A question of loading...


I have just replaced my aging tube preamp with a new model. When I was using my older model with tube phono stage, I would run my Lyra Kleos and other MC cartridges with a load of 750 ohms. So, I assumed that with my new tube phono stage, which also utilizes a transformer in the phono stage and is also built into my new preamp, that the same cartridge loading would apply. I listened to the Kleos for about a week with this loading, and frankly, while it was fine, I wasn’t bowled over. Tonight I decided to experiment, so the first thing I did was to run the cartridge straight in, with no loading plugs. WOW, the increase in overall musicality and soundstage width was eye opening! Lesson learned is that not all gear is going to react the same when it comes to cartridge loading, particularly if there is a transformer involved and even if you are using the same cartridge from one phono stage to the next! An eye opener, anyone else experience something like this?
128x128daveyf
fsonic, May I just ask a question without making you angry or making anyone else angry.  As the owner of a Manley Steelhead myself, I am wondering how you achieve a load of 50K ohms or 100K ohms or "25", by which I take it you mean 25 ohms?  As you know, the max load if you use one of the MC inputs on the Steelhead is 400 ohms, and it offers choices going down from there to 25 ohms minimum.  I assume that is what you did in that case.  The Lyra website says the Etna Lambda has 4.2 ohms internal impedance, so 25 ohms would be a bit on the low side for phono input resistance and your description of the aural effect makes a lot of sense in that context.   The Steelhead uses autoformers in its MC section to achieve the various load resistances, which is a bit different electronically from using a SUT. I'm sure you know that.  I sure wish I could get hold of a schematic, because I would like to see how they use the autoformers.

If you connect an MC cartridge to the MM input, there you can have 47K ohms, but 50K and 100K are not offered.  However, if you change the fixed load resistor inside the chassis from 47K to 50K or 100K, by that means only can you achieve either of those two load resistances.  Is that what you have done?  I've actually purchased the resistors to change the max MM load resistance from 47K to 100K, but so far I have not done it.  I found the Steelhead to benefit greatly from a modification to its output stages (both the phono output and the passive linestage output), for what it's worth.

Not that it matters a lot, but I have to agree with Dover. In the conventional parlance, to increase the value of the load resistor is to decrease its load.  Capacitance is also a "load", but that is a different parameter.  In any case, I knew what you meant, when you discussed the effects of various load resistances, and that is what counts.
@lewm 
Not angry at all-in fact Lewm-you are among a handful of regulars on this Board that I rely upon on all analog matters and respect as having greater grasp of technical issues than I do. 
I previously acknowledged to Dover that he was correct and that I had misspoke as to loading. 
As you know, the max load if you use one of the MC inputs on the Steelhead is 400 ohms, and it offers choices going down from there to 25 ohms minimum. I assume that is what you did in that case. The Lyra website says the Etna Lambda has 4.2 ohms internal impedance, so 25 ohms would be a bit on the low side for phono input resistance and your description of the aural effect makes a lot of sense in that context.  
Yes, I meant that 25 ohms on the Steelhead with the Etna (and my VdH Crimson before it) sounded loose and sloppy, 50 ohms sounds ok on the Etna and sounded best with my VdH Crimson, and 100 sounds best with the Etna Lambda in terms of sounding tight and controlled without all the life being sucked out of the music, which occurs at all higher levels. The lower settings are euphonic but distorted. And yes, I use the two MC inputs only and not the MM. And I knew and agree that my use of the term "internal step ups" was sloppy and loose too (pun) as Manley refers to them as both in the owners manual (though I may be wrong and maybe they use the term "autoformer" exclusively) but as you stated, without seeing a schematic, even an informed person like you would find it difficult to explain what is going on and why. 

Ralph-thank you for your very polite and informative response. I apologize for my strong words directed at you. 
@atmasphere Ralph, thank you for contributing to this topic. What you posted was extremely informative and interesting. I certainly think that a lot of fellow a’philes can learn a lot from you.

In my case, i am still a little surprised as to why the new preamp which features a phono overload spec of 70mv rms for MC’s is so very different to my old model, I am guessing that this is high enough to not risk ringing with my particular cartridge, a Lyra Kleos that puts out 0.5mv. What is odd, and I am not quite understanding this part, is why with my older CAT phono stage, which did not use a SUT at all, that a load of 750 ohms was better sounding than straight in at 47Kohms, yet with my new model, this is definitely not the case. Presumably due to the SUT in my new CAT?? One thing, the CAT has a healthy output voltage at about 50 volts..
I still maintain-righty or wrongly-that two things are at play with loading. One can argue that they are interrelated. One is preventing ringing/overload and another is changing the magnetically induced behavior of the cantilever. 
My own misstatements about higher loading values being the same as higher loading is a common one and a common source of confusion. I think that the confusion stems from loading being nothing more than a resistor placed between the signal wires-left and right-and ground. A high value resistor such as 47K means less loading because the circuit is left relatively open. The cartridge/cantilever sees no electro-magnetic mechanical "constraint" because the resistor is to ground. Conversely, a low resistor value comes close to a short circuit/complete connection between signal and ground causing the cantilever to become electromechanically constrained. 
Ralph and others talk about the cartridge/cantilever having "to do more work" at higher loading. Ralph explains;
Of course if you use the loading resistor option, you are asking the cartridge to do more work. If you're using 100 ohms as a loading resistor, that's a couple of orders of magnitude more work than if the cartridge is driving 47K. This results in the cantilever being stiffer- the same as what happens with a raw woofer if you short it out (they are both based on the same principle of operation). This is not a matter of debate, if you feel the desire to do so, take it up with Mr. Ohm. Ohm's Law cannot be defeated and isn't open to interpretation. If there is more current flowing, it has to come from somewhere and that somewhere is the motion of the stylus in the groove. So the fact that the cantilever gets stiffer is not controversial. Anyone versed in the art knows this- Jonathan Carr and I discussed this issue at the Munich Show a few years ago.
I will freely confess that I thought the loose and flabby sound I heard with the 25 and 50 ohm settings on my Steelhead was the result of a LESS STIFF cantilever and not a too-stiff cantilever as Ralph explains above. It does make sense-once one understands the higher resistor value being to ground-that the lower resistor value approaches a short circuit and that the cantilever becomes stiffer and less damped, not less stiff and more damped. Damping is the absorption/dissipation of energy. You all know that. Why a less damped cantilever results in loose, flabby sound and a highly damped cantilever results in lifeless sound is still a tough concept for me to get my head around. I think I know what Ralph means when he speaks of the cartridge and cantilever having "to do more work" with higher loading by using his raw woofer analogy and imagining having to create an electric signal by applying more mechanical force-not less-pushing on a close to a short-circuited and electromagnetically stiffened woofer cone to generate a given amount of electrical output but still-this does little to explain why a less damped (stiffer) cantilever sounds livelier and why a highly damped (loose) cantilever sounds lifeless.