Loading my XYZ 3-S ??


Greetings all
I have a XYZ 3-S which is driving a pair of S&B TX-103 transformers, into a Atma-Sphere MP-3 pre-amp. I have the transformer set at 26-db gain. I was running them without any loading resistors (107 ohms load), till I read that Doug Deacon has his loaded at 7.2 ohm.
I installed a pair of 3.3K into the pre-amp after the transforms, the sound because much more organic, but I seem to have lost a lot of the highs, and need to turn the volume control up more to get the same loudness out of my speakers.
Question?
Do I have the cartridge over dampened or am I just use to listening to the cartridge under-dampened?
bryanp

Showing 3 responses by nsgarch

FWIW (I've gone into more detail as to 'why' elsewhere in these threads) I've found that the best baseline (starting point) for then establishing the optimum (best for your ears and your system) cartridge loading is 25 times the internal coil resistance (sometimes referred to as output impedance) Then try your listening tests within a +/_ 50% range of that number.

For example, the Airy 3 SH is 8 ohms (the SL is 4 ohms, but you didn't say which one you have.) So 25 x 8 = 200 ohms is your center point. (And until your cartridge has broken in for at least 100 hours, don't bother screwing around, just leave it at 200 ohms) The range to explore after break-in would be from 100 ohms to 300 ohms.

First make sure VTF, anti-skate, overhang, and SRA are correct. Then I always start at the lower end of the range and work up, to make sure I don't miss anything. At the lower end, you can basically expect the bass to be there OK, but it will be a little muddy or undefined. At the upper end of the range (and beyond), the bass will be lacking, and the mids and highs will stand out, maybe even a little glarey or grainy. Then you back down 'til the bass just comes back full and tight, and you're there. This will be the point at which your cartridge is giving the best energy transfer and the flattest response.

My pet peeve is with those who set the load too high. Sometimes as high as the standard MM 47,000 ohms! I often find these are the folks who tilt their tonearms backward because (though they probably don't realize it) doing so will roll off some of the high frequency imbalance they've created with too high a load setting. Now honestly, what cartridge maker in their right mind would install the stylus in the cantilever such that in order to attain the correct Stylus Rake Angle, you'd have to tilt the cartidge backward? Really!!
If you are using a step-up transformer before the preamp, then the transformer INPUT impedance should be equal to or higher than the cartridge OUTPUT impedance (in your case 4 ohms.) However your preamp's PHONO SECTION INPUT IMPEDANCE should be equal to or higher than the transformer's OUTPUT impedance.

Your preamp's phono section has (I'm guessing) a default input impedance of 47K (for MM cartridges.) By inserting the 3.3K resistors, you are reducing the input impedance the transformer is looking at, which shunts some of it's power. I wouldn't use any additional resistors on the preamp side of the transformer. Doing so has no effect on the impedance the cartridge is looking at.

Some step-up transformers do provide for the use of cartridge loading resistors on the INPUT side of the transformer. I don't know if yours does.

I'm not sure what you mean by "quieter" with the resistors
in place.
Bryan, it's not wrong, but they're assuming you're going into a phono preamp meant for MC cartridges. And that you might want to adjust the output impedance of the transformer to fit a lower MC phono preamp input. This is not necessary when going into a 47K MM phonostage IMO.