Helikon LOADING

Jeff: Well, yes, you are endeavoring to impedance-match the cartridge to the phono preamp. The 25x value may turn out to be right on the nose (after experimenting a little up or down and making listening comparisons, taking notes -- always take notes!)

But if it isn't right on the nose, the 25x value will still be pretty close, thus saving you a lot of time.

If you're using a MC cartridge with a typical output and coil resistance of +/_ 10 ohms (optimum loading around +/_ 250 ohms) you could also follow another approach which would take about the same amount of time. And that would be to start at the low end of value range (i.e. optimum less 50%) and work your way up in increments of say 25 ohms. In this example, 125, 150, 175, 200, etc.

I've done it this way too, and it may actually work better (in terms of training one's hearing) for someone who has never done it. You are guaranteed to start with sloppy bass which slowly tightens up and (if you keep going) eventually gets very thin, or disappears. That's when you back down 25 or 50 ohms and can be confident you've found the best match.

Years ago, all Lyra's were made for 47k, but only a few Phono Stages made that, so the manual changed the loading recommendations. I think, it is System dependent, too. When you have an adjustable one, you can check it out, from from setting you will loose high frequency information. I use most of the time 47k with a Klyne Phono Stage and it's own Filter settings, but there is not only 1 right value I guess.

Nsgarch - Good stuff, thanks! I started out out of phase with you on terminology.

Nsgarch- I thank you for the guidelines you have provided, that would sure help out me and other in simialr situations. May be I missed it but what was the rational behind the 25 times internal impedance rule? In any case the 25 time rule has been proving itself in my set up.

Nil, the 25x rule emerged from experience and experiment and also compiling data from those (few) cartridge manufacturers who actually publish optimum load values for their products (like van den Hul).

Anyway after compiling a lot of data (on normal output MC cartridges that is) and comparing it with various internal resistance figures, the multiple always seemed to come out at or near 25. To save time, since most cartridge maker's load specs are so vague, it seemed like starting with a value around 25X the internal resistance would put you at or very near the goal; instead of stabbing all over the place from 5 to 47K ohms!