Rega RP10 VTA shims

Hi Theo: I seem to have overlooked this question from you:

>On the demag or degaussing concern, what is your thought on the method of shorting the leads by touching the RCA connectors?

Shorting the cartridge while playing limits the amount of current pushed through the coils to whatever the cartridge can generate on its own. Ergo, it is the most gentle method of fluxbusting, and most likely can be used without qualms even on cartridges with magnets that are not so resistant to demagnetization (Alnico).

>I would like your direction on this before I risk ruining a perfectly good cartridge.

The present Lyra cartridges all use super-strong Neodymium 50 magnets (their powerful magnetic field is why metal particles from the turntable environment accumulate in the coil vicinity). In order to demagnetize these magnets, you would need to push so much current through the cartridge coils that they would vaporize first. Ergo, even if you use an active fluxbusting device, as long as the fluxbusting circuit is in proper working order, I don't believe that any of our present cartridges would suffer negative effects.

FWIW, an EE friend in Japan has built a re-magnetizing machine for MC cartridges. He reports that when used with Alnico-based MC cartridges from the 1960s and 1970s, the cartridge output voltage increased, indicating that magnet strength went up.

The later Alnico magnet formulas were engineered to better resist demagnetization, and should therefore benefit less from remagnetization. The rare-earth magnets (samarium cobalt, neodymium and whatnot) are inherently quite resistant to demagnetization, and probably would not benefit from remagnetization (although I doubt if remagnetization would hurt anything).

kind regards, jonathan

Mr. Carr, thank you for looking back at previous posts and responding to my question. I have read your response a couple times and must admit it is a little over my head. But if I understand your statements correctly, I could use a fluxbusting device, I should have favorable results. Any suggestions as to a brand or model with which you have had favorable results?
Thank you again for responding.
Theo

Thanks for the response, Jonathan. The Delos was really dialled in with a 3mm shim on my RP40/RB303 (and a 2mm Herbies Way Excellent Mat), but on the RP10/RB2000 it seems be doing well with a 1mm shim (and a 1.6mm Herbies Grungebuster mat).

I suspect that the RB2000 tonearm has a slightly higher pivot point (+2mm) then the RB303 tonearm.

On my Rega P9 with RB1000 arm I use 2 - 2mm spacers and a Herbie's Grungbuster mat for the P9. This was setup by my dealer.

Hi Theo: Fluxbusters can be divided into two types. The first type involve shorting the cartridge output into itself while playing, and therefore the amount of current pushed through the cartridge coils is limited to whatever the cartridge can produce by itself. This means that the fluxbusting process is completely safe for the cartridge, but the effectiveness of the fluxbusting process is limited.

The second type uses an active (powered) fluxbusting device (combining a sine wave signal source and power output stage) to forcibly inject current through the cartridge coils. Since the active fluxbusting device can force far more current through the cartridge coils than the cartridge can produce on its own, the effectiveness of the fluxbusting procedure is enhanced. However, since more current is forced through the cartridge coils than normal, there are those who fear that the current may reach dangerous levels for the coils, or may weaken the magnets that create the field that the coils operate in.

As long as the active fluxbuster designer did his job properly, the fluxbuster should be current-limited to not exceed a level that remains safe for most MC cartridges made (the finest wire used in cartridge production is 12 micrometers - smaller than that and the production failure rate becomes too high).

If any problems occur with an external fluxbuster, it will be when it is used in an application that falls outside of what the fluxbuster designer envisioned.

One such possibility would be when using MC cartridges that were built with early types of Alnico magnets (during the 1950s, 1960s, and possibly the early 1970s), that did not retain their magnetic strength very well. With these cartridges it may be safer to use passive fluxbusting (unless you have access to a magnet recharging service).

A second possibility would be when using MC cartridges with IC or printed-circuit (photo-etched) coils, as the resulting coils will have far smaller conducting cross-sections than any normal wire. Examples of such cartridges would include Yamaha's MC-1s and MC-1X, JVC's MC-1, MC-2E, MC-L10, and MC-1000. With these cartridges, again it may be safer to use passive fluxbusting.

A third possibility would be when the active fluxbuster has failing internal components. If you purchase an active fluxbuster second-hand or NOS, I strongly suggest that you test it out on a broken cartridge first before your prized reference MC!

Everyone should keep around at least one borked Denon DL-103 (which uses 14-micrometer wire in the coils).

>Any suggestions as to a brand or model with which you have had favorable results?

I don't think that too many models are available today, and I don't have any experience with any of them. I'd suggest going with a reputable brand - for example, Aesthetix's Benz ABCD-1 MC Cartridge Demagnetizer.

I hope that the above answered your questions and cleared up any opaque areas. If you have any more questions, please feel free to ask.

kind regards, jonathan carr