Cartridge loading

This has been covered elsewhere but seems to need repetition.

Most Low Output Moving Coil cartridges are unaffected directly by the load, other than the output that have if the load value is too low. But we hear differences at times- so the load is making a difference in some cases.

Here is what is happening:

The cartridge has a small inductance, and the interconnect cable has a small capacitance. Together they form a Radio Frequency (RF) tuned circuit. The action of the cartridge provides the energy to 'excite' the tuned circuit- essentially the phono section is subjected to bursts of RF energy!

Now some phono sections don't care about this, if that is the case you will find the stock 47K to work fine. But if you find that the loading makes a difference and is critical, this is because the load value is reducing the 'Q' (Quality) of the RF tuned circuit, thus reducing the RF bursts. IOW the preamp is sensitive to RF!

If a cartridge manufacturer recommends a loading value, it almost always means that the phono section they use has this sensitivity. Further, it is indeed affected by the interconnect cable as Raul pointed out, so the actual loading value is variable. In short I would pay no attention to the recommendation from the manufacturer in this case.

Instead go with your ears. Try it with no loading first. Then try the highest setting offered by the preamp and work your way down. You will find out in short order whether your preamp is sensitive/has a problem with RF.

Atmasphere brought up a reason for having some loading with stages sensitive to RFI. I helped set up a table for someone with a Hovland preamp. We had problems with noise that turned out to be RFI. The factory "default" loading for the Hovland turned out to be 100k (essentially no loading). The unit had to be opened up to find this out and to make a change. Adding some loading cured the RFI problem.

A cartridge manufacturer, I believe Jonathan Carr of Lyra, mentioned another possible reason that loading might help. He noted that the response peak of modern cartridges are so high in frequency that loading should have minimal effect on audible frequency response. However, he speculated that some phonostages or linestages might be incapable of handling the signal level of the ultrasonic peak of cartridges, in which case, some loading might help in taming such peaks.

Oh horror! I use a 'blanco' record (without groove) for the
bias adjustment. Not to determine the bias force but to have any idea where to start. The same apply for the 10 x 'rule' . One needs some orientation 'point(s)' and can 'tune by ear' from there. Or so I thought.

Larryi, Jonathan Carr and I are talking about the same thing.

The 'ultrasonic' frequency can be in the MHz. Sometimes its easier to think of that as RF which is why I put it that way.