Audio research 16II or Pass X1

I'm trying to decide between these two pre's. Thanks to the help from some fellow A'goners, I've decided that if I decide to go the solid state route, I'll get a Pass. For the last week or so it's looked like I would go with a Pass. But now I've got this nagging feeling about a tubed Pre. I've heard good things about Audio Research. I had a chance to demo one about 10 years ago when I first got into Hi Fi and separate components. I know that without spending a small fortune, I have to make compromises. Tubes lack the last word in bass resolution and extension to the frequency extremes. On the other hand, I heard that SS, even the Pass does project a holographic image. So it's bass vs the ulitmate in imaging. Also, there's the midrange bloom people talk so much about. Not sure on that one. I've heard it and it's very seductive, but is it real or just another distortion. I'm not set on the AR 16II either, it just appears to have the quality and price I think I can live with. Other older AR pre's tend to be more "tooby." This, I think is the wrong direction for me. Undoubtedly my dilemma has been faced by many fellow audiophiles in the past. If anyone out there with patience and a kind heart would care to weigh in I sure appreciate it. Thanks.
The ARC LS 16 is extremely accurate at both frequency extremes and is hardly tubey sounding at all. It's a very neutral and accurate piece with excellent detail retrieval. It's just plain hard to fault. I bought mine and then looked to see what other people or reviewers had to say. The preamp isn't tubey enough for most toobofiles though and may be just what you are looking for. You'll be pleased. Just perfectly smooth and accurate. Do some research on the net and I believe you'll find it fits what you're looking for.
Before deciding, first check out the tiny power supply on the LS-16. The transformer is so small, I believe it is mounted directly on the circuit board. I own an ARC amp. But I am amazed at how cheap ARC is in what they give you in their preamps. I believe the unit weighs 11 pds. You might also read the reviews on of the LS 15, 16, & 22. There were several people who remarked on how small the power supplies are in the 15 and 16. Also, there was a comment about the bass and how the LS15 or 16 is unable to handle big dynamic swings, etc.

The Pass has a huge separate power supply. I have listened to it, and it is a very good sounding unit that is hard to fault. However, I believe tubes still have a little more midrange palpability, although the Pass fleshes out the sound in a 3-D fashion and with a body that is closest to tubes that I have heard, and certainly more than most transistor pieces can dream of doing.

Perhaps you should check out some other tube units such as BAT, CJ, Supratek.
As I am one of those who have commented on the LS 16 MK II in concerning power supply limitations and the effect in terms of dynamic bass swings, I thought I should add a few comments here. The transformer is not attached to the circuit-board; it is bolted on to the side of the unit, but there is a captive circuit board that takes the outputs from the transformer. I believe that it is a 35 VA transformer, compared with a 45 VA unit in the LS 25, and a 50 watt toroidal in the SP9 (any version).

The size of the transformer reflects cost compromises, but also the priority that Audio Research puts on transformer size. The capacitors in the unit are described by Audio Research as "expensive" or "costly" or words to that effect, and cost savings at that end could have purchased a larger transformer.

In order to get the best sound out of the unit, there should be a good sound conditioner used. This improves bass impact; eliminates an infrequent stressed quality to the midrange; and results in a blacker background. The unit is VERY sensitive in this regard, but so too is my SP 9 MK III, which has a large toroidal transformer (and which I still use as a phono premap). I use the unit with the Monster 5000 sound conditioner, classe cable, and at its IEC input, the last version of the VESA block sound filter. Removing any of these from the chain reduces bass impact, dynamics in the context of heavy bass recordings (CD not LP, and not very many CDs), and results in a less black background, or one might say, a lesser sense of ease. The sensitivity to line conditions is, I suspect, in part a function of the limitations on its power supply regulation: a smaller transformer results in higher power supply impedance, whatever one might say about the quality of the regulation circuitry that follows it. Having said that, I suspect that most preamps would benefit from a cleaned up power line, although probably not to the same extent.

I use the unit with the Audio Research VT 100 MK II, and as a line section is sounds MUCH better than the line section in the SP9 MK III (as it should, for the cost). Also, it sounds substantially better using its balanced outputs when driving the Audio Research VT 100 MK II (with the MK III there is said to be virtually no difference between the sound from the balanced and the SE inputs).

I hope this helps.