This may sound a bit silly but why are so many

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Yeah, what Tomcy6 said. Even if you ever do get everything 'just right', something new comes out and your curiosity gnaws at you incessantly.

As good as the Ref 40 is, ARC eventually had to come out with a model that surpassed it. I'm always thankful when the new ARC preamp models come out, the prices of the pre-owned previous flagship models start to tumble and I get to move up the food chain a little. I should be ready for one of those pre-owned Ref 40's in a couple of years.
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Mich4t, you are correct that a sale of a preamp can be the result of wanting the new and improved model. To this day I can't understand why the AR reference system I listened to did not move me. I asked the dealer to try a different CD with no improvements. I thought also that the Wilson speakers could quite possibly be a bad match for the audio research components.

It is as good as they say & no one's buying mine! That said, everyones taste is different, several early units were sold to the trade at a discount so they won't lose much, others like trying the "flavor of the month", and at this price level for many who would buy one, cost isn't so much of a consideration whether new or used. I don't think the Ref 10 will be considered an upgrade, but ARC sold many more limited release Ref 40s than they anticipated, they probably felt they had to follow it up with something.

One reason some may not find it their "cup of tea" is that the Ref 40s holographic space presentation wreaks havoc with some processed music that wasn't carefully mixed. I don't find it tubey and I say that having never owned a tube preamp. It may not be the best out there for someone who likes rock music and lives only for leading edge detail, incisive clarity, and pure transient speed.

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Barrysandy, let's talk in about three years. I'll be ready for the Ref 40 by then, and your curiosity about the new models will have gotten the best of you by then.
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Mitch. Not happening! My wife will get the best of me (just like Lorena Bobbit) if I ever buy any stereo component this expensive again. Regards Barry