1. Home
  2. analog
  3. 128100-10021

SUTs and Resistive Loading Questions

Hello, I have a few questions about SUTs and adding parallel resistors to reduce the load impedance.

I have a SUT with a 1:15 turns ratio. As we know, the load for a 1:15 SUT through a MM/47,000 phono preamp would be: 47,000/15/15 = 209 ohms.

However, I want a load impedance of 100 ohms for the MC cart I'm using. To calculate the value of the resistor I need to add in parallel to do so:

100 ohms = Z/15/15 for a SUT with a 1:15 turns ratio. Solving for Z = 22,500 ohms.

Resistor Value Needed = 1/((1/22,500 ohms) - (1/47,000 ohms)) = 43,164 ohms.

So now, my questions...

If my phono preamp has a 100 ohms load setting, can I use that (instead of the 47,000 ohms setting and the above calculations for adding parallel resistor) to essentially get the 100 ohms load impedance I want?

Also, is there any difference in damping using the first method versus the second method? I would think not, but not completely sure.

Thanks for your insight.
edwyun

Showing 3 responses by rauliruegas

rauliruegas
9,123 posts
 
Dear @edwyun : "  In a prior setup, I did notice a difference between 100 versus 200 or 470 ohms ....Cart is Dyna 20x2L. "

The didifferences because loading is not much because the cartridge " reaction " tha's almost no sensitive to normal load changes. Those differences comes from the phono stage " reaction " to those loading changes.

Anyway,  you will follow making load changes till you are where you like it more.

Regards and enjoy the music,
R.
rauliruegas
9,123 posts
 
Dear @edwyun : "  my pre has sufficuent gain for a MC but my experience is that using a SUT with a MM pre has benefits. "

That statement makes no sense to me other that the MC stage in your preamp be a bad design, that could be but I can't know because I don't know wich unit you own.

I said that makes no sense because: how or why can you think that adding an external SUT and additional IC cables and connectors can improve or gives benefits to the quality level performance of the same cartridge signal?

Look, if I assume that your preamp has an active gain MC stage and is a " decent " design then what you posted can't be true because those additional external devices you are talking about and in a " perfect audio world " ( that does not exist. ) the best it can do is no cartridge signal degradation and NEVER an improvement in any way.

Those additional devices you want to use only can degrade the cartridge signal and NEVER can improve it: that different levels of degradation are name it DISTORTIONS, additional distortions.

If you like those additional distortions is not the main audio subject here.


Regards and enjoy the music,
R.
rauliruegas
9,123 posts
 
Dear @edwyun : It's your privilege to disagree.

R.
More to discover