DAC to preamp technical question

Thanks for the responses fellas . A new twist in my journey . I had just purchased the BAT used from a hifi dealer in town last week . I inquired if they knew the tube life on the tubes . They did not know . So yesterday after about an hour of listening the left channel just went dead and gone . No warning signs what so ever .Shut her down , left and came back an hour later and started up again . This time it only took ten minutes for the same thing to happen again . I am assuming the tubes are in need of replacement . Might have some correlation as to why the BAT sounded worse with the higher sensitivity speakers ? Goerge , you really need to get over your obsession with putting down Hypex . LOL

I am a little confused with the determination of the BAT pre having a serious design flaw . Should it's cd input not be able to handle a standard 2 volts ? Or am I misunderstanding what I read here ? if so what would be a good match volt wise ? Also i am using the supplied balance to rca jacks that BAT recommends and claims has no derogatory influence on the sound . I do have three dacs coming later in the week . Two of them have  balanced outs , so I will be giving those a try as well .

Maplegrovemusic, no one is suggesting that the BAT has a design flaw.  Based on your latest posts, it appears that there are two separate issues:

1)A defect in your particular unit, which seems likely to account for the distortion that I had indicated earlier I was unable to explain.

2)Gain that is higher than desirable when used in conjunction with most digital sources, given also that amplifier and speaker sensitivities are average or higher.  I would expect, in the absence of defects in your particular unit, that the BAT could "handle" maximum inputs of 2 volts or more, but the consequence of its high gain would simply be having to operate the volume control in the lower part of its range.  That is a very common problem these days, when digital sources are used, and some well regarded preamps (such as many Conrad Johnson models) have gains that are even a good deal higher than the gain of your BAT.

That is the main reason that Rothwell attenuators and other similar devices have appeared on the market.  About which, BTW, reported experiences seem to be mixed.  I and a number of others here have used them with excellent results, while some have reported that they compromise dynamics.  I suspect that the very high input impedance of your BAT would make it more likely than not that they would provide good results in your case.

Regarding the NC400, the last few pages of the datasheet include descriptions of how the surrounding amplifier chassis can be designed so as to provide unbalanced RCA inputs, although the datasheet discourages those approaches as being non-optimal in terms of performance.  If your monoblocks provide RCA connectors, presumably/hopefully they use one of those approaches.  If they provide only XLR connectors, the only safe way that occurs to me of connecting a component having unbalanced outputs to them would be via Jensen transformers, or equivalent, such as a pair of the Jensen model PI-RX, similar to PI-XX shown here but with an RCA input connector, as depicted in the lower right corner of this datasheet.

And in fact if the DAC you end up choosing includes a volume control which seems to provide satisfactory performance, but it only provides unbalanced outputs, you may want to consider using a pair of those transformers and doing away with the BAT altogether. 

Regards,
-- Al
  

Thanks for the follow up guys . One last question . I plan on picking up the a BAT 60/75 tube amp . It is the companion amp to the vk5i . When that is put in i assume volume control will increase ? From what i have understood it is the more the relationship between bat and hypex that is the issue ?