Leaderboard

Second day of packing our U-pack-it truck. They dropped it off yesterday at about 2:00 pm EDT and as of 5:00 pm EDT today we have approximately 75% of the house packed up and 99% of the heavy, bulky shit. Now sitting down for an adult beverage.

I've posted this before, but Carl Sagan's commentary is worth repeating here. The image is called Pale Blue Dot, and was taken by Voyager 1 from about the same distance Neptune (6 billion km). Although the Earth is clearly blue, it is actually only 0.12 of a pixel in Voyager's camera. "From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every "superstar," every "supreme leader," every saint and sinner in the history of our species lived there--on a mote of dust suspended in a sunbeam. The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand. It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we've ever known."

Hiromi, nuff said.

Dual 75" monitor setup.

Hello everyone, it's been a while... busy life, covid, work, supply chains, mouser, jlcpcb, etc... Anyway - the power supplies are finally done and tested: +21,04V and 21,01V. Transformer is a dual 22V/50VA. The rectified and smoothed voltage to the 7812 and 7912 are at +/- 36V DC, that's a hair too much. Hopefully that will drop a little when the amplifiers are connected. That's the next step. Cheerio!

The most shocking thing about that is that Sean Penn has an Oscar.

Sean Penn: I’ll smelt my Oscars if Academy doesn’t let Zelenskiy speak https://www.theguardian.com/film/2022/mar/27/sean-penn-oscars-zelenskiy-ukraine

Spotlight doesn't index network drives on macOS Monterey. This is a complete PITA if one has, say, 5ish TB of FLACs on a network drive.

@johnwmclean I changed the resistors so that the bias voltage across the 20 K resistor is 24.3V, the same level as the original circuit when powered at ±450V. The VGS of the SiC FETs are about 4.0V at idle (17.2mA) and Vce of the PZTA42 at 14.75V. @JoaMat I'm building this amp for the fun of trying different alt parts. As long as both channels have close enough performance, I can confidently move on to try something else. I didn't observe power-on Vce excursions, so I guess medium-voltage medium-power NPNs such as ttc004 or ksc2690 should work fine here.

This "Normal" behavior has been my experience as well but I also found the magnitude of offset drift is closely related to the case temperature of the output device too. Does the heatsinks of your Carbon get significantly warmer when the amp warms up? I am theorizing that if the amp has oversized heatsink that barely gets warm the offset may drift much less. But this is just a guess.

(Uncaffinated) Lemon Slice and lemon shortbread.

Yeah, Dave Grohl has to be gutted. On tour, in Columbia, do not look forward to the details surrounding this as it is hard to imagine they'll be happy.

Because, reasons. Sonic Highways Foo Fighters 2014 https://album.link/us/i/910701272 RIP - Taylor

So we had the same server as last week. This week’s attempt at “Esmé”.

I was able to bring the other channel to the same THD+N performance. While I was at it, I tried the current production low-noise JFET from Toshiba, the 2SK209. The first 2 from the cut tape matched really well at 5.9mA Idss at Vds=10V. I'm surprised that I was able to do it without using the microscope or magnifying glass (pardon the flux residue though). I guess I no longer need to pay the hefty price to get the LSK389 or the obsolete K170s. Regarding jacking up the bias of the SiC FET, it has its limits. The original bias resistors set the SiC FET G at 450*20/(175+175+20) = 24.3V to B- with a -450V supply. After adding 260k in parallel with the 175k Ohm resistor, I was able to set the G at 27V to B- with a -407V supply. Note that the VGSmax for the G2R1000MT17D and the C2M1000170D are 25V, and is 23V for the MSC750SMA170B. So I'd better dial it back a little. In normal operating conditions, the voltage on the 20k resistor will never apply entirely to the G-S. But it kind of tells me how intricate the original design was, with all corner cases considered.

My mother's maiden name is Styants, which is pretty unusual (like Samost). Because it is so strange it is easy to trace back. I've got as far as the late 1600's, but its root is the Anglo-Saxon Stigand. In fact the Archbishop of Canterbury in 1066 when William of Normandy invaded was called Stigand. But clergy back then would commonly take a wife or two, and/or other women, so who knows - I might date back to a very naughty Archbishop 960 years ago.

I’ve been driving Esmé crazy with her new name.

In a previous post I mentioned the less-than-ideal performance when Carbon is powered by a ±400V supply, and I suspected that the lower Vce on the PZTA42 is the culprit. Now it's been proven. The PZTA42 being a high voltage transistor, has a non-linear region at low Vce, as the slanted curves you can see on the upper left side. With 407V on the negative rail, the transistors on my board works at Vce=8.4V and Ic=20mA, right around the knee. The global negative feedback would have a hard time correcting that non-linearity. It also explains why some people prefer setting the Carbon at a lower current when powered with ±400V supply, as it also improves the linearity of the PZTA42, albeit to a lesser degree. I guess Kevin chose the high voltage PZTA42 to deal with the power-on transients. I have a quick and dirty fix. Just bias the SiC MOSFET a little higher to give the PZTA42 more headroom. The SiC MOSFETs are biased by two 175k and an 20k at the gate. Reducing either 175k or increasing the 20k would do. The goal is to move the PZTA42 operating point to the right, well into the constant-current region (parallel lines). I would use Vce=14 to 15V. Pushing it even higher would increase the power dissipation on the PZTA42, eat into the max output voltage swing and have diminishing return. What I did was to put a 260k resistor in parallel with one of the 175k resistors. YMMV because it has to do with the operating point of the PZTA42 in your circuit, the Vgs(th) of your SiC MOSFET, etc. After the quick fix, one of the channels now measures as good as with the ±450V supply. We can see that the max output voltage is slightly less compared to with ±450V supply. The difference is subtle with the log scale, though. Now I'm continue to work on the other channel and see if I can find something else.

I'm glad to report that both the GeneSiC G2R1000MT17D and the Microsemi MSC750SMA170B work well on the KGSSHV Carbon. The G2R1000MT17D works on the GRHV, too. The overall performance of the Carbon is stellar. It's virtually distortion-free to about 200Vrms at the output, and maintains very low distortion up till 600V!! You want the ±450V power supply for the Carbon. With ±400V I ended up with something like the following. Still not bad but not as brilliant as the curve above. I figured the PZTA42s are not quite in their linear region because of the reduced Vce. A word of caution is that both SiC MOSFETs are somewhat 'fragile' compared to the Cree/Wolfspeed C2M1000170D, especially the G2R1000MT17D. I killed a few when matching them on my curve tracer. I guess the Left-right switch on my curve tracer doesn't guarantee that S connects first, then G and then D. No more failures after I connected a 10V zener diode between G-S on the test fixture. An expensive lesson learned😅

This. I'm not a Foo fan but they are on the Howard Stern show a lot and Taylor tended to talk as much as Dave. They were just on recently to promote their goofy horror movie and he was super upbeat and joking about the ways Dave killed him and the others in the movie. ☹️

https://www.huffpost.com/entry/taylor-hawkins-death-foo-fighters_n_623e86dfe4b0e340f6a3374c RIP Taylor Hawkins, Foo Fighters drummer, at age 50. This one hurts a bit.