lynn_olson
Responses from lynn_olson
| 300b lovers By the way, there’s a very intelligent discussion of the latest John Curl/Parasound amplifier design here: Parasound Discussion Note they are talking about fully isolated input+driver sections with 117 volt rails. That might sound insanely high ... | |
| 300b lovers If you’ve been curious the kind of things two designers discuss with other, the previous posts give a simplified example. Sonics, different circuits and what they sound like, and reliability. It's also an example why collaborations between designe... | |
| 300b lovers One variant we did not try was a center-tapped inductor to load the 6SN7 plates, and direct coupling between the input and driver tubes. That requires a high B+ voltage for the driver, but that’s no problem when the input + driver have their own p... | |
| 300b lovers It may strike some readers as weird that Don and I are taking a minimalist approach to a PP amplifier, more like a SET than a typical PP. The signal path is simple: Optional SE/Balanced input transformer -> Balanced 6SN7 -> Interstage #1 -&... | |
| 300b lovers That’s a subtle aspect of feedback theory that is often overlooked. The summing node must be distortionless, and also free of overshoot or slewing artifacts. Applying input signal to a grid, and feedback to the cathode, impresses tube distortion (... | |
| Spatial Audio Raven Preamp Happens all the time in the small-production-run solid-state world. Oversights in manufacturing like no heat-conducting paste between transistors and heat sinks, for example. Or a wave solder machine not properly set up for EU-required leadfree so... | |
| 300b lovers Ralph, you’re the acknowledged OTL expert. How does an OTL amp work without feedback? I’d like to know. The last I checked, tubes designed for series regulator use like the 6080, 6AS7, or the Russian 6C33C have a Zout on the cathode side somewhere... | |
| Spatial Audio Raven Preamp Oh it blew a fuse all right. After the output section was completely destroyed, and a massive DC pulse killed the woofer. This was European oligarch-class audio gear from a well-known manufacturer. The manufacturer is still around, twenty years l... | |
| Spatial Audio Raven Preamp The anecdote is true, not fictional. I was there and saw it happen. Not surprisingly, the preamp and power amp were all solid-state and were stupendously expensive, in the $100,000 range. As we old-timers know, price does not guarantee quality in... | |
| 300b lovers To recap, there are different challenges associated with low and mid-frequency distortion vs high frequency distortion. HF distortion is very often caused by nonlinear current delivery into a capacitance, and stray capacitance is everywhere in aud... | |
| 300b lovers Something both transistor and tube amps share are performance limitations set by current available to drive a capacitance. In a transistor amp, that will be the dominant pole capacitor associated with the second voltage-gain stage. The current ava... | |
| 300b lovers Interesting SET that harks back to the original Western Electric 91A, which also used feedback to get the desired performance. I have mixed feelings about cathode follower drive: the output impedance of the CF is low (probably 100 ohms or so), bu... | |
| Spatial Audio Raven Preamp The most dangerous of all are DC-coupled preamps and power amps. If the DC servo system in a preamp fails, the failure can propagate all the way to the loudspeaker. I saw this happen when I was visiting the home of a reviewer. It took out one chan... | |
| Spatial Audio Raven Preamp Another small note: conventional tube preamps can be dangerous for transistor amps unless they have an automatic muting relay with a timer circuit. A conventional tube preamp with cathode follower output typically has the output node (the cathode)... | |
| Spatial Audio Raven Preamp Don and I are pleased that Raven owners have an equal choice between RCA-input power amps and XLR-input power amps. The Raven treats both the same, so the sonic choice is on an equal footing. Classic vacuum tube amps almost always have RCA inputs... |