phono pre loading and gain question

I have a Motif mp-11 phono pre. Inside, through switches, the gain can be set between 40, 45, and 48 db. On the front is a knob selector for loading with positions: 70 ohm, 100, 150, 250, 470, 1k, 2k, 5k, 10k, 20k, and 47k. I have read most of the threads and am still confused about how low of an output mc I can use. This feeds into a Sonic Frontiers preamp with 20db gain. I don't want to get a step-up transformer if I don't need one...but I would like to try a Shelter cartridge out. Also, why would my phono pre have so many loading choices but so little maximum gain. One more thing...are step ups very prone to noise or hum. thanks
You'll be about 15-20db short on gain for a Shelter, with that setup. The loading choices are an entirely different matter than the gain amounts. The loadings are to properly provide the cartridge with the correct characteristics that it is meant to drive. The gain settings are to increase the output of the cartridge to a useable level for the preamp to accept. Both are important to get the best from the cartridge.

Step up devices are not inherently noisy, but some cheaper head amps might be. Transformers may have some rolloffs or bass problems if you don't get a good one. The key is to buy a quality one of whatever type you choose.
Thanks for the response...but if I use a step-up then I just leave the loading on my phono pre on 47k?
With a step up transformer, the phono section would be loaded at the 47k ohm setting, and the load for the cartridge would be set at the input of the transformer, at an amount about 1/2 what is suggested as the normal load for going direct in to the phono stage, unless there is some specific directions by the manufacturer of the cartridge that it should be loaded at "X" for direct input, and "Y" for transformer. Some cartridge spec sheets will specify the loadings for both direct input and transformer.

I use a Shelter 501 with a step up transformer, and find that it works very well at a transformer loading of 40 ohms.
Tom, how is that possible? He has 48db of gain in the phono preamp and 20db in the preamp for a total of 68db before the 18 to 30db of gain that the amp will have. At most he could be 7db short, but I would think that he could make it easy on this. Then again, I have never owned the Shelter.
Sorry to but in on Tom's possible answer, but without knowing the input sensitivity of Skeyebox's amp and the efficiency of his speakers and the size of his listening room and what average listening level Skeyebox personally prefers... Who can say that he will or won't have enough gain with his present set up???
Marty, I have the Shelter and I use a Cotter step-up with 20db gain, a phono stage with 46db gain, and a line stage with 20db gain. That adds up to 86db gain, prior to entering the amplifier. I think that I am running a little "hot" and could drop back to about 80db without compromising anything. But I think that cartridge really needs about 80+db total gain in the front end before going to the amp.

You can do with less, but then you have to crank the volume, and raise the noise floor with it. I have also found that when you try to run the Shelter with too little phono gain, it suffers dynamically and sounds lifeless. I tried going direct into the phono stage and eliminating the 20db gain of the Cotter, and found it totally unsuitable with only 66db total gain in the front end. It was "dead" sounding that way. I put the Cotter back inline, and it was great. No contest.
On the other hand, unless the amplifier input is very sensitive (like the Monarchy Audio SM-70) and the speakers are very efficient (maybe 95 dB/watt or better), TWL is probably correct that the 68 dB of overall preamplification would not provide adequate volume levels with the Shelter 501.
To add to Plato's point, I have 100db speakers and my amp only requires three-tenths of a volt input to reach max output.
Wow! I knew you would set me straight on this one. That seems like a truckload of gain but these things are so cartidge specific, that's why I pointed out that you owned one and I don't. My only experience with super low output cartridges is with the Ortofon MC-2000 which had a little under .2mv output. With solid state amplification, at 200 ohms it would work just fine at around 70-72db of gain. My Denon 103D seems to work fine in the high 60s. Thanks again.
Just to add more of my equipment. (and thanks for the help)I have a Sonic Frontiers Power 1 connected with balanced cables to the Sonic Frontiers Line 1 and all that goes into Infinity Overture 3s which have a sensitivity of 93-94db.
Any suggestions on a step-up? There is an Ortofon T-3000 for sale will that work with most lomc? Thanks
I never used a T-3000, so I have no personal experience with it. I have heard it is a very nice unit. Make sure it has the gain you want, and the loading selections you want.

Another choice that is good, is the EAR MC3 step up transformer.
I now use a phono stage with 45dB gain in MM configuration in conjunction with an internally wired Lundahl LL9206 step up transformer set at +20dB gain for MC. I have a Shelter 501 MkII pickup.

When I ran it through a passive linestage (no gain) and into a McCormack DNA-225, 30dB gain, I experienced very good performance, indeed. I tried this setup with and without the step up and found greater dynamics when using the additional 20db gain, As such, I can see where Tom feels that Skeyebox might be teetering on the edge with respect to gain and the Shelter. As a side note, I find that, in my system, the Shelter sounds much better on most recordings when loaded at 300ohm, as opposed to the 100ohm recommended by Shelter. For some reason, the sound is generally just a bit thin when loaded at 100ohm. Too dumb to know why, just know what I hear.

I have used the same phono stage running through a linestage with 14dB and, of course, have more than enough gain and, in fact, am thinking of dialing back a bit on the MC step up.
OK, I tried the gain calculator at Kab Acoustics and for a MC output of .2mv and a desired preamp output of .5 volt the calculator recommends 64db of gain. The problem with the whole game is that gain only tells you if you can drive your amp to clipping, not what the noise structure will be when you get there and not how badly you are compromising dynamics. A lot of this mess is very cartridge and stepup specific.
Well, my amp is very low power, maybe I don't have alot of gain there, so I need to get it earlier in the system. I don't have a gain spec on my amp. Heck, all I know is that is what it takes to sound good in my system.
Tom, my comments were made to point out how important noise structure is to the whole equation, not to call into question the veracity of your statement. You own the cartridge, as I said, I don't. I would always, always, defer to your expertise in this area. It is a fascinating area of discussion though. The calculator is just some mathematical game really and cannot substitiute for the real world experience that you, and other owners, have with a given setup. Now captured bearing versus unipivot, knife edge and oil bearing arms, that's where we can have a hearty and respectfull disagreement.
thanks again! As always...very helpful...and much appreciated!