Pass XP-17 and Hana ML loading question

You are not the only one who reports the result that changing the load resistance by 20,30, 40 ohms in the already low resistance region (say, below 1000 ohms) makes a critical difference, with a LOMC cartridge. All I can say is, I never have understood such reports. It runs completely contrary to my experience. in my experience, yes, there is a very slight difference between very low load resistances and 47K ohms. However, the differences are mostly that the highest resistance sounds a little more lively to me. I certainly have never heard a difference between say 200 ohms and 250 ohms With any low output moving coil that I have ever owned. This is certainly not to say that you are wrong or misguided. It probably has something to do with the design of the phono stage, although I confess my experiences are the same with any of three or four phono stages that I own, some of which are solid state and some of which are tube Types.

There is one exception:  As you may know, it is optimal for the ratio between the internal resistance of the cartridge and the input impedance of the phono stage (which is largely determined by the phono load resistor) to be related by a factor of 1:10 or better.  For example, for an LOMC with an internal R of 10 ohms, you want to load it with at least 100 ohms or higher resistance (which is why even 47K ohms is fine). The reason is as that ratio gets lower than 1:10, you begin losing more and more of the cartridge output (signal voltage) to ground.  So the coupling becomes less and less efficient.  But if your phono stage has an excess of gain, that wouldn't matter so much.  What also happens however is that as the ratio gets lower, you begin to preferentially lose treble, because of any capacitance at the phono input stage.  (All gain stages, both tube and solid state, present a tiny capacitance at their inputs, unless the input is a cascode. There is also cable capacitance.) And the sound gets dull. (Which is why I was so surprised that you say you lose treble when R goes to 47K ohms. Should be the other way around.)

I don't have much experience with phono stages 35 years ago I had integrated amp that had dedicated phono input.  So far I tested Schiid Mani and Mani2 they are ok sounding but noise level was outrageous at 66db gain. Next I got to deal with XP15 and now with XP17. All I know about it is what I'm learning by dealing with the issue now.

Yes, circuits are diametrically different that is a fact, but loading the cartridge should have same effect on cartridge performance , sound of it at least on the dynamic level should be similar to the loads on 15 at least in the characteristic of the sound. what I’m getting on same load is half of bottom end. Does it make sense to you ??

@ssg308 Loading the cartridge causes the cartridge to have a stiffer cantilever as you are asking it to do more work. There really should be no need for this anyway since the main reason to use a ’loading resistor’ is, as @lewm pointed out, its really for the benefit of the phono section.

The cartridge is an inductor and the tonearm cable has capacitance. Since they are in parallel, an electrical resonance is created. With the Hana its quite high- 2-3MHz. That’s Radio Frequency territory and so when that resonance goes into ’excitation' (in radio parlance) its RFI being injected into the input of the phono section!

Some (most) phono preamps don’t like that and won’t sound right until the RFI is eliminated. You can do that by placing a resistance in parallel with the resonance, detuning it and thus preventing RFI. Hence the loading resistor.

Always try no loading and give the cartridge enough time to break in. Also make sure your setup in the arm is a good as it possibly can be.

If the phono section is properly designed (IOW the designer understands the implication of an inductor in parallel with a capacitance; electronics 101 FWIW...) then that will be the best you can do. Loading the cartridge will simply cause it to lose high frequency tracking ability as the cantilever gets stiffer and may cause the arm’s mechanical resonance to be outside the ideal 7-12Hz range, impairing tracking.

@atmasphere Wow you changed my perspective how I look at the problem ! great let me read it again so it can sync in  and I'll try to experiment a bit and try to load it with different resistance and see how it effect it. BTW I  tried 47k and it sounds terrible.

Have you tried a 47K ohm load with any other typical LOMC cartridge, ever, with either of the two Pass phono stages?  What was the result?  Thx.  Also, can you define "terrible"?  Do you mean that the treble was rolled off or missing, as you mentioned earlier?