Mark Levinson No 52 Preamp phono stage custom loading


The ML site has a download for HIFI news article, for the phono stage, it states:

"Custom input loads, should one be required, can be configured using internal solder-less connections by your dealer."

The ML user manual is not much help either:

"R Load: This setting offers a choice of resistive loading values for the Phono input:
• 47k ohms: The most commonly specified value for most phono cartridges.
• 3.3, 5.0, 7.7, 10, 33, 50, 77, 100, and 330 ohms
• Other: Enables the use of a custom-installed load. If you require a custom load to match your phono setup, contact your authorized Mark Levinson dealer for details"

Does anyone know about how the custom loading is done or has anyone done this? Sounds like jumpers or something, but I cannot find any info on how to accomplish this, thanks.
dnicol
I learned here last year, it takes some research to get it. Then, if like me, I forget what I learned.

Take it apart, look at it, see how they physically change, then: STOP!
research your cartridge, then change settings.

47K is for the majority of MM cartridges, it’s like PASS on a SUT if running a MM thru it.

The lower ohm settings are for various low output MC cartridges (LOMC), each having two important specs:

signal strength ( .. mV;) needs boosting (x factor)

internal resistance ( .. ohms) needs/becomes boosted (relative to x factor squared)
this is the trickiest part. result is what resistance is ’shown to’ the MM input.

the ’starting goal’ for ’shown impedance’ is: cartridge internal impedance multiplied by 10. then, up or down from there.

i.e. my AT33PTG/II has signal strength .3mV and internal resistance of 10 ohms.

I need an x factor high enough to get the signal high enough for my MM Phono input
and, I would like to have the impedance shown to the MM 47k input to be around 100 ohms.

x factor effects the impedance by a formula involving x-factor squared.

I better stop now, anyway, take it apart!




It dawned on me that I should be able to also set the load to the option of 47K, and then use loading plugs. Example 900 ohm resistor used on a loading plug (1 male RCA to dual female RCA) would give me ~900 ohm resistive load?
SS Hyperion. I want to be able to resistive load between 470 and 1000 ohms. Loading plugs using 47K stage setting would be easier maybe to find what I like. Then I would use the internal screw terminals (if they exist in the No 52).