Musical Fidelity Phono preamp loading


I just bought a Musical Fidelity LX-LPS. They are cheap now and I was wanting to use it to experiment with cartridge loading. It comes with 5 different loading plugs that you put into rca jacks in the back. I think. Does anyone have experience with this unit? It comes with no information on how to use the supplied rca loading plugs. There are two black ones that are closed-back lugs. Instructions say the blue ringed ones are for typical MM carts, and the green ringed ones are for typical MC carts. That’s all the information on those. Then there are three sets of open backed rca lugs. The sheet says the white ones are 1K. Ohms I guess. The red ones are listed as 200 ohm. The yellow ones are 500 ohm. But these are open at the back and accept an rca plug. The circuit is not complete unless something gets plugged into them. Would the rca phono outputs get plugged into these? Or the black lugs?  So far the test MM and MC cartridges I’m using sound best without the black plugs inserted. They seem to attenuate output. That is my guess. I have no idea how to use the other lugs to see what they do.  I’ve contacted the manufacturer but they just said contact the dealer. I contacted music direct but not heard back. Given that this is the weekend I’m not expecting to hear from them. So if any of you can help I’d like to experiment with this unit this weekend. Maybe I’m the  only one on the planet that doesn’t just know how to use this thing, but I’m still surprised there is zero instructions with the unit. And no review or other online instructions I can find. Thanks for any tips on use. 
vinylfan62
Loading plugs: The standard values as supplied (Green plugs for MC, Blue plugs for MM) can be used for the majority of today’s cartridges or custom values can be fitted to match your preference.

These go into the "load" inputs.
Thanks. I have gotten that far. There are more loading plugs included. These are open at the back and don’t seem to be a complete circuit without something plugged into them. That’s the mystery. I won’t be buying any other Musical Fidelity products after contacting them and being told to see the dealer. Dealer has no documentation either. 
The open plugs are to make your own loading value.  Just use whatever plug is the closest to the manufacturer's recommended load value of the cartridge.
That makes more sense than other advice I’ve gotten so far on the open ended plugs. Thanks!
100Ω RCA Plugs (Green for MC loading)
47pF RCA Plugs (Blue for MM loading)

You can custom the loading plug using different value resistor/capacitor.

http://www.salonav.com/wp-content/uploads/2016/12/05-1.jpg

http://www.salonav.com/wp-content/uploads/2016/12/06-1.jpg
Thanks. I did figure out the black lugs with blue or green rings. It was the other three sets that I was unsure about how I would use them. I think I have it now. Amazing that a company would put this much thought into a product and then not document or support it. I have bought from the in the past, but I won’t be buying from Musical Fidelity again. 
All above correct. The dealers should have enough competence to have advised this to begin with. Though an oversight on the manual - wholly agreed. 

It came with 2 x 100 ohm RCA Plugs (Green for MC loading), and 2 x 47pF RCA Plugs (Blue for MM loading).

Another oversight from the Manual - the MC input impedance of  the LX2-LPS stated in manual is wrong, it should be approx 3.8K. This suits higher output cartridges, and am quite sure most if not all will sound fine with this “somewhat low impedance” loading.

The product was a pre takeover product, and I can assure you now that Audio Tuning are in charge support is a lot better, and there are new and exciting products in the pipeline. So please don't dismiss a brand based on an older product and poor support from a dealer ! The support network is a lot better now. If the dealer had contacted MF HQ they should have been given the above information
 


47k Ohm (not pF) 
I hope you are correct, Chak.  That was my thought as well.  It would seem that with no plug installed, there is no load resistance.  In other words, there is no permanently installed load resistor at all between the gate and ground of the input transistor in the phono section (assuming the unit is solid state).  Is that correct, for those of the responders who know something about this unit? 
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Well, if there is no permanent load resistance; if the user has total control via changing plugs, that is actually not a bad feature, so long as one knows about it and knows enough to use the feature properly.  (This is in contrast to almost every other phono stage I know about that uses plug-in resistors to alter load, where the added R is in parallel with some permanently installed resistance value, usually 47K ohms.  I think there is one other product where the permanent resistor is very high in value, like 1M.  That would work too. In that case, any plug in resistance is going to dominate.
47K is the standard input impedance for a phono section, MM or LOMC.


If this were mine I'd using a DVM and measure the resistance between the connections of the RCA jack and see what's there. I'd also use the DVM to see what the RCA plug thingys are as well.


You can't just use one value for MM cartridges; its variable depending on the cartridge and the tonearm interconnect cable! Take a look here:http://www.hagtech.com/loading.html

100 ohms isn't a standard either- when a load like that is specified, it suggests that the phono section is vulnerable to the RFI generated by the cartridge messes with the input of the phono section. See that link above.