lynn_olson
Responses from lynn_olson
| 300b lovers Don did a marvelous job here. It’s actually quite functional, with a clean and direct front-to-back signal path, and with all wires in the balanced circuit equal length (yes, he went to that much trouble). You can infer that from the top plate. T... | |
| 300b lovers This is very close to the production version. It is simpler and more straightforward to build than the shoebox format shown at the PAF show ... more spacious, more direct layout, and the power supplies are confined to their own section of the amp,... | |
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| 300b lovers My first experience of a 300B amplifier was back when I was writing reviews for Positive Feedback magazine back in 1993. It had grown from a 4-page mimeographed club magazine for the Oregon Triode Society to a fat 100-page periodical with cartoons... | |
| 300b lovers Let’s talk technical about DHT filament power supplies. My friend John Atwood built a low-RF filament supply a few years back (100 kHz or so), but he made the discovery that the filament inductance of DHT tubes was all over the place, making it di... | |
| 300b lovers Although I don’t enjoy "tuning", it is an unpleasant necessity for speakers and power amps. For reasons that are not clear, various brands of metallized polypropylene capacitors sound quite different from each other, and there is little correlatio... | |
| 300b lovers I should mention SE tuning is not the same as balanced-amp tuning. The dominant coloration with SE are the tubes themselves, and it requires artful selection to avoid heavy additive coloration. The fad for 2-stage SET amps makes this worse, since ... | |
| 300b lovers Areas for improvement: The 5U4G rectifier is not ideal. I’d use HEXFREDs, high-voltage Schottky rectifiers (Don’s choice), or damper diodes for the 300B plate supply. Any of the three will have more dynamics and more vivid tone colors. The improve... | |
| 300b lovers I should note my description of feedback circuits is a grossly oversimplified, non-mathematical overview of a complex subject. For the curious, read about how op-amps are stabilized, and the concepts of loop gain, excess gain, dominant-pole compen... | |
| 300b lovers By way of comparison, neither the Raven nor the Blackbird use any form of feedback, either local (around the tube) or global (around the entire amplifier). The incoming audio signal only flows forward, with no secondary paths around the circuit. F... | |
| 300b lovers Negative feedback is the right choice for the vast majority of amps, particularly direct-coupled solid-state, where you can pile on the gain and use that "excess gain" to minimize distortion via feedback. To oversimplify, if you have 20 dB (a 10:1... | |
| Why Can't Modern Tube Manufacturers Make a Proper Tube? Looking back at the 1950's and 1960's, remember, everything was made with tubes, except for mainframe computers and exotic aerospace applications. And they weren't all that cheap ... multiply the prices by ten to get a better idea of the real cost... | |
| I'm going to buy my first tube amp. I need honest blunt opinions Depends how power-hungry your speakers are, and if they have high-order (18 dB/oct and 24dB/oct) crossovers. If the true Theile/Small efficiency is less than 87 dB/watt/meter, and if the crossover is high-order or employs notch filters, sorry, tub... | |
| 300b lovers It’s a safe guess it’s about the same ... in the 60 to 80 pF range. Most true 3-element triodes, triode-connected beam tetrodes, and triode-connected pentodes fall about there. So-called ultralinear mode is probably about half that. Pure pentode i... | |
| 300b lovers Lot of solid-state in there, probably not my first choice. |