Trying a BAT VK-P5 with a Step up Transformer


I'm going to crack open a VK-P5 next week, making sure all its 10 tubes are all ok. I recently bought a step up transformer to try with it.

The story below is my journey on why I went this way.

The VK-P5 sounds good, but I feel it can be better. It has mixed reviews. Some negative, mostly bland. But I know it sounds good. I want it to be great.

Mike Fremers review here was not complimentary - https://www.analogplanet.com/conten...-preamplifier-produces-luxurious-“velvet-fog”

He described it as "Produces A Luxurious, “Velvet Fog”, which I read as a backhanded remark.

He used a .2mV output Transfiguration Proteus with a 1 ohm impedance. To me, that may have been too weak for a preamp 50dB of gain. I believe tubes like to be driven. They dont shine just barely at cruising speed. Carts also shine the best when they are properly loaded. The VK-P5's lower load setting is 100 ohm.

I also found someone who had success with the VK-P5 using a K&K set up transformer. https://www.audioasylum.com/reviews/Accessory/K-K-Audio/MC-Step-up-transformer-kit/vinyl/391364.html

His impression - "the sound is fantastic (necessarily reflecting the contribution of the Dynavector Te Kaitora cartridge, of course). The bass, if anything, is even more extended than with the Clearaudio; and the mid-bass is "richer" and fuller, but no less well-defined. The Clearaudio's strength is in the midrange (try any acoustic piano record!), but this is ever-so slightly more present and palpable. There is a qualitative difference bewteen this and the MM playback, which is that the MM seems to emphasize the leading edge of transients, whereas the MC has more "sustain" in its playback."

I got a Rothwell MC-1 280 ohm set up transformer that produce 22 db gain to attach my Dynavector 20x2L that puts out 0.28mv. I am going to tone down the output of the phono pre from 50 db to 44 db using the internal pot to produce a total of 66db gain with the SUT.

VK-P5 will be set at 47k ohms and 150pf capacitance using a user capacitor slot in the pre. The MC-1 Special will end up giving my Dynavector a 282 ohm load, with a 0.2% db reduction in output. I expect the system to put out a total of 65-66db gain.

I used the math shown here - http://www.rothwellaudioproducts.co.uk/html/mc_step-up_transformers_explai.html

47kohms / 5ohm squared = 1880 ohms

5 ohms / (1880 ohms + 5 ohms) = 0.002db gain reduction

The Dynvector sounds great at 100 ohms. Its sound pretty good at 1000 ohms. I do not expect 280 ohms to be an issue.

Pretty excited to get this system running. 10 tube phono pre with 66db gain. I do not expect to be disappointed.

It'll take a couple weeks giving some free time.
peguinpower

Showing 3 responses by tablejockey

$1150 is a fair price.

My phonostage has 60db, and I was   about to try a .25mv. cart(AT ART9XA) I played it safe with a .4mv instead.

My phonostage is tubed as well. All tubed-rectified/active gain-no step up. Things get extra hissy in quiet passages when the volume knob gets cranked,so getting more juice out of the cart is paramount. Enjoy.





 
You can always send it back to BAT for a refresh if things ever get uninspiring. Being what it is, I can't see how that can happen.

Whoever bought  this was probably happy camper.  Seems like decent price. The current P12 is $13k!
https://www.musicdirect.com/phono-preamps/bat-vk-p10se-tube-phono-preamp-demo
Interesting results.

I once  took a Zesto Allaso for a test drive. Plugged into the MM input of my Fosgate .I was curious to hear the difference (if any) between passive and the active gain.

While I did appreciate a smidge more of quiet when blasting something, I had to concentrate to hear what type of difference in SQ there was. Very subtle level of overall reduction of "organic/real"(best way I can describe it) presentation? Maybe a cartridge specific thing. I didn't  have an exotic LOMC-just used a AT ART9 .5mv. 

Maybe a different story with another cart? Perhaps one of those real low ->.3mv, fancy builds?