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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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larryi
3,997 posts
 
It has been about my experience that once you have a value above 200 ohms or so, there is not that much difference; at that point, you are not applying much loading.  That is why some phono stages, like the Linn Linto, had fixed loading at some almost universally acceptable value of something like 125 or 150 ohms.  

If you want to adjust tonal quality, such as increasing the apparent bass response, you can go with more loading (to decrease the treble response) by selecting a LOWER value, but, this comes at the expense of lower gain and a more muffled sound.  If I need a "fix" for something like excess sibilance and shrill top end, I tend to look more at altering VTA/SRA than changing loading.
lewm
13,071 posts
 
Larry,  200 ohms would be fine for most LOMC cartridges that have an internal resistance of 20 ohms or less, but there are some exceptional LOMC cartridges that have a higher internal resistance and will be affected by 200 ohms as a standard.  I think you know this, but I thought it ought to be pointed out to those who might not. By the same criterion, I don't think one can say that 125 or 150 ohms is "universal".  Once you go below a critical value, where the load R becomes much less than 10X the internal resistance of the coils, you start to roll off the top end of the frequency response and to lose signal voltage to ground.  Like you say, if the cartridge is too bright, it's best to tame it by some other method, IMO.
atmasphere's avatar
atmasphere
11,817 posts
 
Perhaps the Pass is one of those phono stages that's not that sensitive to loading.
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