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Running LOMC with MM (47K) loading

This is the way I run my Zyx 4D and my Benz Ebony L before it. I have a JLTi phono preamp which allows me to do this. I have been satisfied with this pre since buying it new. Yet I may be in the market for a new (Different) one. However some I have seen may not offer this ability. One that has great reviews also  has the loading and gain all tied together. Not sure about Herron but it may be out of production. Not sure about others. 
 
The question comes  with @Atma-sphere comments on loading and circuit stability. He contends that the loading  damps (stops) the cartridge cantilever from moving as freely as it was designed (my words) And it is better IF you can run with no loading. But that requires a stable circuit which not all have. Apparently my JLTi has a stable circuit because I have been running LOMC's this way for a 10-15 yrs. 

That said, should I require this attribute to my next phono preamp? And might I be better off to send the JLTi to Joe Rasmussen  (Allen Wright's partner) for upgrade to Pre and new Power supply?. That will be the cheapest and that is likely to be the step I take. However the question still exists. If the damping is as per Ralph's assessment, it would seem that the stability of the  circuit is of greater importance than the ability to have a lot of loading options with unstable circuitry. Another question, Is loading a band aid for a  circuit which is not at an optimum? I am not an electronic tech so I am not  looking to stir the pot but  for my own  understanding  Thanks
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lewm
13,168 posts
 
audioguy, There is nothing sacred about 47K ohms; it's become the standard for MM cartridges by default.  In fact, many have found that at least some MM and MI cartridges sound best with even less of a load, like 100K ohms.  ("Less of a load" means higher load resistance, and vice-versa.) Likewise, there is no rule that says you cannot try loading an MC cartridge very lightly, with the 47K option if your preamplifier provides for it. (In many cases, the needed gain for LOMC in a phono stage is achieved by using a SUT.  With a SUT, it may not be possible to achieve a load resistance as high as 47K, if the SUT is connected to an MM input with a 47K resistance load a priori, because of the effect of the transformer on the load seen by the cartridge.)  You noted that the manufacturer of your Hana recommends "greater than 400 ohms".  That certainly allows for ANY load R above 400 ohms. Which means there is no penalty associated with much lighter loading.  What Artemis refers to is the concept that loads much below 47K on an MC, like 400 ohms on the Hana, are mostly for the benefit of the phono stage circuit. I will let Atma-sphere or anyone else explain that in better detail. 


Wow, that's big news, to learn that the VTPH2A is out of production and not to be replaced.
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cleeds
5,970 posts
 
larryi
Quite a number of experts say that loading does NOT supply physical damping of the movement of the cantilever but it supplies electrical damping that reduces ringing of high frequencies ...
That's interesting. Can you please identify some of these experts?
larryi
4,055 posts
 
Rothwell, a company that supplies step up transformers said this somewhere, perhaps in their "white paper" on their site.  Vandenhul says that in their FAQ section of their site.  I think Jonathan Carr (Lyra) has also said this, but, I cannot recall where.

I don't see any mechanism for the electrical loading somehow affecting the mechanical movement of the cantilever.  The loading acts as a voltage divider with some fraction of the signal diverted through  the resistor to be dissipated as heat.  I don't see any kind of feedback mechanism for an induced current in the coils causing a magnetic field that interacts with the magnets in the cartridge.
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pindac
2,864 posts
 
I have used a LMOC on a Valve Input/Output MM Phonostage.
From a Audible Perspective, the marriage of the Two Devices delivers a prentation that is Rich and Voluminous.

As for a Presentation it suits 'IMV' non complex music combined with female volcals.
It also worked quite nicely with a Male Harmony with Harmonica and Acoustic Guitar.
With ECC81 Valves as a Input, it was Volume Control Hungry to achieve the Listening Levels I prefer, and on a few tracks, the Volume was not enough and the replay was a little wanting for extra Volume.

Put the SUT in place and the same Cartridge becomes a very airy detailed device, that lends itself to all Music Types.
The Volume Control is happiest when set at at approximately half rotation and this leaves ample more for when required.

I have not got a Problem with the MM Stage minus SUT.
I have got a Cartridge that can wear two costumes.
One version is a MM only Cob Horse with a Cart in Tow, and the other version a SUT enhanced performance Flat Race Horse released from the Stalls.     
lewm
13,168 posts
 
Pindac, What are you saying?  Seems you are saying that if gain is insufficient, then your cartridge doesn't sound its best.  Which is almost certainly true. Clearly, the ECC81 (also known as 12AT7) substitution produced overall phono gain that was not adequate, but it would help to know what was the tube type for which the phono stage was designed. Just because it is so commonly used in phono stages, I am going to guess it was the ECC83 (also known as 12AX7).  If you did sub a ECC81 for a ECC83, it is no wonder that didn't work well.  The ECC83 has over twice the gain of an ECC81, and also the latter tube requires more plate current than an ECC83 to sound its best.  So you loaded the dice against the ECC81.  If you then added a SUT to the input of the ECC81, perhaps that worked better, because you restored the missing gain.  (I think you are also saying you run an LOMC cartridge into an MM phono stage, implying a stage with not more than 50db of gain and probably less, even when the input tube is the one for which the circuit was designed, plus or minus a SUT.) Other things, like phono input load impedance also change when you add or subtract a SUT, and that too affects SQ.
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