I have a LM 518 powering Daedalus DA-RMa V2 speakers and have tried a range of preamps with it. TRL Dude, Tortuga LDR passive, Lampizator integrated passive, Vinnie Rossi AVC/LIO, and most recently iFi iTube2, LTA MZ2-S, Tubes4Hifi SP14, and Don Sachs Model 2.
First, I would say that it's always worth bypassing the volume pot and going with the direct line input. That integrated volume control on the 518 sucks the life out of the music - definitely a weak link. Second, I'm a fan of a well-designed tube preamp in front of the 518. It's a shame LM didn't design the direct line input to bypass the 12AX7 preamp stage, but even still, I find a nice tube preamp between source and the Line Magnetic to do wonders. My favorite of the above is what I currently own - the Don Sachs. For me, it gets the detail, tube dimensionality, tone, and meat on the bones, but also with a pace and rhythm that gives soul to the music. the LTA MZ2-S just didn't do the soul thing - though it was more detailed and open sounding. But the MZ2-S is a very nice and highly refined preamp, for sure. Just a different presentation style than the Don Sachs - up to one's tastes which one they'd prefer, IMO.
Finally, a friend owns the LM 218, which is basically the 518 without tube rectification or direct line input. He fronts it with a Shindo pre with internal phono pre as well. He has found the ideal Shindo VC setting at around 11am on the dial and leaves it there, then uses the 218's pot for VC. I love the sound of the Shindo/218 in his system - makes beautiful music. I just wonder how much better it could be if he didn't have to go through the 218's VC pot.
Also, I would say definitely upgrade those 845 tubes. I think the Psvane TII's are absolutely worth the $$ stretch - a warm and rich tonal sound with greatly improved refinement over the stock tubes. But if the rest of the system is up to it, the Psvane WE replica's are the real deal. If my current tubes fail sometime soon (hopefully not), I'd be interested in trying a couple of the new upper crust 845's that Shuguang and Psvane have released. The 518 absolutely can benefit from the top tubes out there, and not just in the 845 position.
First, I would say that it's always worth bypassing the volume pot and going with the direct line input. That integrated volume control on the 518 sucks the life out of the music - definitely a weak link. Second, I'm a fan of a well-designed tube preamp in front of the 518. It's a shame LM didn't design the direct line input to bypass the 12AX7 preamp stage, but even still, I find a nice tube preamp between source and the Line Magnetic to do wonders. My favorite of the above is what I currently own - the Don Sachs. For me, it gets the detail, tube dimensionality, tone, and meat on the bones, but also with a pace and rhythm that gives soul to the music. the LTA MZ2-S just didn't do the soul thing - though it was more detailed and open sounding. But the MZ2-S is a very nice and highly refined preamp, for sure. Just a different presentation style than the Don Sachs - up to one's tastes which one they'd prefer, IMO.
Finally, a friend owns the LM 218, which is basically the 518 without tube rectification or direct line input. He fronts it with a Shindo pre with internal phono pre as well. He has found the ideal Shindo VC setting at around 11am on the dial and leaves it there, then uses the 218's pot for VC. I love the sound of the Shindo/218 in his system - makes beautiful music. I just wonder how much better it could be if he didn't have to go through the 218's VC pot.
Also, I would say definitely upgrade those 845 tubes. I think the Psvane TII's are absolutely worth the $$ stretch - a warm and rich tonal sound with greatly improved refinement over the stock tubes. But if the rest of the system is up to it, the Psvane WE replica's are the real deal. If my current tubes fail sometime soon (hopefully not), I'd be interested in trying a couple of the new upper crust 845's that Shuguang and Psvane have released. The 518 absolutely can benefit from the top tubes out there, and not just in the 845 position.