lynn_olson
Responses from lynn_olson
| 300b lovers Alex, remember, you cannot harm your amplifier if you completely remove the grid-load resistor. With a transformer, runaway from DC instability is impossible. There is always a DC path through the secondary ... as long as the secondary is intact. ... | |
| 300b lovers Try removing the 56K load resistor entirely and give it a listen. You might like it better. Remember, with conventional signal sources, there is almost no ultrasonic content, so the ringing in the transformer is never stimulated. And getting rid t... | |
| 300b lovers Scope pr0n. Same pix as earlier, just more zoomed in. Don Sachs scope photo of Blackbird at 30% power (8 watts) at 1 kHz. Zero feedback, with no grid resistors to "trim" the response. | |
| 300b lovers A quick note: Don and will not be making the part-Mullard or the suggestions made by others in this thread. The Raven and Blackbird are where our attention is, and that’s where it will stay. Our focus this year, and the next, is getting production... | |
| 300b lovers The problem with two successive stages that are balanced and DC-coupled to each other is that DC drift is a big deal. A 1 volt shift on a 150 volt plate is normally inconsequential, but becomes a serious concern when the grids of the following sta... | |
| 300b lovers There's no feedback, and there's gobs of 2nd-harmonic distortion. Parts coloration works for or against that 2nd-harmonic distortion. Also, because power-supply rejection is zero, power supply coloration is right in your face. Driving DHTs takes ... | |
| 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... |