Hi David,
I have a few inexpensive suggestions I'd like you to try, and please reply to this thread with your findings. There's no objective reason for an XV-1s to sound shut-in and undynamic on your rig.
1. Tracking Force:
Play with this first. It's something you can do at home and at little to no expense.
You will need a scale with .01 gram sensitivity. .1 gram will not do. Cartridges of this caliber will speak with a different voice, with as little as a .05 gram change, and the rounding error in a .1 gram sensitivity scale will not give you repeatable results.
Run the Dynavector and track it anywhere from 1.85 to 2.0 grams. IGNORE the advice about tracking at 2.5 grams. I have found in my personal cartridge (Schröder Reference and Triplanar tonearms on my turntables) has a sweet spot of about 1.87 grams. As I work my way to 1.92, the dynamics and pace suffer.
Comments you find referencing tracking the XV-1s at 2.5 on this forum and elsewhere are ill-informed, to put it kindly. In 5 different XV-1s based setups, the median tracking force has centered in on 1.90 grams.
The Dynavector importer agrees with me about this.
If you surf the archives, you will find numerous posts from both myself as well as Doug Deacon on the topic. In short, you want to track on the razor's edge ... the point slightly heavier than where you mis-track and NO MORE.
When you track at too heavy a force, not only will you lose dynamics, but the sense of pace will slow down. I kid you not.
2. Turntable Setup.
We all know about Linns and their sensitivity to suspension setup. I suggest you take your LP12 in for a suspension tune-up. The Dynavector, while extraordinarily dynamic is also very smooth. It may well be that what you had been previously perceiving as dynamics was more a system resonance or other "nasty". The revealing (and yet well behaved) nature of the Dynavector may be trying to tell you something.
If there is one sonic bias the Linn has, it's to present an "impression" of dynamics, so I'd definitely look into your setup.
3. Electronics and Loading.
Much as I'd love to sell you an Artemis phono stage, I'd like you to try to demo some other fine units too - including but not limited to the Hagerman Trumpet, Nick Doshi's Alap, and either an Art Audio or Kevin Carter's kit version of this phono stage, available through K&K audio. Kevin imports the Lundahl iron.
Yes, many of these units are not easily demoed, but an effort on your part to find some of them will be rewarded. Depending on where you live, I'm sure that members of this forum can help you out with this.
I strongly disagree with comments you read on this forum about the flaws inherent in step-up transformers, in spite of the high performance level set by some units which eschew them. This forum was recently polluted with several threads on this topic, so I won't go into that topic here. This is however another case of being able to achieve excellent results via many different architectures. It's all in the design and execution - not the architecture. Listen for results, and let the engineers argue it out.
While I would most certainly look into electronics first, the Lundahl transformers (LL 9206 from K&K Audio) are quite nice, and the Intact Audio custom wound trannies are extraordinary.
Your loading is in the ballpark for an XV-1s, which makes me think that there is more to your problem. I've seen XV-1s' loaded anywhere from 35 to 150 ohms, and certainly the higher side of the spectrum will favor dynamics rather than suppress them.
It is for this reason that your comment about favoring a reduction from 680 to 150 ohms puzzles me a bit. I fear you may be trying to address too many variables at once. It's easy to get lost.
I don't have experience with Cary's RIAA stages, but I have found that their power amps to tend toward a dark, shut-in sound and work well to compensate for aggressive speakers. Perhaps this design philosophy / aesthetic transfers to their RIAA stages? I don't know. Only a comparison in your system help you learn more about this.
As Sirspeedy points out, some tube swaps would be instructive.
My main point however is that you may well be working through come conflicting problems and hence, losing your baseline. You may be experiencing a loss of dynamics through your phono stage and hence you are dissatisfied as you load your XV-1s down to 150 (reducing dynamics). At the same time, the XV-1s is likely correctly telling you that 680 is too high. Herein lies your conflict.
Once you have addressed item #s 1 and 2, I'd look into demoing phono stages. This may point you toward an answer.
Cheers,
Thom @ Galibier
