Show Report

Rocky Mountain Audio Fest

Held in Denver, Colorado, September 30 - October 2, 2005

October, 2005

John E. Johnson, Jr. and Cynthia B. Johnson


Page 1

As I said, tubes were a big thing at this show.

This room had horn speakers powered by Atma-Sphere tube amplifiers such as this S-30 ($2,950), which has had a cosmetic change from the older look. This amplifier is Output Transformer-Less (OTL) and delivers 30 watts per channel. The advantages of OTL is that there is no transformer between the output tubes and the speaker. The disadvantage is that the output goes down with decreased impedance.

The second photo shows one of the horn speakers that work well with these amplifiers. Horn speakers work like a megaphone, with the sound being emitted at the small end, and the sound coming out to the room from the larger end. In this case, it is a Hartsfield front-loaded corner horn speaker ($30,000/pair). This model is built by Classic Audio Reproductions. We saw a lot of horn speakers at this show. Some of them are not nearly as expensive as this one. The advantage of horn speakers is that they are very sensitive (100 dB/w/m or higher) which means you can get lots of volume from low powered amplifiers, e.g., less than 10 watts.

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