lynn_olson
Responses from lynn_olson
| 300b lovers As for the tech, none of this is difficult. They will know how to connect and bias the floating paraphase phase inverter ... plenty of old schematics out there ... and the rest is a matter of chassis space and heater current for the new drivers. ... | |
| 300b lovers Unfortunately, revising the driver away from the usual single 12AU7 means another hole in the chassis, and a pair of octal sockets at that. And split power supplies means another power transformer and rectifiers, although it relaxes the endless se... | |
| 300b lovers The interesting thing is that "conventional" amps like PP KT88’s can be substantially improved as well. For example, floating paraphase phase inverters instead of split-load inverters or Mullard long-tail pairs. The phase division isn’t as precise... | |
| 6DJ8 vs. 6922? They are interchangeable. The 6922 is the commercial-grade version, a step above the consumer-grade 6DJ8. In practice, it’s been a half-century since the phone company, avionics, or the military used these tubes, and they were replaced by FETs in ... | |
| 300b lovers Don and I reflected on the optimum interface between the Raven preamp and Statement power amps. We obviously wanted the highest-quality interface directly between the two, while retaining compatibility with the rest of the audio world. There’s an... | |
| 300b lovers The preamp, since it has balanced transformer-coupled inputs and outputs, breaks the ground connection between components, reducing hum, as well as RFI breakthrough and buzz. That’s why transformers are often used in noisy professional application... | |
| 300b lovers It’s been fun writing about the zigs and zags that took Don, myself, and the team at Spatial to where we are now. More to come? Who knows? The preamp (with remote control thanks to Khozmo) and power amps are off to a good start. Phono preamp? Ooo... | |
| 300b lovers The evolution from the original Karna amplifier, built by Gary Pimm in 2002 and designed by yours truly, to where it is now, is a desire for rationality combined with reliable performance. The original was a proof-of-concept, the kind of thing I’v... | |
| 300b lovers I’m not surprised. The great enemy of transformers are high impedance, which decreases bandwidth on both ends of the spectrum, and increased insulation resistance, which takes up room on the winding stack. Both act to increase the size of the core... | |
| 300b lovers Since the 300B fits into the KT88 ecosystem, the same choices for power and output transformer apply, except you’re not messing with ultralinear connections, and some thought (well, a lot of thought) needs to be applied to the filament circuit, wh... | |
| 300b lovers The 845 is not happy at 500 volts. It is a (low-power) transmitter tube, and is designed to work from 800 volts (minimum) to well over 1000 volts. Once you go over 500 volts, construction, and the parts required, are a whole different world. It r... | |
| 300b lovers Which I guess leaves the question why does the input stage have the topology it does. The quick-and-easy approach would be a Mullard-style long-tailed pair or differential stage, or maybe borrow from Williamson or Dynaco and direct couple a half-6... | |
| 300b lovers The 300B ... all of them ... quite happily accept at least 20 volts of positive grid drive. This is not secondhand info gleaned off the Internet, I’ve seen it for myself on a Tektronix scope screen back in the Nineties. I was frankly surprised, be... | |
| 300b lovers You want a technical presentation, here’s my talk at the 2004 European Triode Festival: 2004 ETF Presentation As for the lengthy previous post, I am not sure about the impact of dynamic variations in output impedance. One way to measure the impa... | |
| 300b lovers By the way, my own little hypothesis about output impedance of SET amps varying over the signal cycle could be completely wrong. Transformers do store energy, which is why the primary easily swings well above B+ voltage. So the transformer itself ... |