Cary SLP-05 pre + Krell 302e/402e sound? Should I consider a different power amp?

John Atkinson’s measurements of the SLP-05 were very different than the published numbers for gain and output impedance. For output impedance he measured...

...1500–1600 ohms in the midrange and treble, rising to 3400 ohms at 20Hz [unbalanced], with similar if slightly lower figures for the balanced output.

And he measured gains that were much lower than the numbers that are presently specified, and that also differed from the lower numbers that were specified when the review was written in 2006. Per his comments tube selection may have contributed to the gain discrepancies that were noted when the review was written.

In themselves none of these things should matter with the Krell amps that have been mentioned, given their very high 100K unbalanced and 200K balanced input impedances, and their moderate specified gains of about 25.5 db. However after noting some oddities in the measurements JA concluded by saying:

Though it has some anomalies, such as being happier with 10k ohm loads than with 100k ohms, the Cary SLP 05 offers respectable measured performance from its unbalanced jacks. I was a little disappointed with its behavior in balanced mode, however.

Good luck. Regards,
-- Al

Hi Charles,

Yes, it is puzzling how a component could be spec’d so inaccurately, especially one that is so highly regarded and was designed and originally spec’d while the company’s very highly regarded former designer was still there. Those original specs, BTW, included the same 400 ohm output impedance number that is still published, as you correctly indicated.

One point I would add for the OP is that if he does go with the SLP-05 the high output impedance at all frequencies will tend to magnify certain interconnect cable effects. So it would be preferable to avoid particularly long lengths of interconnect cabling between it and the power amp, especially if the particular cables do not have low capacitance per unit length. The interaction of the high output impedance at high frequencies with high cable capacitance would tend to introduce at least a slight amount of rolloff and/or undesirable phase shifts in the upper treble region. And that would apply regardless of whether balanced or unbalanced interconnections are used, since the two output impedances were described by JA as being similar.  Something like 15 feet of cable having 35 pf/foot capacitance (525 pf total capacitance) should be ok though, at least as far as that effect is concerned.

Best regards,
-- Al