Lack of Bass from my BAT VK-5i Preamp...

Just a quick update after having lived with NOS tubes in my BAT VK5iSE for a month. I am now using a matched pair of Amperex 7308 PQ's, and a matched pair of Tungsol 5881. This is an absolute "no brainer" upgrade, worth way more than the $ 200 or so I spent on tubes. A huge imptovement in soundstage width and depth, lower noise floor, superb placement of instruments and vocalists in the soundstage, a motr "present" midrange, more extended highs, more natural bass articulation, etc, etc, etc. To all BAT preamp owners, this is certainly worth a shot. In my limited tue rolling, I also tried a pair of Amperex 6DJ8 Holland Orange Globe logo. Nice, with a warmer, more prominent midrange, but less extended top and bottom than the 7308's. However, depedning on your asociated components, these can also work (still beat the stock tubes IMHO). Other things that HAVE Ssurprised me..the effect of power cords after I put the NOS tubes in. Hearing the difference between different cords is now VERY easy. The BMI Eel is still the champ for the buck, with an very romantic, engaging sound. An Audio Tekne cord gives up a lot of richness in the midrange to the Eel, but is perhaps (in this unit, with my associated components) more evenly balanced top to bottom and does a better job of "illuminating" the further reaches of the soundstage. Finally, the CPC Top Gun seemed to recover a good deal of the richness of the Eel, w/o giving up much (if any) of the detail of the Audio Tekne. All good, and no clue which is "right" - this is just to illustrate the higher level of refinement to which NOS tubes take an already great preamp....just wish I had a Whale and an Top Gun HCFI in the right lenght!

One of my friends once bought BAT VK-60 amp with VTL preamp(do not remember a precise model) No matter of impedance values on both ends which were good enough to match, he had the same problem as you do. He was advised to go onto BAT completely meaning having BAT source, preamp etc...
He did buy BAT VK5i and CD-player and than phono and he isn't complaining. He said to me that once you buy a single component of BAT, you'll have to eventually get a BAT complete system meaning that BAT can work with BAT. Does maybe anyone know if there is any problem with connecting BAT with non-BAT components? If you're about to answer than find my thread on amps-preamps forums to share some thoughts.

Might be just a characteristic of tubes to some extent. I have experimented with the following tube vs ss preamps and my results were similar to yours.

Adcom GFP-750 SS Preamp
CJ PV-14L tube preamp
CJ PV-12 tube preamp
Audio Research LS16 tube preamp

Other gear: CJ Premier 11a tube amp. Thiel CS 1.5 speakers. Cary 306/200 CD player.

Adcom: Had the the best frequency range with low, tight, and fast bass and higher treble extension than any of the tube preamps I've compared. Not quite the air, soundstage, or transparency of the tube preamps.

CJ PV-14L: The sweetest sounding of the preamps listed here but seemed to roll off the lows and highs a bit more than I liked in my system. Might be a nice match for a somewhat dry or sterile sounding system.

CJ PV-12: Similar to PV-14L above.

A.R. LS16: Broader frequency response vs CJ, a bit better bass with punch, faster transients, better treble. Not as sweet as CJ. Doesn't sound as "tubie" as CJ. Not quite the low end punch or high frequency extension as the Adcom GFP-750 but still retains some of that tube magic missing in the Adcom.

I mostly use my A.R. LS16 but still own the Adcom GFP-750. For me in my system, A.R. LS16 has the best sound. Best value would go to Adcom GFP-750.

Set the Amps input impedance to 20k ohms.