Cartridge incompatibility, Soundsmith and Luxman

@audiojan You might want to take a look at this website

http://hagtech.com/loading

Since your cartridge is a low output, scroll down to where the low output calculator is.

I dropped the values of your cartridge (2.75mH) and input load (0.1KOhms or 100 Ohms) and it spits out a rolloff value of only about 5KHz. That might sound rolled off 🙂

So you either need a different cartridge or modify the input load to be something higher. I put in the the 470 Ohm value as recommended and the rolloff changes to 27KHz!

So I think we found the problem.

@atmasphere Greatly appreciate it! So at least I'm not going mad (although my wife would disagree with that statement...).

It seems that every other solution but to replace the cartridge has quite a bit of drawback... going to an SUT adds complexity and additional cost; modifying the Luxman limits my ability to use something different in the future; standalone phono preamp adds more cost, more cables, more complexity.

Easiest solution seems to be a different cartridge.

The fact that the sound seems rolled off in the treble to you suggested that the relatively high inductance of the cartridge, compared to that of a typical LOMC, is causing a loading issue, as Atma-sphere just showed us. This was mentioned in my previous analysis as a possibility. SS do recommend a higher than minimum load resistance, and now we have confirmatory evidence that this is to compensate for the inductance. But I repeat, all you have to do is open the chassis and change the phono load resistors to any value equal to or above 470 ohms. I believe it would be a mistake (or at least an unnecessary expense) to go to a SUT, but if you do, be sure to consult Peter Ledermann who made the cartridge and probably has a deep understanding of how to match a SUT to it. Of course, then you use the MM inputs. I don’t understand why changing the phono load resistors, the simplest solution imaginable, incurs any more of a limitation in the future than the 100-ohm resistors constitute in the here and now. Worst case scenario: you switch back to 100 ohms for some future hypothetical cartridge. There really is NO cartridge that requires a 100-ohm load, actually. A cartridge that works well with a 100 ohm load will also work well with a 470 ohm load, but the reverse is not the case, as you now know. Good luck.

Please note CHANGING the internal resistors does NOT inhibit you in the least from other cartridges in future; it is totally the way to go (assuming the simple  change works for this circuit).  If you go to 470, or 1000 Ohms, you can ALWAYS use an external metal short RCA Y adapter ($12) with two female/one male RCA and insert RCA plugs with resistors soldered inside. Parallel resistors will bring it down to what ever you  need in future.  (product of values divided by sum of values). We have seen this ONE load value in this model before, and it is very short sighted in my NSHO.  The proper way is to have 1000 -2000 internal and at LEAST some open RCA females jacks on the rear apron, allowing you to put loading plugs in at will. If someone who knows circuitry can verify this circuit allows the 100 ohm resistors to be changed, let him know.....OR send ME the schematic. That is the lowest cost way to make this unit flexible like almost all models of MC preamp designs. Our high gain MCP-2 phono preamp ($1199) has a variable control to go from 10 Ohms to 5K Ohms. Another option. 

Peter Ledermann/Soundsmith

Great post! Thanks.