Why continue with the combo when you have already arrived at the solution? Our hobby is about synergy and when we find it we hold onto it and maybe tweak a little here or there, so we don't loose the synergy that's taken so long to find. Synergy to me also means arriving at the sound you really want to listen to without being in any way dissatisfied.
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I agree with Larry. You've already answered your own question. Your current pairing is not good for you, and you've already demonstrated other pairings that make it better.
If it were me, I'd sell both the BAT and the McCormack, simply because you're not satisfied with the synergy there, and try something entirely different (such as a killer all-tube integrated, for instance).
Probably the main contributor to the problems you are hearing is that the output impedance of the BAT and the input impedance of the DNA-500 are not a good match.
Stereophile's measurements of the VK-51SE indicate a sharp rise in output impedance from 410 ohms across most of the audio band to 4700 ohms at 20Hz. That will result in a significant deep bass rolloff when driving the DNA-500's relatively low 10,000 ohm input impedance. Higher frequencies may also be affected, to the extent that the two impedances vary differently as a function of frequency.
I note, btw, that the input impedance of DNA-225 is far higher than that of the DNA-500, 100K instead of 10K. 100K is an excellent match for the BAT's output impedance.
Another factor might be that if overall gains and sensitivities in the system are such that you are using the BAT's volume control in the upper part of its range, that apparently causes its frequency response to deteriorate considerably. That occurs even when amplifier input impedance is high. See Figure 2 of the Stereophile measurements.
The only solution I can think of that does not involve changing or modifying components would be to add something like a Burson AB160XLR balanced buffer between the two components. That would resolve the impedance matching issue. That particular buffer also apparently provides up to 6db of gain, so you would be using the BAT's volume control at somewhat lower settings, thereby helping the second problem I mentioned, if it is a problem.
An additional thought: How are you hooking up the sub(s)? I don't know whether or not the two XLR output connectors for each channel that are apparently provided on the BAT are individually buffered, but I would guess that they are not. If that is the case, and if you are connecting a sub to one of those two sets of outputs, that will make the impedance mismatch I described even worse (by a considerable amount, if as is often the case the input impedance of the sub is not high).
If the sub(s) have speaker-level inputs, connecting them to the amplifier outputs would resolve that aspect of the problem, although the preamp-to-power amp mismatch would remain.
Larry, Michael you do pose a solid question and sound reasoning. While I did find synergy with certain pairing of my equipment, I'm searching for a solution that would allow satisfaction with all pieces I choose to pair at any given time. It's just one of those things and I do thank you for your input, but I couln't part with theses pieces, it's truly nice equipment. Al, thank you for the ' Burson ' suggestion. In having read somethings on it I think it's worth a try. My sub ( HSU UL-15 ) connection is XLR out from the BAT to XLR in at the sub, at 21' per XLR cable. I do have a Behringer DEQ 1246 (?) RTA/DAC/EQ that I was thinking about placing between the preamp and sub since it has provisions for subwoofer/s. I admit I'm not much in the way of calculating impedance curves and such, just one who loves this audio hobby to the last breath. Any ideas regarding the Behringer additions? I will continue reading about the Burson, and I'm pretty sure it will be added soon. Thank you all for your assistance, this is what makes this hobby a true joy, audio friends!!!!!!
I couldn't find an input impedance spec for the line-level inputs of the Hsu sub. But I would feel pretty certain that the Burson buffer would have no problems driving the combined input impedances of the DNA-500 and either the sub or the Behringer. You would need an xlr y-adapter, such as one of these, to drive the two components from the Burson.
If your Behringer model is the DEQ2496, which is indicated here as having a 22K input impedance on its analog inputs, or if it is another model that is similar in that respect, it cannot be driven by the BAT without significant deep bass rolloff, even if no power amp were connected. But again, that load in combination with the input impedance of the DNA-500 should be no problem for the Burson buffer, or for most other comparable devices.
James, here's some straight ahead advice for you, as you stated, "I'm searching for a solution that would allow satisfaction with all pieces I choose to pair at any given time. It's just one of those things and I do thank you for your input, but I couln't part with theses pieces, it's truly nice equipment."
Then expect continued disappointment. When a match doesn't work, it doesn't work, and any additional use of that match will result in diminished returns. Barring some problem with the equipment, there are poor matches in gear which will never yield optimum results.
Can things be improved? Sure; you can continue to try different cables including power cords, jack up the quality of the source with an upgrade DAC and a fine grade digital cable, and perhaps a speaker upgrade or roll tubes in the BAT. In the end you could spend a lot more time and money - and still get mediocre/unsatisfactory results, all for the sake of being stubborn. :)
A component match "mistake" is a mistake, whether we emotionally want to accept it or not. Maybe you bought these and do not want to take a loss on selling one, or they were in the family prior, or perhaps WFA (Wife Financial Acceptance) factors into things. Whatever reason, if your goal is the best sound then continuing to use that set is a hindrance to your satisfaction.
This certainly demonstrates that simply tossing together well known names does not ensure the sound will be to one's liking. It would truly be a shame if this occurred as a consequence of a recommendation and you spent a boatload of money. Tough lesson, but not fatal. There are many people here who learned the hard way, took their lumps and became smarter component shoppers over time.
BTW, don't think that you'll be sure to hit the jackpot sonically next time if you employ a "hit or miss" methodology. Random selection of gear is not nearly as likely to result in success as doing one's homework, i.e. making trips to hear gear, going to an audio show, discussing the sound of various equipment with owners and dealers, talking to the manufacturer if possible about recommended matches, and reading reviews (I am a reviewer).
Now, if you don't want to believe the bulk of this input, but want to be hard-headed about it, that's also just one of those things. The gear won't magically transform on its own; only a component change will cause that, as had been astutely presented previously. Putting together audio systems is a pretty good way of humbling a person, as those who think they're really sharp will find out quickly that just because we think we can assemble a killer sounding rig by our logic, reality often doesn't work that way.
If I've been too hard on you, my apologies. However, it appears like you're resisting admitting the combo was not to your liking and refusing to accept the implications (i.e. having to take a loss in selling a component, or having to return to square one in searching for another).
Once again, you said, "I'm searching for a solution that would allow satisfaction with all pieces I choose to pair at any given time." If you could find an elegant answer to that, you'd be a very wealthy man. I've got decades of experience in audiophilia and have built dozens and dozens of systems and can assure you that "solution" does not exist - unless you opt for putting up with what you deem inferior sound.
As passionate as anyone can be about the devices and components they amass, numbers simply do not lie. Primarily of these as Al said are the impedance matches between preamp and amp.
Very often I FEEL PEOPLE PLUG & PLAY THINGS TOGETHER AND are disappointed due to the mismatching of impedance in their system not the quality of the pieces being bought or brought in for audition.
One can spend whatever one wishes on really great stuff but it MUST mate up well numerically (impeadancewise) with the up or downstream component or its a waste of time and money regardless the heritage, design, quality, or reputation of the piece, as the results will be as you are now discovering.
If you look also at the NF amps, youll note they too have a quite low imp rating akin to the McCormack, and consequently why the NF preamp works well or weller, uh, better sheesh with the big Ss amp than does the BAT vk51.
Note too, the BAT amps, which we all know if one goes all in house there is built in sysnergy, have far greater input imp numbers than do the McCormacks. 100K vs. 10K. They didnt just pick any old input imp rating for their amps, did they?
Naturally, the BAT pre and BAT amps will work well together.. of course the NF pre and amps will work well together too but mixing them up is where youll find problems if the impedances arent optimized for one another.
So pursue the work around.. and add another gizmo into the signal path, and some more cabling or decide which unit you let go of or mate up differently. Currently it seems the NF pre and big Mac are one path the BAT pre and a Hmmm BAT amp?, might be another..Or an amp with likewise input imp numbers closer to those of the BAT amplifiers.. 100K which in BATland equals 50K per leg. 100K total balanced.
course, you could also run w/o sub, and that might help but Id not bet a lot on it.
Al explained all of this to me in likewise fashion but on different gear just recently . And it does all make sense on paper and in practice.
Which ever way very good luck to you.
It seems that you posted a question a few months ago (http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1297092536&openfrom&1&4#1) about the concern of impedances between the two units. Now you know the answer, not just from theory but also practice.
One of the posters on that thread suggested calling McCormack and asking them if the BAT would be an appropriate fit. If you did that, I'm just curious what they said and what kinds of preamps might be optimal fits for the DNA-500.
As others have said above, don't get hung up over making it work with the gear you have now. Move on, and evolve your system sonically.
My fellow music lovers, thank you all for the hard truths, great realities and lessons within the numbers that I have yet to formaulate as a second sense. But in time that too shall come to past. While the suggestion of more research, which I can only do to the best of my mere understanding thus far, is my best alternative, I do not have the luxury of hearing any gear due to my geographical location. Also while it is true that aditional gear ( as a bandaid ) may or may not get me closer to the musical nirvana I'd like to reach, I have decided to enrich my equipment list with matching pieces from the companies that I have already assembled my electronics ( pres & amps ). From what little exposure I've had to BAT, McCormack, and Nuforce, I've come to like what they offer when they're in their element. The sub while useful, is something I can delgate to home theather, and not miss much in what each of my speaker systems offer. But trust me when I say, not one bit of you alls time an input is in vain. I now have to do a little more in house component matching, which I'm truly excited about ( more toys/candy ) because in the end with this sound advice I'm now more on track than before. I did communicate with Steve about matching a VTL preamp with the DNA, which could be a future option, but I'll be scanning the Gon for a BAT amplifier to begin with, do feel free to contact me with reasonable offers. I have a sound track record here ( & Ebay ) as fast trouble free payment/purchases. Thanks everyone, I'm taking my lumps in stride, after all I'm fortunate and blessed in being bale to purchase something of the things that I like, an in that I am grateful for that aspect as well as all comments that I have read here. Hard truths can be good truths if applied in realistic truth I suppose, thank you all........