----- Original Message ----- From: "phillip holmes" <insuranceman@xxxxxxxxxx>
Sorry to spout off late. Tubes can be just as quiet as transistors. I've heard noisy examples of both. With classic tube stuff, you're going to have to replace the power supply caps. They're crap. The ESR of modern electrolytic caps are several orders of magnitude better than what was available back then. As Tom points out, DC filaments are the way to go. There were high end preamps back then that used DC on the filaments and choke regulation in the B+. One of my favorites is the Harmon-Kardon Citation 1. It has adjustable turnover and rolloff. It's very quiet and the sound remains constant as the tubes age because of the judicious use of local/loop feedback. The zero feedback stuff is BS--they'll always be prone to tube aging and noise. If you have to rebuild one of these, they're very crammed with parts, so quite a chore to work on. There are upgrade kits available for these that will replace the nasty electrolytic caps, the coupling caps and some other noisy parts. A complete rebuild would take hours, but when you're done, it'd be world class. I have one that'd covered in 20 years of dust. One of these days.... It uses stepped attenuators for tone controls. I doubt anything like this, made as an audiophile product, would be affordable. Just looking at the parts list, I'd bet it'd run at least $3k.
http://www.drtube.com/schematics/harmankardon/cit1.gif
http://www.quadesl.com/refurb/refurb_hkCitation1.html
The point is here...that if both tube hardware and solid-state hardware can produce essentially-undistorted amplified version of sound-signal input, why should there be any reason to choose one or the other?
As a user of intentionally-distorted tube amplifiers (for harmonica playing)...I know that vacuum-tube hardware offers a much more endurable version of distortion than does its solid-state equivalent. However, if we design amplifiers of either sort so as to produce effectively undistorted output...there should be no audible difference between the two. At this point, it becomes more a question of nostalgia... the same thing that inspires me to seek out 78's of performance for which I already own master-pressing reissue discs!
Steven C. Barr