I'm looking at a few phono preamp options in the next month or so. Budget is likely in the $400-500ish range, but the Musical Fidelity LX2 LPS seems to be a bargain at $200. It would match my M2Si amp as well, not that that matters. What I don't quite understand is the back panel, with RCA jacks for MC Load or MC input, and MM Load/MM input. What are the differences, which one are you supposed to use, or does it depend on your cartridge as well? Sorry if that seems like a dumb question, just not sure what this option is for, or how you use it.
The LX2-LPS has two inputs, one for MM and one for MC cartridges. Two different cartridges/turntables can be plugged in at once into the MM and MC Inputs. The MM section has a loading input for adding capacitance to better match some cartridges. The MC section has a loading input too, but for adding resistance. The LX2-LPS doesn’t have external dip switches for capacitance or resistance. It’s a good quality, but very basic unit. However, in the usual, thoughtful Musical Fidelity way, the designers added the loading inputs so that end users could still customize for various cartridges. The default settings of the LX2-LPS are very good though.
OK, thanks. So if you have just one TT, with say a MM cart, you would normally use the MM input. But if you are having issues with capacitance, long cables or what have you, you would use the MM Load input, am I correct on this then? And then the same would apply to the MC option as well. Front panel toggle, has you choose between MM or MC.
One other question, I see it can be powered via walwart with 12-24v range. Does it make a difference in tone to use the higher (or I guess lower) voltage?
With low output MC you must use MC, with high output MC you might be able to use both but there is a chance it might distort on MC input. The power adaptor voltage probably won't affect sound so much as the unit is likely to have a voltage controller inside but if you buy a higher quality power supply you might get better sound, not night and day but is likely to be noticeable.
I must add that is unlikely you have any serious audio problem with the standard set up as it comes from factory. They give you the choice to play with resistance and caps just to tailor it your taste.
If I understand what you are saying, then not exactly. For MM, you use the MM input, and if you need to load more capacitance, you can add loading plugs to the MM Load jacks. Your phono cable is still plugged into the MM input. Same with MC, you’re always plugging into the input, but using the MC Load jacks to add resistance with plugs. The load plugs just take the place of dip switches most adjustable phono stages use.
If you have issues with to high capacitance due to to long cables you can not fix that. It is no way to decrease that your long interconnects have added. You can only add more if you need..
Thanks again, yes - I think my confusion is the loading plugs, what exactly are these? I think I read something that it does not come with these plugs. I don't think I'll have any issue with capacitance, my cables are short, nothing exotic in my setup. Haven't decided on TT or cart, but leaning towards the Technics SL12000Mk7 and an AT VM540. I can get it premounted on a headshell, and plug and play to the SL.
I was under the impression it comes with at least some plugs when I was strongly considering either this or the almost identical LX-LPS, but I can’t confirm for sure what is included with it. Loading plugs for MM can only add capacitance, though, not subtract it. Likely with an AT cartridge, you would not be looking to add capacitance, anyway, and if you end up with a cartridge needing capacitance added, you can get/make/have made the necessary plugs at that time. Essentially the plugs just add capacitance to the circuit by plugging them in, as opposed to dip switches with switch various levels of capacitance in and out of the circuit. The plugs are a simpler design, IMO, though it is possible to add loading plugs to phono stages that don’t have jacks like this one does. To me, this design is not necessarily any more favorable than a design that lacks built-in loading options, but may be more dependable than a design that used dip switches (and this is probably overthinking things). If you move to MC using the LX2-LPS, then I would expect you might need plugs, but IMO that’s a bridge to cross if you ever come to it.
I suggest just forgetting about the loading plugs for now. Just play music for awhile and then play around with the plugs later if you want. I couldn’t tell a difference using them on my system. With a different setup or different ears you may hear a difference but I doubt that it will be night and day.
I had an older Musical Fidelity X-LPS that I used on my upgraded Rega RP6 with the Exact cart. I have to say, that the Musical Fidelity is a very nice sounding phono preamp. I don't think you can beat it for the current sale price. I listened to it up against a far more expensive tube preamp on my other turntable. Enjoy your LX2-LPS!
I'm sorry, but that is not correct. The "MM Load" is for resistance too, not capacitance. The LX2-LPS comes with a 47K ohm plug för the MM Load input. You have the option of changing the resistance for the MM input, this can be useful with some high output MC cartridges that needs to be run in the MM input (because of the gain). The LX2-LPS has a fixed capacitance of 100 pF for the MM input. This cannot be changed.
Yes, the LX was supplied with loading plugs. The LX2-LPS only comes with 47K (for MM) and 100 (for MC). No other plugs. For other plugs, one can contact the dealer.
Can I use a high-quality multimeter (Fluke 287) to probe the resistance and capacitance of all RCA ports? Actually, I've already tried this but I'm getting some unbelievable values. So there might be something inherently wrong with probing the ports with a multimeter. But how else would one do it? (Note: I do have the unit powered on during measurements - this especially affects the capacitance measurements.)
Thanks chili555, I must have tried for over an hour to post that image using imgur and others....strange! Any tips are most welcome. In the image, the smaller black-filled circles represent the center 'pin' of an RCA port, and the surrounding open circles represent the 'shield' of an RCA port. I hope that the rest of the image is self-explanatory. I purchased my LX2-LPS in Dec. 2019, and it did NOT come with loading plugs of any type. I confirmed that the Loading ports (both MC and MM Loading ports) are electrically tied in parallel internally to their respective Input ports (i.e., pin-to-pin, shield-to-shield). This means that adding resistors to the Loading ports (either MC or MM) can only reduce the total load resistance, while adding capacitors to the Loading ports (either MC or MM) can only increase the total load capacitance. If one so desires, you could add both resistors and capacitors simultaneously to a Loading port. I made resistance and capacitance measurements on all the ports using a state-of-the-art Fluke 287 multimeter (and another Fluke meter as well, just to confirm that the meter was not faulty), and the measured values do NOT agree with the specs that are advertised by Musical Fidelity, at least the very few specs that they advertise. The LX2-LPS was powered ON for these measurements – this made a difference to the measured capacitances vs. being powered off, but did not seem to affect the resistance measurements. MM Input port: Musical Fidelity advertises: 47 kOhm I measured: 120 kOhm, 80 uF (yes, MICRO farads) ….my MM cartridge, as with many MM's, expects to see a cap load of ~150 pF (PICO farads), but I can’t reduce the capacitance via the MM Loading ports (in this case, from 80 uF to 150 pF) – capacitance can only be increased. …if I placed a 77 kOhm plug into the Loading port the total loading resistance would be an 'ideal' 47 kOhms (via the parallel resistance formula). MC Input port: Musical Fidelity advertises: 100 Ohm I measured: 100 kOhm (yes, KILO ohms), 50 uF …most MC cartridges want ~100-500 Ohms, I’m not sure what capacitance an MC expects to see. If you placed a 100 Ohm plug into the Loading port the total loading resistance would be 99.9 Ohms. Output port: Musical Fidelity advertises: ‘nothing’ I measured: 20 kOhm (yes, KILO ohms), 200 uF …typical preamps have an output resistance of ~250 Ohms, so 20 kOhm is WAY too high. Concerning the above measurements, I triple-checked the values. I also measured various resistors and capacitors to make sure that the multimeter was working properly. I am at a loss to explain these measurements. Perhaps I should repeat these measurements on a different make of phono preamp....suggestions are most welcome!
I upgraded my Schiit Mani to the LX2-LPS and it did not come with loading plugs, like the LX does. So I am wondering how to go about getting them? Or what I need to make them?
Your multimeter is measuring DC resistance and not AC impedence. Music is not DC; it is AC. Electrical resistance and conductance - Wikipedia
The specified input and output for the LX2-LPS are - just like the specs for all other phone preamps - for circuit loads. All you’ve done is measure the electrical characteristics of the connectors and the grounding scheme used by Musical Fidelity, but even then the measurements are uncontrolled so you’re getting bizarre numbers. Such measurements are irrelevant because you’re not actually measuring the way in which the resistance, capacitance and gain in the preamp circuit circuit are loading the cartridge. To do that, you have to gain access to circuit board directly. That will void your warranty and, even when working with dummy loads, may damage your preamp.
Please help me understand why, then, the loading plugs should be populated (e.g., if making them yourself) with resistors and/or capacitors that are selected based on their DC properties? It would seem that the DC values (ohms and farads) as measured at the ports are at least somewhat meaningful. At one time apparently the LX2-LPS came with with a 47K ohm plug (for MM cartridges) and 100 ohm plug (for MC cartridges), as referenced in this post: Musical Fidelity - LX2 LPS Phono Preamp Question
A purely resistive load is measured in Ohms. It has no qualities of capacitance ot inductance. Because of this, its value is always the same whether in a DC circuit or an AC circuit. A capacitor is a device for storing electricity, it is measured in Farads. Because a Farad is a large number, they are most commonly specified in much smaller units, which are small fractions of a Farad. These values are constant for a capacitor, be it on a DC circuit or an AC circuit. You just can't stick a meter any where you want to in a circuit and expect to take any reading that would have any meaning at all. You have to know and understand what you are measuring. For example, you can't take a capacitor on a circuit board and measure its value with a meter thst measures capacitance, while it is still attached to the circuit board. It would have to be have to be removed from the other components on the board, in order to test it.
