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

Dear Ted,

Could be an impedance mis-match. If the output impedance of the BAT is above 100 ohms and the input impedance of the Rowland is below 47 k ohms, then this mis-match alone could be causing all yr problems. The lower the actual impedance of the amp's inputs and the longer your interconnects between them, the worse this might sound. Please check yr manuals or call the factories to get the specs.

Best of luck,
Joe

Thanks a lot Joeabrams!! I did some research on specification of both pieces and found the following number:

BAT VK-5i:
- Minimum Power Amp Input Impedance = 10k Ohms each phase

Jeff Rowland Model 5 amp:
- Input Impedance is selectable to 100K,20K, and 600 Ohms
- Overall gain is also selectable to 20, 26, 29.5, 32 dB

Then I decided to do the research a little bit further for input impedance for BAT VK-60 amp which I believe its imput impedance should perfectly match with my VK-5i. It comes up with 200k Ohms each phase.

From those figures, I assume that setting JR5 to 100k Ohms would be the closer match to VK-5i, right?

Now if anybody know how the "overall gain" on my JR5 should be set, please explain to me.

Thanks for reading. Ted

Ted this is an FAQ of interest to many users, so I'd like to elaborate a bit on Joe's comments; perhaps you've slightly misunderstood. The ratio of interest here is the preamp's OUTPUT impedance vs. the power amp's input Z (Z = impedance). The P.A.'s input Z should be at least 10 times the pre's output Z. So if you select 100k-ohms input Z, the pre's output Z must be 10k-ohms (or less) to avoid lo or hi frequency (capacitive or inductive) frequency rolloff within your interconnects.
The BAT website does not offer spec's for the 5i, but looking at other models they do show the highest output Z of their line (the model 3i) output Z = 1k-ohm; other models are even lower (better). So your 5i's output Z is probably not the issue here.
Regarding gain, for best noise performance use the least amount of gain that you can, while still attaining full output drive capability (can you drive it into clip, or at least as loud as you desire to?). Try strapping for minimum gain & then work up from there if that's not adequate.
I am thinking that you may need to experiment with upgrade AC cords on the preamp, until you find one that gives you the tonality charactaristics that you prefer. Tube rolling, as you refer to, is of course another avenue of approach to attaining your desired charactaristics. This can also be combined with your AC cord tuning.
Finally you may need to experiment with component shelving, & or cones, & or vibrapods (isolation & vibration treatments). Like upgrade AC cords & tube rolling, this is an entire area of speciality unto itself & I am not going to attempt detailed explanations here.
Please use the forum search engine to locate the multitudes of detailed posts regarding all of the aforementioned techniques. There are many available tools at your disposal. Your choices of components above are very good; I suspect that you'll be easily able to achieve the desired results when you find which techniques work best, via experimentation, which is the only way to find out. There are no specific rules to doing this.

Although you are probably using good power cords, racks, footers, etc. I'll tell you what has made a difference w/ my BAT VK5i SE. Replacing the stock cord with a BMI EEL improved (at least perceptibly) bass extension and tightness. Putting the BAT on a Mana Pahse Four rack REALLY extended the bass (again, perceptibly). Finally, putting the unit on a Rollerblock "sandwich" (see recent issue of Listener) put the sound in a totally different league in terms on soundstage height, width, depth, backgrond noise and dynamic range. Haven tried any cords beyonf the EEL, but there are probably better ones (like the BMI Whale) out there. I will be putting NOS Tungsols 5881 and Amperex 7308 PQ tubes next weekend, so stay tuned for more..or drop me a private e-mail. By way of disclaimer, please note I use powered sub-woofer to cover the bottom end below 40 Hz, which does help matters, but the overall qualitative improvements of these tweak apply regardless. You may also want to look into a Neuance shelf - I believe Ken is now making a model that will support the VK5..and I plan to buy one in due time to replace the stock Mana glass sehlf (the Neuance worked wonders under my LP12)

I just got new tubes today and already put the Tungsol 5881 and Amperex 6DJ8 Orange Globe (Holland) into my BAT 5i tonight and it did sound much more convincing with more bass attack. By the way, I didn't have a chance to compare with my EAD Signature at this time. I'll post the comparison later.

Thanks everybody for you contribution.

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.