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.