How important is the cable between the SUT and phono pre?

I know when using a cable between a MM cartridge and the phono pre it's very important to take into account the capacitance of the cable for cartridge loading.

I don't recall seeing a discussion on the importance of using low capacitance cables between a SUT and  phono pre.  

I picked up a Denon Au-340 to replace my Denon AU-320 in my system and the AU-320 has built in cables that run to the phono pre, hence my question.

Is there a way to figure out the capacitance requirement for this cable or is it not that important? Will a good shielded cable work fine?

I don't want suggestions on some high dollar cables, that will never happen. I have about 15 or 20 pairs of cables that I picked up over the years, I can always go through the pile and measure the capacitance if necessary.





My laymans understanding of the scenario is that because the MC transformer converts high current low voltage LOMC to a higher voltage low current signal exiting the transformer an interconnect with high capacitance between the transformer and MM phono is more prone to noise intrusion.

Would love to see a cite with a detailed technical explanation.

You are looking too deep into it.  This is the simplest basic transformer theory and the simple ideal transformer model is all that is required.  The problem you are having is assuming the load is a resistance but in reality it is an impedance which can be any combination of R, L or C.  By the time you get into the models that include external capacitive loads, the concern is more about how that capacitance interacts with the internal R,L and C of the transformer and not how it reflect back to the source.


No, that's not the problem I was having.  Worked through it with a friend and see that I was not correct.  Regardless, something that actually explains it would be beneficial.  I like to enhance my understanding of things, not just parrot what someone says because they said it. 

However, transformers do not reflect secondary load C to the primary.   


Transformers transform impedance and impedance includes capacitance. However, things are not as simple as just that. You have to also consider how a parallel capacitance interacts with the inductance of the transformer- and here we are talking about a resonance. This is also occurring on the primary side! Of course, I'm saying the same thing that Dave @intactaudio just did in different words.

If your EE friends tell you this isn't a thing, here's an EE that is telling you it is, just FWIW... but 'multiplied back to the source' is only correct in that there is a fractional factor involved, variable with frequency. This is really one reason I stay away from SUTs if I can help it 😁

As a general rule of thumb, the best advice is to use low capacitance cables. If you do this right, the electrical resonances involved will be so high that on the cartridge side it will be well outside the transformer's bandwidth. If loaded properly on the secondary side (such that there is no ringing) again you're off the hook. At any rate don't think for a minute that the loading on the secondary side (including capacitive effects) can't be measured on the primary side!