Hi. I own a unit, and I would like to share my observations.
But first, I would like to say that I am not associated with any shop or group. I do not even personally know the WS-Tono guys, so I hope I am able to give unbiased opinions about the Violin.
My setup is as follows:
Usher CD-1 >> Tono Violin >> Adcom GFA535mkII >> Wharfe Diamond 9.6.
As for the 6sn7 tubes, I alternate between the stock Electro-Harmonix, and a pair of NOS Sylvania 6sn7w.
pros:
1. Increadible Gain. My amp is only 60wpc, but with the pre-amp gain at 9o'clock, it makes my floorstanders sing with gusto.
2. Responds well to 6sn7 tube rolling. Switching for the stock E-H to the Sylvanias, the hormonics that the Sylvania's are known for becomes very apparent.
3. Controlled an authoritative bass. Bass is not slow and sloppy at all.
4. Great treble extension. No extension was lost as compared to when I was running a pure SS setup.
cons:
1. The price. This may discourage some.
2. The stock EH 6sn7 is nothing to rave about. IMO, they sound very solid-state. Very analytical in nature, and lacks the 2nd-order harmonics that characterizes most tube setups.
3. There is a ~30 second hum though the speakers when I initially turn it on. I am not sure whether this is due to the tubes warming up, or due to pre-amp construction. But after that initial 30 seconds, the hum is gone.
So is it worth it?
For me, yes it is. Regardless of the price, its very much worth it because of the tube rolling capability, its like having many pre-amps in 1 unit. And again, it responds well to tube-rolling. This is probably the last pre-amp that I will ever own. Other than tube-rolling, the biggest Pro for me is probably the Gain, followed by the bass control. And by experience, good bass control is a sign of a robust power supply.
BUT, potential buyes who have pure SS setups should not expect a STOCK Violin to make damatic changes to their system. Well, you will immediaty notice the goo amount of Gain, but with the stock tubes, there is not much change in tonality. This is not the fault of the Violin; rather, its the Violin being transparent to the characteristics of the equiped tubes, with the stock E-H sounding very SS-like. Once you start tube-rolling, this is where the Violin (along with the newly-introduved tubes) really imparts its personality on the sound of your system. The only problem with tube rolling is that good 6sn7's are hard to find, and are not exactly cheap either.
Hope this helps.