Any help on Threshold s550e amp?

The heat sinks on the S550e, which I am auditioning, run more than slightly warm and much warmer than the S300. The hand can remain on them, but it will be quite warm. The dealer does not carry the amps you mention, but may have a McIntosh 352 that I can compare. After some extended listening, I will also go back to the S300 to see again what differences I can hear. Thanks for the comments.

A couple of years ago I upgraded from a S/300 series II to a S/350e. The S/350e idles hotter than the S/300. The reson: the e series amps operate at a higher bias than their previous interations in the S series. Here's a tidbit from the e line manual: "The tracking accuracy of the optical bias circuit has allowed the biasing of Threshold S/model amplifiers to such levels that are now designated class A/AB in operation. This means they will function as pure class A amplifiers until about 20% of their instantaneous power rating into 8 ohms, and operate as class AB beyond that point. At idle they generate as much energy as their class A counterparts, but they operate at higher voltages so as to deliver higher wattage to the loudspeaker." For what it's worth my Threshold is a keeper and is not for sale. The list price of the S/550e was $6300. If you can get a mint S/550e for $2100 or less that would be a good deal.

Jdh, I would compare the Threshold to the Mac 352, because the Mac is a very good amp with a large soundstage, good bass, nice body to instruments, a little soft on top. I'd be interested in your impressions of the two amps. If the Threshold compares, buy it.

It is now obvious to me that the S500 I heard, that was updated by a Threshold technician to an 'e' series & supposedly biased heavily into class A, was a lemon. It sounded dead & dull, and it ran so cool, I knew something was not as it should be.

Let us know your audition results.

Those commens are really helpful. The demo of the Mac will probably not happen for a couple of weeks (a dealer in transition, etc). If and when I hear it, will be back in touch. Thanks again.

Finally. I have now had a chance to listen to both the s550e and the Mac 352. To my aging ears, the Threshold had a tighter bass and just a bit less color in the midrange, but these differences were very slight. I have chosen to purchase the Threshold at a price of about $2300 after netting out the value of included premium cables from Esoteric and a five-year warranty from the dealer. The Threshold unit was used as a high end demo while he was carrying that line and is in mint condition. Even with an aggressively priced Mac 352, at about $3300, to have the Threshold plus an extra $1k left over made it an easy choice to me. Please understand, however. The Mac 352 is a very good amp. With thanks to all who commented and I hope this is useful to others.