lynn_olson
Responses from lynn_olson
| Spatial Audio Raven Preamp They are custom-design Cinemag, optimized for our circuit. They are not off-the-shelf parts, which have bandwidth problems with the output impedance of the 6SN7. The 6SN7 is one of the best tubes ever made, but is not easy to match with most tran... | |
| Spatial Audio Raven Preamp I hope you folks like the Raven (which are built and sold by Spatial Audio Labs). It’s a miniature version of the power amp, with one stage of gain instead of three. It has both RCA and XLR inputs, with the balanced input going straight to the 6SN... | |
| Don Sachs Owners Thread The DS Valhalla and Kootenai are hidden gems. I didn’t design them, that’s all on Don, but Spatial is selling them at very fair prices, considering what’s inside ... point-to-point wiring, high-end caps, a classic circuit, and an all-octal tube li... | |
| Halcro update I find it interesting that an amp with ultra-low distortion still has scope for subjective "tuning" ... which makes me wonder how it's done. There's something in there the test instruments are not measuring. | |
| 300b lovers Well, keep in mind most LP’s were cut with spherical styli in mind ... specifically, the Stanton 681A with spherical styli. Over in Europe, it was the Ortofon SPU with a spherical stylus. Both were used to play the lacquer once for quality control... | |
| 300b lovers A quick note on the complex variable equalization seen on the Citation I: people who had extensive 78 and pre-1955 LP collections had records with wildly varying equalization curves. By the time of the stereo LP in 1958, the world had settled on t... | |
| 300b lovers Before getting lost in the weeds on balanced vs single-ended phono preamp design, it might be useful to review the general types and look at their advantages and disadvantages. 1) The most common is a high-gain stage with RIAA frequency-shaping f... | |
| 300b lovers Very pretty! Which driver tube? | |
| 300b lovers Just to confirm, the Raven and Blackbird do NOT use the Acrosound circuit shown above. The signal path is considerably simpler. | |
| 300b lovers Acrosound UL-II schematic. Note the input 12AX7 is direct-coupled to the 12AU7 driver stage, so DC drift from internal 12AX7 mismatch could be a problem. Technical analysis: The input signal goes to the top half of the 12AX7. The bottom half is c... | |
| 300b lovers If all these transformers disgust you, or you want to use local or global feedback, you can re-visit the Acrosound schematic from the late Fifties. Three stages, all differential, each RC-coupled to the next. It can be easily updated with modern c... | |
| 300b lovers In essence, the signal flow is: Complementary Pair of 6SN7 sections -> Signal is re-summed in the transformer -> Complementary Pair of triode-connected KT88 drivers -> Signal is re-summed in the transformer -> Complementary Pair of 300... | |
| 300b lovers Ralph brings up a very good point about feedback: the underlying theory assumes a distortionless summing point. (The summing point is the comparator input between signal input and the sampled output.) Any distortion introduced at this point of the... | |
| 300b lovers Yes, it’s difficult to get people to understand that Class A push-pull is quite a different animal than the much more common Class AB push-pull. I understand the reasons for Class AB ... it’s much more efficient, but Class A working is not the sam... | |
| 300b lovers Wow, is that the first Atma-Sphere with an output transformer? Sounds like the 300B amp is well on track, and I imagine the next version will have current sources in the appropriate positions. I’m curious what your experience with a high-power cu... |