mbl 6011d or arc ref 3 or dartzeel preamp?

I own an Audio Research ref 3 and one year ago I also tried it with the Dartzeel amp. Best sound was using the umbalanced RCA input with the ref 3 in the invert position, but when the Dartzeel preamp with the BNC Dartzeel interconnect cable replaced the ref 3 there was a clear improvement in bass and sound "fluidity". I did not keep the Dartzeels as they did not have power enough for my speakers, but I think they work as a system.
When using the Dartzeel preamp try the umbalanced inputs - I found that the balanced input did not sound as good the RCA one.
BTW, I got excellent sound from the Dartzeels using both Audio Research CD7 and the Nagra CDP.

I've had both 6010d and arc-3. More romance with arc, more flexibility with MBL.. and less noise. I think the soundstage wider with arc, deeper with MBL ... I could absolutely live with either although as my 101s are tipped up a bit in the treble, you hear the tube noise more.

I'm really puzzled at how these three preamps came to be in the short list- they seem so different.

Balanced line offers the flexibility of extended cables without degradation, and the balanced line system was devised with the intention of eliminating interconnect cable problems! IOW, a proper balanced line setup will allow you to use an inexpensive cable to very good effect- that is what it is for, and how Mercury, RCA, EMI and others were able to make such fabulous records long before the existance of a high end cable industry.

FWIW we have a customer who has the DartZeel and uses it with our preamp (the MP-1) which is fully balanced. He is very happy with the setup, so a balanced preamp will work fine with the DartZeel no worries.

I use my Rowland Coherence II preamp, which is fully differential balanced, to feed a darTZeel, but I want to make an important point. The "Version 1" DarTzeel had XLR inputs, but merely for convenience for those who had balanced cabling - it was essentially a single-ended input (I can't recall what Herve did with the third PIN). The Version II, on the other hand, added input transformers at the XLR connections. They provide the advantages of noise cancellation inherent in balanced cabling, but they are still terminated into a single-ended circuit.

Herve advocates first the 50 Ohm connection, which was designed for use with his darT preamp (I have a set of 50 Ohm cables that I have used because my Rowland has a 50 Ohm output impedence, but I think they were loading down the preamp too much and I went back to balanced). If that is not possible, he suggests the single-ended inputs. The last choice would be the XLR inputs, which he does not prefer because, like all transformers, they put a lot of wire between the interconnects and the input circuit - he says the single-ended input is cleaner.

In any event, yes, the darT can be run from a balanced preamp, but the Version 2 is better set up for it.

Have you considered buying a pair of valve mono blocks, every time I go back to valve power amplifiers the music flow comes back into my room, some say Clarity is King but with Valve amplifier Musicality is King.

I would recommend auditioning a pair of Quicksilver V4 valve mono blocks with a very good valve preamplifier, then compare this sound to the DarTZeel sound?