Audio Research SP-10 preamplifier Follow-up November 1986
The sound of the Convergent Audio SL-1 is very good indeed (as it should be at $3495)good enough that it can probably be best reviewed by comparing it to its top competition. The Audio Research SP-11 and SP-10 are obvious standards of reference in tube design, and the original and revised Motif MC-7 are good transistor standards of comparison.
Bass: The original Motif MC-7 had excellent bass and lower midrange, with an emphasis on control rather than sheer bass power and dynamics, and the revised MC-7 is as good, and possibly superior in detail. The Audio Research SP-10 is a very close rival to the MC-7. The bass is slightly less extended, but the SP-10 has a faster and more dynamic way of handling bass instruments. The difference between the two is like shifting from midway in an orchestra hall to listening quite close to a small jazz group.
Upper Bass/Lower Midrange: Both versions of the Motif MC-7 make a smooth and coherent transition from bass to midrange. Once again, however, the MC-7 is a bit less dynamic and "live" than the Audio Research SP-10.
It is important to note that this region is one of the SP-10's great strengths in reproducing recorded music: it makes most music seem more natural in this area than the SL-1 or SP-11. The SP-10 has the musically natural smoothness of the Motif MC-7, but is more naturally dynamic and has more life.
This is a damn good reason to not trade in your SP-10, if you were considering such a thing. The upper bass and lower midrange are transition areas that on much equipment seem to lack character and musical detail; when really good equipment comes along it makes you remember that this is the area where all music packs a great deal of its power and emotional impact. All of the preamps involved in this comparison do well in this region, but the Audio Research SP-10 outperforms every preamp I've heard in this key performance area.
Midrange: the SP-10 is slightly too warm and romantic.
Upper Midrange: The SP-10 is just a bit too warm. It makes most recordings sound too good: a fully accurate preamplifier would reveal more detail, without any more emphasis of the upper midrange than is musically natural.
Treble: The Audio Research SP-10 is more forgiving than the MC-7, perhaps a little too forgiving. It again makes recordings sound a bit too much like live music, and a little less like recordings, than it should. It is also slightly lacking in low-level detail in this area, with more air and apparent life in the treble on most material than is really justified.
Soundstage Depth: The SP-10 has a bit less depth than the Motif MC-7, placing instruments a bit more forward.
Soundstage Imaging: The Motif MC-7 is rivaled only by the SP-10 in this regard, and the MC-7 may have superior overall ability to provide the full arc of imaging without any emphasis of the center or sides.
Soundstage Hall Position: The SP-10 and SP-11 have a more forward character, but are both very revealing. If the Motif MC-7 is Row N, the SP-10 is row H, the SP-11 rows E-F. The Convergent Audio Technology is Row F-H.
The Audio Research SP-10 remains the most attention-grabbing preamp ever made. You feel like you are in the best seat in the house even as your mind tells you that the SP-10 may be improving slightly on the signal source to give you this impression.
Overall Dynamics and Transient Life: The SP-10 is very dynamic at moderate listening levels, but loses detail in its noise floor on soft passages.
Sonic Consistency No Matter the Gain: Both the Motif MC-7 and Audio Research SP-10 suffer from slightly higher coloration in their high-level stages than do the SP-11 and Convergent Audio Technology SL-1. The SP-10 can be switched in a number of ways to reduce coloration in the high gain stages, and seems remarkably neutral (until you hear the SP-11). It does, however, add a bit of warmth and apparent imaging detail to everything that passes through it, with this coloration increasing in direct proportion to gain.
The SP-10's phono stage is very consistent with the overall character of the high gain stages, and its sound character doesn't change with cartridge loading, but its gain capability is also clearly marginal with many of the lower-output moving coils. It needs a relatively high output mc, like the Koetsus and Kisekis, and the gain match can be unpredictable. It works very well, for example, with the Monster Cable Alpha 2, but not with the van den Hul MC-10though both my samples measure as having the same output. Using a moving coil with output too low, the SP-10 can suddenly seem to lose energy in the bottom four octaves, lose some of its dynamics, and add a hint of noise.Anthony H. Cordesman