the heap if price is no object. Any other ideas, guys?

Kirkus,
y.s.:
>>> I feel that in a high-quality phono preamplifier, ALL harmonic and IM distortion should be completely and totally buried in the noise floor, which in itself should be very low. Yes, low-order and even-order products are less disconcerting to the ear . . . but who wants any of it at all?"

Some would not agree with this necessarily, since other then in digital designs, harmonic distortion is never buried in the noise floor completely.
It seem current understanding that harmonic distortion should rather RISE evenly (even- and odd-order equally) with increasing output, rather than then decreasing with higher output. (Output rise as from cart input rise)

Two notable designs come to mind by PassLabs (SUSY, Super Symmetry) and the 'cyclotron' (re-invention) by the Thorens TEM-3200 mono blocks have proved that to be correct.

Item: 'ground contamination' as you pointed out is more of a challenge then maybe generally accepted? And we are not talking of major ground loops.
I is VERY difficult if not impossible to prevent some potential differences occurring in components (and amongst each other) during all states of operation. So they best possible directed by use of e.g. star-ground schemes. The point is, there are still caps (to ground) involved and caps have power factors, creating a far less 'clean' signal path then the dedicated (-) in a balanced design.

The noise floor of my ML326S is below 90dB (balanced). I think the issue is the 'tonality', influenced by 'combing out' harmonic distortion selectively. It is why even a MUCH noisier single-ended design often will sound 'better, more natural' then does a balanced one. (I speak from experience)
The trade-off is most always balanced = more dynamic, and 'cleaner' vs. unbalanced = better harmonic completeness, more natural sounding.

As to hum caused by 'unbalanced' MM cart output impedance. Well, I think that the more expensive carts we are speaking of (Raul mostly), those have always excellent channel balance, often better than more main-stream MCs with an e.g. <1.5dB spec.

I run MMs into my (balanced) ML phono-board and have no discernable noise (ear to the speaker)!
This at elevated listing level setting ~ 45 (max = 80, grading in dB steps).
Adding 35dB (level 80, that would destroy my ears first, and speakers next!) I can practically NOT hear noise from the listening position (this @ 60dB 'normal' daytime background noise).

I guess, ML is very good at what they do with their balanced designs ---- however, tonality and 'live like' emotionality is not exactly their forte.
One always seems to find that with 'noisier' and most always single-ended designs.
That's where I see the trade off.
Balanced = Hyper-clean and dynamic vs. unbalanced = naturalness, less clean, and better harmonic completeness.

All is of course subject to some generalisations and subject to levels of degree.

Axel

This seemed to work for LOMC cartridges such as the DV1s and Universe (which only produced a slight hum when the volume was turned up considerably), but fails miserably with the MM which produces an incessant hum at any volume.

Halcro, please understand that I mean no disrespect to Bruce Candy or the namesake of your moniker . . . but unless the Continuum tonearm's wiring scheme is unconventional (in a connection sense, not just in a twisted-wiring sense) or defective (i.e some metal tonearm parts accidentally ungrounded) . . . then the problem is your preamplifier, and the manner in which its input stage is designed.

There seem to be many designers who look at balanced input stages (both line, phono, and microphone) purely as a pair of opposing voltages, not balanced impedances . . . and its amazing how many otherwise top-notch pieces of professional and consumer audio gear are very intolerant of the slight impedance mismatches that I describe. Another example of this would be the work of Douglas Self . . . a designer who I greatly admire and find much of his work invaluable . . . but simply cannot agree with his approch to designing balanced input stages.

But hopefully its just something silly like an a missing/loose ground wire somewhere, and my little diatribe is all for nought.