Convergent Audio Technology SL1 Renaissance preamplifier Page 3
Setting up the Renaissance in my system was pretty simple: Take off the cover to make sure the Gain switches are set to Low (they were) and the MC/MM switches to MC (they were); and transfer the input and output cables from my SL1 Ultimate to the SL1 Renaissance, making sure to plug the CD cables into Input 2 and the output cables into the Direct outputswhich, unlike the A/V outputs, don't have a relay in the signal path. I compared the A/V and the Direct outputs and, believe it or not, there was a difference: the A/V output had very slightly less clarity. Sharpeners, you have been warned.
The Renaissance allows for loading the phono input with resistors different from the standard 47k ohmsthey're in the form of RCA plugs, to be plugged into the pair of MC load jacks next to the phono input jacks on the preamp's rear panelbut the load recommended for my AudioQuest AQ7000nsx cartridge is 47k ohms, so I didn't have to use them. All components, including the Renaissance, were plugged into a PS Audio Power Plant Premier power conditioner.
I did no critical listening and made no direct comparisons with the SL1 Ultimate until after several weeks of casual listening. If there was an audible break-in effect, it was relatively small.
Listening to CDs
I call it the reviewer's nightmare. You receive a component for review, and, after extensive listening, you discover that it is literally perfect in every way. Not just excellent, not just the best you've ever heard, but perfect, reproducing every aspect of the source material, adding or subtracting nothing from the signal except for increasing its levelor, in the case of a speaker, producing sound that is a perfect sonic replica of the input signal. How would such a review read? And how would this experience influence any future reviews you might write? I mean, once you've heard the, ummm . . . ultimate, there is, by definition, no room for further improvement. Any succeeding reviews of products in that category would have to consist of descriptions of the ways their performance falls short of that perfect component. The best you could hope for would be that their performance would equal the ultimate's, because of course it couldn't be better. Might as well hang up your reviewer's hat.
Fortunately for me and for other reviewers, the above scenario has not yet come to pass. The CAT SL1 Ultimate was and is an excellent preamplifier, probably the best I had heard up to the time of its review. But comparison with the SL1 Renaissance has shown that it was possible to improve on its soundsignificantly, in fact.
During that first period of casual listening to the Renaissance, I did my best to put aside my critical attitude and just listen to the music. I made no comparisons with the Ultimate, and the CDs I played ranged widelyhardly any were of the "audiophile" variety, and none was one of the reference recordings I use for direct comparisons. You might say I was in leveler mode. Still, when you're used to judging sound quality, it's difficult to put aside that attitude entirely, and it wasn't long before I'd formed the definite impression that the Renaissance was as good as, and very likely better than, the Ultimate. From then on, it was a matter of determining how it was better.
If you use highly sensitive loudspeakers, the first impediment to good sound is noise. My Avantgarde Uno Nanos' sensitivity exceeds 102dB. This means that even a small amount of noise generated by the preamp, combined with noise from the power amp, will be much more audible than if I were using a typical box speaker with a sensitivity of, say, 86dB.
In the past, with different electronics and an earlier version of the Uno, reducing noise was often a struggle (grounding or ungrounding different components, changing cable routes, etc.), and I sometimes ended up having to reconcile myself to the fact that the music was not going to emerge from a completely silent background. But with the combo of Ayre, SL1 Ultimate, Audiopax, and Uno Nanos, I'd gotten lucky: the level of background noise was so low that I didn't have to worry about it. I was curious to hear if the Renaissance would be even quieter.
John Atkinson reports on his measurement of the Renaissance's signal/noise ratio in his "Measurements" sidebar, but I did my own informal subjective test to evaluate the Renaissance's contribution to the overall noise of my system. With no CD playing, I set the volume to what would be an average listening level, and compared the noise with the preamp's Mute control engaged, then disengaged. I did this with the Ultimate and the Renaissance, matching volumes as well as the preamps' discrete volume controls would allow. (The Renaissance's volume setting was 0.5dB higher.) Result: With either preamp, turning Mute on and off had no audible effect at the listening seat.
I then repeated the test with each preamp's volume control one click up from the "average" level. Again, muting or unmuting the preamps had no effect. Even two clicks up, which represented the highest level I would want for listening, the Mute control had no effect on the level of noise coming through the speakersthe noise was virtually inaudible at the listening seat. (This is as much a tribute to the Audiopax monoblocks as to the CATs.) Conclusion: If you're concerned about keeping audible noise to a minimum, either SL1 will do an excellent job.
I then donned my sharpener hat to do some more critical evaluation. For A/B comparisons, it's good to have two components' volumes matched as closely as possible (ie, within less than ±0.1dB), but the volume-control steps of the CAT preamps are too coarse to allow this. Instead, I matched the volumes as much as the controls would allow (0.5dB), then "bracketed" them: the preamp with the lower volume in the initial comparison had the higher volume in the subsequent one. Conventional audio wisdom says that the music that's louder will tend to sound better, but I haven't found that to be the case. I guess I've learned to mentally compensate for volume levels. Still, if there is such a bias, the bracketing procedure should control for it.