ArthurOtt wrote:
Hello, I also own a BAT VK3i preamp but I don't have it in my system currently. I was actually thinking about selling it. It was recapped in 2019 with the stock Jensen 1uF 400 VDC caps. I see that you've done some mods on your VK3i in regard to the caps. Can you tell me more about what you've done and how it's changed the performance of the preamp? Thx......Arthur
I discussed the end result when I announced the discovery of the Russian Hybrid caps. As far as global upgrades are concerned -- the question is -- what didn't I do?
All of the power supply caps were replaced with industrial-grade products having a 105-degree C or better rating and designed for long life and low ESR.
The 1-ufd power-supply bypass caps were replaced with 20-ufd polycarbonate caps bypassed with .27-ufd CRC hermetic Teflon caps
The 1-Kohm grid-stop resistors were replaced with RN-65 Vishay bulk-film resistors. The input resistors were candidates but "buried" under the four volume control boards (disassembly is not recommended).
The Jensen output couplers were replaced with hermetic 2.2-ufd K75-24 Russian hybrid capacitors bypassed with .25-ufd Tex-Cap hermetic Teflon caps.
Output buffer resistors were added as the pre-amp was designed without any. ??? I installed Vishay RN-90 bulk-film resistors.
Past mods included shielding to limit RF contamination from the digital volume level controller. I also added 2-ufd capacitors across the filament supply to the 6V6 current sources
Tube complement is Eastern Block Amperex ECC88s and mil-spec RCA metal jacket 6V6s. Teflon damping rings were installed on the ECC88s and Pearl Coolers on the 6V6s.
Case work included extensive constrained layer damping where-ever possible using ceramic tiles and RTV silicone.
Since I am obsessive (no surprise there) I blinged-up the cosmetics.
Was all that WORK justified and worth it? DAMN RIGHT!!! I had no interest in any other pre-amps either new or used. For me -- this baby is a keeper!