lynn_olson
Responses from lynn_olson
| 300b lovers And of course a part-Mullard circuit is perfectly acceptable for a PP 300B amplifier. Unlike a PP pentode amplifier, though, you need about two to three times as much voltage swing in the driver, so a Dynaco circuit is definitely not the right cho... | |
| 300b lovers Back in 1993 when I was trying many different amplifiers on the newly completed Ariel speakers, I came to the conclusion that a stock ST70 was the minimum acceptable standard for hifi. Most transistor amps fell below this mark, and most tube amps ... | |
| 300b lovers The three-tube 6SN7 circuit board for the Dyna ST70 converts it to a Mullard circuit, with lower distortion and stronger drivers. Since nearly all the ST70 circuitry is on the single circuit board (for both channels), swapping that board basically... | |
| 300b lovers Another walk down Memory Lane. This time, we’ll go into the late Forties, when the Williamson burst on the scene. This English design wiped out all other designs in the USA until about 1955 or so, with the exception of the McIntosh and a few other... | |
| 300b lovers I agree. This is a stable topology, taking full advantage of specialty transformers designed by two of the world’s top designers, and using vacuum tubes that are in current production as well as ample NOS stocks. As mentioned earlier, it’s a very... | |
| 300b lovers And I am very much looking forward to fellow enthusiasts hearing the Raven preamp and Blackbird power amp. I’ve been a voice in the wilderness for about twenty-five years ... neither a member of the SET fraternity (well, maybe on the edge of it) n... | |
| 300b lovers As a minor diversion, I should describe the "Golden Age" amplifiers I keep referring to. This aren’t just the amplifiers made in the Fifties and Sixties; it describes the majority of PP tube amps made since then, including today. There were only ... | |
| 300b lovers Now’s a good time to discus the difference between overshoot in feedback vs non-feedback amplifiers. Despite similar appearance on the scope, they are caused by completely different mechanisms. * Overshoot in a feedback amplifier is quite malign,... | |
| 300b lovers I went through that with the Amity amplifier in the late Nineties. Nice square waves vs sonics. The amp sounded best with NO grid resistor, and the overshoot was a non-factor. Your amp may be different, of course. Keep in mind that music sources w... | |
| 300b lovers Last but not least, although four driver tubes are required, they don’t have to be matched quads. Matched pairs are fine. It doesn’t matter if the drivers in one amp are at 50 mA each and the drivers in the other amp are at 55 mA each. The differe... | |
| 300b lovers Let’s do a little quick math to see how hard the driver is working, compared to an output tube. The gain of a 300B is 3.9, according to this Western Electric data sheet. The interstage transformer has a moderate gain of 1:1.2, so the net voltage g... | |
| 300b lovers If we chose, we could have a switch that would alter the quiescent current for the driver section, so 6V6’s could be accommodated as well. All of these tubes have the same pinout, but the optimal current for the 6V6 is in the 25~30 mA range, while... | |
| 300b lovers The self-bias cathode resistor lets you choose anything between 6L6, KT66, 6550, and KT88. So far, the KT88 is winning, but the KT66 is very good also. We're shipping them with a matched quad of KT88's, but the user can use any matched quad in tha... | |
| 300b lovers The Kootenai is no slouch: a classic Mullard circuit (as used by Marantz and others) with 6SN7 input and drivers, PP KT88’s biased into near Class A, advanced B+ regulators, all on a compact stereo chassis. A clear step up from restored Marantz, M... | |
| 300b lovers Don and I were talking on the phone today, and I realized that, of the four to five key people involved, we might have two centuries of professional design experience in audio. I think Don and I might have a century; I filed my initial Document of... |