First off, a big thanks to Alex for trusting the community enough to allow this great amplifier to make the rounds. Ok, on to the impressions!
tl;dr => The LLmkII has the juice to take control of the SR007mkI and make it sing.
I have spent a few hours listening to the LLmkII and I would have to say that I am quite impressed with it. It is a great looking amp and I feel that it has the power to unlock the full potential of the Stax OIImkI headphones. For the comparison, I listened to a few of my tried and true "test tracks" and then just started going through my music library.
I am not sure if it is expectation bias* or not but I have always felt that I could hear the slight bass hump around 50 hz for the OII and was bugged by the peak at 10khz. When I first got a chance to actually sit down and listen to the OIIs in a quiet setting, it was when I purchased them about a year ago alongside the SRM-323s. The speed and precision of the headphones was like I remembered from my meet impressions but the low bass seemed absent and there was a crowded sense to the upper treble. The treble seemed unnatural to me. It felt like there was too much information in the highest register which I attributed to the rising response approaching 10khz. The best I could describe it was that the treble emphasis led to an accentuation of every minute detail in the high frequencies giving the sound a little more brittleness.
Enter the LLmkII. The first thing I noticed right away was the bass. As I stated in my first impressions, it was simultaneously more present and pronounced and at the same time cleaner and more precise. Tracks that I normally would pull out the Paradox for in order to get a more impact and low end extension now rock just as hard on the Stax. The LL seemed to greatly lesson the issue I had with the OII through the 323, which is that even though the low bass frequency response is only 3-6db down, the 50hz hump would mask its presence and therefore, my ability to enjoy the music.
The second thing I noticed with the LLmkII was the treble. I actually found myself turning up the LL louder than I would the 323 because the uncomfortable upper treble didn't become a limiting factor. It felt like the "busyness" or congestion was lifted from the upper register.
The two ends of the frequency spectrum stood out the most from just a basic comparison. As I started to do a little more back and forth between the two amps comparing my test tracks I started to feel like the individual instruments and sounds had more body and depth on the LL.
The best way I could summarize was that the 323 sounded "thin" in comparison.
Unfortunately I do not have any other "uber" stax amps around for comparison so I can't really draw any conclusions on that front. That being said, I think the LLmkII passed the defacto "can it drive the OII?" Stax test with flying colors.
Notes from the listening session:
Diamonds on the Souls of Her Shoes - Paul Simon: Graceland
This has been my go to track for sometime now. I am very familiar with how it sounds and have heard it enough times on enough systems that it acts as a great reference for me on how a piece of gear sounds. On the LLmkII the vocal harmonies of LBM and Simon sounded alive and real. The rhythm section and drums had plenty of punch and the horns managed to not sound as processed as they can on some systems.
Man in the Mirror - Michael Jackson: Bad
This is another familiarity track. A big test for me is to listen as each layer is added and see if the sound becomes compressed. The LL managed to maintain a sense of spaciousness throughout the cresendo whereas on the 323s it coul be anti-climatic. Another simple test here is the bass. When the synth bass line comes in it is punchy and tight. The 323s did not provide the weight it needed and tended to mush up the presentation. Not so with the LL.
Queensryche - Operation Mindcrime
This is actually a new addition to my test tracks. This recording is not mastered very dynamically and can easily sound flat on a lot of playback systems. The usual "audiophile" frequency response of tilted treble and rolled off bass totally kills the recording. This was one of the albums that had me reaching for the Paradox and questioning the Stax investment. With the LLmkII, I actually prefer listening to this album on the OII now.
I am using a Metric Halo LIO=8 with balanced outputs => LLmkII, and single ended into the 323s.
* innerfidelity measurements
Edited by raif - 4/24/13 at 11:36pm