I am currently using a Grado Reference cartridge (4.5 mV output) with a Lehmann Audio Black Cube SE (which was the original version before I did the SE upgrade). The cartridge loading I use is 47 kOhms, with a 40 db gain setting (the setting specified for moving magnet cartridges). Since the Grado cartridges are moving-iron designs, which are somewhat less affected by the loading than true moving magnet designs, I think you should experiment with different impedance settings and see if one of them is more pleasing to you.
Can you clarify your the following points?:
1. Why do you think the cartridge/phono preamp "should sound better"? What aspects of the sound are you dissatisfied with?
2. What turntable / tonearm combo are you using? It's my experience that the TT/tonearm combo is as important as the cartridge you are using, so this is an important part of the equation.
The rest of your system is certainly first-rate, so it strikes me that you may be feeling dissatisfied because the Grado Platinum cartridge / Lehmann Black Cube aren't in the same league as the rest of your components, which are quite revealing of deficiencies in the upstream components.
As a first step, I strongly suggest that you upgrade your Lehmann Audio Black Cube to the "SE" version. The "SE" version offers a noticeable performance improvement over the original version, and the upgrade is not expensive (about $275, as I recall). When I upgraded my Black Cube, I was very pleased with the improved sound quality: much better bass response, a more transparent mid-range and treble, and somewhat better soundstaging (which was already pretty good).
If you are still vaguely dissatisfied with the sound of your analog front end, then you should consider getting a better cartridge. The Absolute Sound lists a number of cartridges in the $500-750 range that are worthy of audition, but one caveat: if you decide to buy a moving coil cartridge, you may find that the Lehmann Black Cube will also need replacement. Several audio reviewers (such as Michael Fremer) have written that the Black Cube is more "simpatico" with moving magnet cartridges than with moving coil units. I have no personal experience with this, so I only pass the remark along for what it's worth.
Can you clarify your the following points?:
1. Why do you think the cartridge/phono preamp "should sound better"? What aspects of the sound are you dissatisfied with?
2. What turntable / tonearm combo are you using? It's my experience that the TT/tonearm combo is as important as the cartridge you are using, so this is an important part of the equation.
The rest of your system is certainly first-rate, so it strikes me that you may be feeling dissatisfied because the Grado Platinum cartridge / Lehmann Black Cube aren't in the same league as the rest of your components, which are quite revealing of deficiencies in the upstream components.
As a first step, I strongly suggest that you upgrade your Lehmann Audio Black Cube to the "SE" version. The "SE" version offers a noticeable performance improvement over the original version, and the upgrade is not expensive (about $275, as I recall). When I upgraded my Black Cube, I was very pleased with the improved sound quality: much better bass response, a more transparent mid-range and treble, and somewhat better soundstaging (which was already pretty good).
If you are still vaguely dissatisfied with the sound of your analog front end, then you should consider getting a better cartridge. The Absolute Sound lists a number of cartridges in the $500-750 range that are worthy of audition, but one caveat: if you decide to buy a moving coil cartridge, you may find that the Lehmann Black Cube will also need replacement. Several audio reviewers (such as Michael Fremer) have written that the Black Cube is more "simpatico" with moving magnet cartridges than with moving coil units. I have no personal experience with this, so I only pass the remark along for what it's worth.