what's the rest of the system? Could it be that the BAT pre has too much gain for your amp? Look at all the specs of this preamp and compare them to the specs of the other pres you had. Something is not right. There could be some midrange bloom since it's a tube unit, but it shouldn't be as excessive as you describe.
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How many hours do you have on the tubes? It could be that they are still burning in.
That being said, I preffered the older VK-31SE/VK-51SE series to the newer VK-32SE that I auditioned, for similar reasons. I found the VK-32SE to have a sweeter midrange, with more bloom, but it lost much of the dynamics and authority of the VK-31SE/VK-51SE, IMHO. FWIW, I solved this problem by buying a ARC Ref 3, which I like better than all of the BAT preamps, though I'm still using a BAT amp.
How many hours do have on this unit? Most take 200 before sounding their best. Some interconnects can interact and cause anomalies as well. If this is a new unit- give it some time. You can burn it in by playing your CD (on repeat) through it with your power amp turned off. What did it sound like with the original tubes?
It is worth pointing out that Frontier1 is baselining against the excellent ASL Flora, which is not displaying the excessive bloom. This suggests that the issue may be specific to the VK52Se. Frontier1 already reported this bloom to me before replacing the SovTec 6H30PIds with the DR NOS Supertube variant.
'Thank you gentleman, your observations are quite astute. One radical suggestion has been to change the output coupling caps to teflon since oil caps can possess a certain forward sounding midrange. This, of course alters the intended sonic signature of the preamp. I'll continue to burn in the beast and see what gives. As stated in my post, this preamplifier has more air and top extension than several others I've had the opportunity to preview.
It seems BAT consider its pervasive use of oil capacitors a main feature of the VK 52SE. Design of 52SE may very well have been optimized for these caps. See:
I fear that replacing those oil caps with other technologies may yield unpredictable results. . . how about talking to BAT first about your concerns?
Rodman99999's suggestion makes sense. I'll give it another 2 weeks or so before making a decision on this BAT. As Guido notes, my frame of reference is an ASL Flora which is an excellent pre. From bottom to top it is very good indeed. As is the way with so many of us audio nuts, we're always looking for the next level of sonic perfection. My amps are a wonderful set of Audio Aero Prestige 40 wat monoblocks which will remain in the system indefinitely. They employ the GE211 and 813 as driver tubes, fantastic! As a point of interest, do oil filled caps take longer than for example Teflon to break in? Again, the many observations are a great help.
If you know what to listen for, and thrill to the sound of live music in a real venue: nothing beats tubes. Any equipment(tube or SS) takes time to sound it's best. Taking the time to burn in gear, and taste various tubes, is an act of love for some of us. Skydivers(I) have a saying: "We that dance are considered crazy by those that can't hear the music." Harley riders(I) have another: "If I have to explain- You wouldn't understand." Oil-filled caps will usually have somewhat of a fuller, rounder midrange(ala Mullard tubes, for instance- which some like), than would most film/foil caps(polypropylene/copper foil probably being the other extreme). I'm not certain about the burn-in time.
In my experience the BAT tube gear sounds very tubey and bloomy and that is what some listeners prefer about them. Also, BAT has for years offered the NOS variant tubes you are referring to as a desirable upgrade option.
My experience with those tubes suggests that they indeed may make the sound even more rich than the stock leaner sounding Sovetek 6H30's, pushing the already tubey house sound even further in that direction.
If you are looking for more neutral sound try an ARC or VTL piece instead. Otherwise returning to the Sovtek tubes will at least cause the sound to head in the other direction.
Tweeking equipment is not very difficult, and can yield outstanding results when applied to an already good piece of gear. I've used the MultiCap film and foil polystyrenes, and auriCAPs to excellent result(very transparent). Always buy in 2% matched pairs, watch the voltage ratings, and be certain to orient with the outer foil lead end toward the load(auriCAP leads are color coded). Again- I'd never recommend anything be changed until one knows beyond doubt the equipment's sound after burn-in. Often it just takes an interconnect/cable change to eliminate colorations.
While I agree that swapping out the oil caps is a bit extreme, and not something I would recommend or do (I would move on to another preamp, as Davemitchell suggests), I do know that quite a few have switched out the BAT coupling caps in the VK-75SE amplifier with Teflon VH caps, and have reported increased clarity and transparency. Some have even said that this cap change has more sonic benefits than changing tubes. Try contacting member Dgarretson, and/or search the archives.
Those teflon V-Caps do sound intriguing. AudioCap has teflon/tin foil caps as well. Same manufacturer as the MultiCaps I recommended. These caps are the creations of one Richard Marsh(the founder of Marsh Sound Design). If you know how good his electronics are: now you know part of the reason. One nice thing about tube gear- There aren't that many devices in the signal path(not really much to replace). Oh- the V-Caps take about 4 or 500 hrs to fully burn-in(so they say).
I have the BAT VKD5SE with SuperPak and the VK50SE. I have never found the BAT house sound to be "tubey". I think in many cases it can be a simple matter of tweaking power cords and cabling. The BAT tube gear has always provided me with a sense of air and presence that tubes do well, yet solid bass that is more like solid state.
In my experience, the power cord can often times take care of this type of "bloom". Sometimes too much of a good thing can lead to a bad thing and that may very well be the situation with your matching of components and cables. Since cables are rather inexpensive compared to components, I would recommend changing up some power cables or interconnects first. I have found the different Elrod power cables to be excellent for tubed front end gear. It would be good to know a little more about the entire setup including cabling to further look at the situation.