Tubes in Audio Research Equipment: 6550

Wolzst- I think you'll find that most current tube amps are far more neutral than tube amps of the past. Better passive components have allowed designers to obtain far more detail and control from recent tube equipment. Of course, most tube products still benefit from modifications and tweaks. From improved parts quality, NOS tubes, increasing/improving the power supply, etc... one can radically alter the sound of any tube product. As for the sound of the tube, it is the circuit combined with the tube that produces the sound. Although certain characteristics can be attributed to a particular tube brand and type, it's always best to let your ears be the judge in the context of your system to determine if you like one tube over another. In general, I prefer the sound of NOS tubes in my equipment over current Chinese, or Russian tubes. Just my .02

Very clear and neutral with a little warm glow around the instruments. Seems like these are clear in all ranges whereas a lot of tube amps I've heard are ultra-clear in a small midrange window. Check out the svetlana home page and thetubestore.com for some tube sound interpretations.

I find that the 6550 tubes, while having good dynamics and deep bass, are very thin and cold sounding. Improvements are the cousins to these tubes - KT88, KT90, KT91, etc. While a bit of power is sacrificed, they tend to be more musical. The only reason the 6550 tubes are used so much, is due to the wide avilability of them and the number of suppliers. There are better tubes that produce much better "musicalility" such as the 6C33s. The problem is there is only one source that I am aware of. These tubes are used in the better products, such as the Lamms and the BAT equipment.