[HiFiSoundGuy]

 Do they do anything or not? http://www.pacificvalve.us/YaqinTB.html ... http://www.epinions.com/content_312424107652

[Tweaker]

I have one. I found that it really doesn't do much except roll off the highs ever so slightly. I ddn't hear it add any "tube sound", it's really pretty neutral sounding. It's said  that with a good aftermarket power cord and the right tube (one of the Jan Philips, I think), that it can make an improvement. I've not tried either, yet. I have mine driving my subwoofer which did make an improvement in the systems sound. Relieving the preamp from the burden of having to drive a long set of sub woofer cables is why, I'm guessing.

[woodsyi]

They make any source component "world reference" class especially when you damp the tubes with concrete sealers. 

[doug s.]

i never tried one, but over on the head-fi forum a coupla folks have said they're better than the more expensive musical fidelity tube buffer, w/the aforementioned power cord & tube upgrade.

i have a couple tube buffers - two slightly modded ase z-man tube buffers, & a kailin tube buffer.  i have used them to good effect between tuner & preamp, between dac & preamp.  i am presently using one between deqx & amp in my system, on the hi-pass side..

doug s.

[K.C.]

Yes they do something. What depends on the tube and the source, not so much the AC cord in my experience.

I have both the original MF X10D and the V3. The original is fun because you can roll tubes and find a sound you like. I've got some Mullards in mine that sound warm and wonderful. The V3 on the other hand is very neutral and very nice for digital sources.