Conrad Johnson vs Audio Research vs BAT vs Cary

If your T400 is DC coupled, you might want to consider how likely the tube pre is going to pass on DC.

Thanks so far for some very interesting answers. Another Agoner emailed me to say he had tried the BAT VK-5i with the Threshold and they were a poor match (probably impedance mismatch). Elsewhere on forums, I think it has been suggested that there is an impedance mismatch. Is anybody aware if the newer iterations of BAT preamps (e.g 31SE, 32SE, 3iX) might circumvent this problem?

If you want to use a tube preamp you will have to run it single ended. The balanced input impedance on the Threshold is only 600 ohms. Any CJ, ARC, or Cary run through the RCA inputs will be fine. The 31SE, 32SE and 3iX can also be used, but not through the balanced inputs.

My CJ Premier 16LS2 doesn't sound overly warm at all. When I first got this preamp my reaction was "it is not warm enough!" Everyone described CJ to be overly warm, but not in my system and to my ears. It's just slightly warmer but much smoother than SS McCormack preamp it replaced. I understand the older vintage of CJ gears are much warmer sounding. As far as detail, it has 95% of detail compared to Unidisk driving power amps directly playing SACD. I don't miss any detail missing in normal listening.

If you are thinking about a Cary SLP-98, the F1 version is not as warm as the standard version. I had a friend's SLP-98 F1 in my system for a bit and it really sounded lovely. A bit colored, but in a way that fit in very well with my system.

At the same time I had an ARC LS-26 I was auditioning. At least when mated with my old Pass X250.5, the LS-26 was rolled off in the low bass and had a strident courseness in the upper midrange that was bothersome. So, I agree with other posters here. There are many excellent preamps out there, but you really do need to try them out in your system. Preamps can sound quite different from one system to the next based on the electrical interactions of the system.

Good luck,
Alan