I've used the EX-M7 with both the Supratek Chardonnay via XLR and the Don Sachs Model 2 via RCA and had no problems with either. The problems that Srajen had when he tried both his Nagra and later his Vinnie Rossi preamps had to due with the type of tube regulated power supply they use. You should have no issues with your preamp. The EX-M7 is a single ended amp and the XLR inputs are strictly convenience. I use them so I don't have to swap cables out if I substitute in the BHK 250 which is fully balanced.
Thanks Jack, you were spot on. I received my new EX-M7 a couple of weeks ago and it has had no issues being paired with my Herron VTSP3 tube preamp.
Fresh out of the box the M7 sounded promising but a little flat and stiff. From around 15 to 35 hours it started to sound better but there was some glare/hardness. Now at 48 hours the glare is gone and it is starting to sound seriously good. Dynamics and leading edges are so quick and snappy yet totally realistic. Strings, horns, pianos, vocals are all so utterly natural sounding, electric guitars are amazing. There is a wonderful purity and lifelikeness to everything. A natural warmth, weight, organicness, immediacy and vitality, even juiciness at times. Surprisingly (to me), I'm not missing my tube amp at all. I haven't reconnected my sub yet but the depth, weight, texture and growliness of bass is making it easy for me to wait until the EX-M7 is fully burned in before doing so.
The combination is significantly better than the EX-M1 I had previously. The EX-M1 was impressive in ticking off the requirements on the audiophile list but couldn't quite get me to believe that I was listening to real music and to just relax and drink it in. This combo does that easily and consistently.
My floorstanders are rated 93dB/8R (the same as your Otellos) and I still have a little too much gain overall. The DAC is 2.5v from SE output, the Herron VTSP-3 tube preamp is 8dB gain on the low gain setting, the EX-M7 is 26dB gain (tube amp was 29dB). Room is approx 440sq.ft and open to other rooms but even with Harrison Labs -12dB inline attenuators on the EX-M7 SE inputs, my loudest listening level is typically between 35 and 45 (out of 100).
I would love to hear the Athena (unity gain) with the EX-M7 in this system as it would drop the overall gain and its fully balanced design would enable me to use my Spring DAC's balanced outputs (which Spring owners claim sound better). As the VTSP-3 is quite neutral and non-tubey sounding anyway, I probably wouldn't lose any "tube sound" but the lower noise floor may improve details, dynamics and immediacy even further.
Has anyone here tried an Athena with the Kinki EX-M7, or compared Athena to Kinki EX-P27?
Jack, do you have any excess gain issues with the EX-M7 and your Otellos?