i_am_proteus (u/i_am_proteus)

i_am_proteus commented on Bring Back the Blue-Book Exam chronicle.com/article/bri... · Posted by u/diodorus

pragma_x · 4 days ago

Seems easy to thwart with two exam proctors, one at each end of the exam room. Hypothetically, the whole affair is going for maximum manual effort (grading), so why not double down on test-taking labor too?

i_am_proteus · 4 days ago

It's thwartable with adequate proctoring. I know about this mode because I found students doing it, and the students in question endured substantial academic consequences.

Large lectures have hundreds of students, and to properly proctor an exam for one of these classes, one needs dozens of proctors.

It can be done, but observe: for most faculty, maintaining the integrity of their course does not aid them on the path to tenure/advancement.

i_am_proteus commented on Bring Back the Blue-Book Exam chronicle.com/article/bri... · Posted by u/diodorus

refulgentis · 4 days ago

I'm curious, how is AI assistance on an in class exam even possible? I can't picture how AI changed anything from, say, post-iPhone. i.e. I expect there to be holes in security re: bathroom breaks, but even in 2006 they confiscated cell phones during exams.

I guess what I'm asking is, how did AI shift the status quo for in class exams over, say, Safari?

i_am_proteus · 4 days ago

People bring in second phones: one to have confiscated, one to use on the exam.

A common mode I have seen is phone in lap, front-facing camera ingests an exam page hung over the edge of the desk. Student then flips the page and looks down for the answer.

i_am_proteus commented on Show HN: Doxx – Terminal .docx viewer inspired by Glow github.com/bgreenwell/dox... · Posted by u/w108bmg

i_am_proteus · 11 days ago

I have noticed many nice projects built on Rust + ratatui - many thanks to the creators and mantainers.

i_am_proteus commented on Nuvistor Valves r-type.org/articles/art-1... · Posted by u/userbinator

fuzzfactor · 11 days ago

Look closer at that Twin Reverb schematic.

When you plug your guitar into input 1, its arrow contact with ground is disconnected, leaving the 1 Megohm resistor as the only direct path.

That's a million ohms "isolating" or "connecting" your sensitive guitar signal with ground, whichever way you want to look at it.

So your high-impedance guitar signal will not be all lost by finding an "easy" path to ground, and a nice strong signal appears at the input grid of one of the triode structures found within the dual-triode 7025 tube.

The 7025 was simply a 12AX7 that had been built for lower noise & microphonics, or selected for it, and given the 4-digit military-industrial tube number instead of the 12AX7 nomenclature recognized by consumers. You need low noise in the input stage more than anywhere else.

Follow your signal carefully and you will see that it has to pass through some resistance before it hits the grid, from input 1 both 68K resistors are in parallel, resulting in a 34Kohm working connection between your guitar and the grid.

Well that 34K is almost nothing compared to the megohms of internal impedance of your magnetic pickup. Once some waveforms have made it out of that highly-coiled super-long thin-ass copper wire inside the pickup, which makes your pickup have orders of magnitude more impedance ohms than its measurable DC resistance ohms, 34K is not even a speed bump.

Might as well be zero ohms and it sounds about the same but tubes kind of like a little something on that pin for stability.

Pedals can be good for more than one reason, like simple boosters that are perfectly clean and put out no distortion of their own but overdrive that input triode to complete metal mayhem, or sophisticated pre-processors with no additional gain at all. However, your signal will usually have a lot lower impedance coming out of a pedal into the amp, and so the interaction with the grid will be quite dissimilar in some ways, for better or worse.

Plus that's usually adding many more components between your instrument and that grid, and some of these solid-state components can be so tasty you don't want to do without them completely, but when you think about it, sometimes a single pedal will have more components between your guitar and that sensitive grid, than there is between that grid and the speakers. This is a legendary top pro Twin Reverb, and look how simple the rest of the vintage circuit is, before your music goes through that monster high-voltage audio transformer and hits the speakers. The tubes are doing a lot of work here.

Remember the Twin Reverb became the choice of pros and stayed that way for years before pedals were even invented.

IOW when you plug straight in is the only time you are "magnetically coupled" with the first grid, aye to the vacuum of space.

There is no further contact with what most people call "matter".

And from that point on your music is being sprayed through space, directly from your fingertips like no other way ;)

i_am_proteus · 11 days ago

Thank you for your comment. I must admit that I am baffled by it. Is this a series of general observations on the function of the Twin? It does not seem to respond to the prior discourse about 6L6GC power tubes being run above design maximum plate voltage.

Certainly it is very wonderful to observe the relative simplicity of tube amplifier schematics, which rely on a mere handful of passives for bias and tonestack, compared to solid-state amplifiers, that require complicated arrangements to provide negative feedback necessary to stabilize the transistors.

i_am_proteus commented on Derivatives, Gradients, Jacobians and Hessians blog.demofox.org/2025/08/... · Posted by u/ibobev

whatever1 · 12 days ago

I can look around me and find the minimum of anything without tracing its surface and following the gradient. I can also identify immediately global minima instead of local ones.

We all can do it in 2-3D. But our algorithms don’t do it. Even in 2D.

Sure if I was blindfolded, feeling the surface and looking for minimization direction would be the way to go. But when I see, I don’t have to.

What are we missing?

i_am_proteus · 12 days ago

Without looking up the answer (because someone has already computed this for you), how would you find the highest geographic point (highest elevation) in your country?

i_am_proteus commented on Nuvistor Valves r-type.org/articles/art-1... · Posted by u/userbinator

JKCalhoun · 12 days ago

"Valves" had always been a mystery to me. When I began to really get into electronics, vacuum tubes were a kind of distant echo from my childhood that I barely remembered. As a kid I remember staring into the back of the small B&W television we had when I was young — the insides looking to me like some kind of Things to Come cityscape in miniature — all lit with orange neon. And there too was the ubiquitous "tube tester" in the Rexall Drug Store (looking somewhat like a prop from perhaps Lost in Space).

As an adult Thomas J. Lindsay’s books on building small regenerative vacuum tube receivers caught my attention — I also got caught up in building both tube-based guitar amplifiers and hi-fi audio amplifiers. These allowed me to dive into tubes and finally learn about them — you know, posthumously as it were.

After initially thinking that tubes were probably inferior in all ways to solid-state, I came to find them to still be very capable and even arguably better — at least with regard to sound amplification. Somehow too I had imagined in my mind they were outrageously dangerous to work with — thousands of volts — and assume,ed they were fragile and quick to "burn out".

The circuit I used however never went over 300 or so volts (to be sure, you still need to be careful with these circuits in a way you may not be familiar with if Arduino circuits are all you know).

The tubes have never seemed to burn out for me — even after one or two amps have been my "daily drivers" for well over a decade (two decades?) now. Perhaps other circuits used less capable tubes or pushed them to their limits? Perhaps other enclosures like TV's did not allow adequate ventilation? I don't know.

And as for fragility — I mean they are glass, but the tubes I used in my hi-fi amps were NOS from WWII bomber radios. They seem to hold up to a good deal of bouncing around.

i_am_proteus · 12 days ago

Guitar amps that routinely blow tubes usually operate past maximum rated plate voltage. As an example, the Fender Twin Reverb[0] runs 6L6GCs[1] at 460V plate voltage, above the stated class-AB pentode max of 450V.

I've used the same tubes at a very reasonable 325V in a SET (actually single-ended pentode) hifi amp (built myself).

TV tubes would often burn out because of transients from switching channels.

[0]https://schematicheaven.net/fenderamps/twin_reverb_ab763_sch...

[1]https://frank.pocnet.net/sheets/127/6/6L6GC.pdf

i_am_proteus commented on Blue-collar jobs are gaining popularity as AI threatens office work nbcnews.com/business/busi... · Posted by u/geox

frankdorr35 · 13 days ago

Same here, however with the new meta glasses or the augmented reality glasses you're going to see people with no knowledge of our field actually troubleshooting machines with technicians remotely. They will be paid a lot less than us.

i_am_proteus · 13 days ago

I wonder who will be held at fault when the low-paid in-person troubleshooter discovers 15kV with his fingers (I do not wonder who will be killed) while his lock opens the wrong breaker.

The business is not broken and does not need "fixing."

i_am_proteus commented on Volkswagen locks horsepower behind paid subscription autoexpress.co.uk/volkswa... · Posted by u/t0bia_s

whartung · 13 days ago

I have one of these, but it’s not a Ford. It’s a BMW motorcycle.

At the time, the F-series came in the F-750 and F-850 models.

The motors are identical, the computers restrict the top end horsepower.

But, those aren’t the only differences. The 850 is more designed for off road than the 750. The bike is taller, large front wheel, spoked wheels.

I’m have the 750, the more street oriented version. But here’s the thing.

As they say in motorsports, there’s no replacement for displacement. My peak HP may be down to the 850, but I get all of the torque, which is one aspect that makes a motorcycle better to ride. Torque really helps with acceleration, and my bike will get to ludicrous speed quite handily.

Also in some jurisdictions, riders are limited by HP as to what bikes they’re allowed to ride due to tiered licensing. The 750 falls under one of those lines.

So I can’t speak to Ford, but I think the way BMW uses this in the F-series is quite reasonable on several levels.

i_am_proteus · 13 days ago

Same thing on the current F-800 and F-900: identical engine blocks, different power outputs, F-900 comes with taller suspension, spoked wheels, and so forth.

I believe part of the rationale is that Euro A2 licenses permit a "restrictor kit" to reduce motor power below 47 hp, but only if maximum horsepower is less than 94 hp (double the limit). One can buy an F-800 with a restrictor, and then remove the restrictor once one has obtained the upgraded license.

Now, looking at the motor torque and power curves, most of that extra power comes in the high RPMs. In practical riding of BMW twins, I find that I rarely place the motor into the high RPMs, because the torque curve is nice and flat and there's plenty of pull in the low range :)

i_am_proteus commented on Kodak has no plans to cease, go out of business, or file for bankruptcy kodak.com/en/company/blog... · Posted by u/whicks

PaulHoule · 14 days ago

The film business is increasingly niche.

I can’t get over how much better performing 35mm full frame mirrorless cameras are than the old film cameras. To get a shot like this

https://mastodon.social/@UP8/114401857009398302

with film I would have needed a medium format camera and tripod, today it is an easy handheld shot you can do spontaneously with a travel lens that goes from 28-200mm. I can go to a soccer or basketball game and shoot bursts, come back with 3000 photos and catch things like two guys tries to head the ball at the same time

https://mastodon.social/@UP8/113240678816336189

… and I can afford to do it!

i_am_proteus · 14 days ago

If you're interested, hunt around for an EOS-1 or 1N - it's a 35mm film camera with pretty fast autofocus that can use contemporary Canon EF-mount lenses. (Canon still sells the cameras and lenses, although they're being phased out in favor of RF). Load Portra 400 and shoot in good light, and you might be surprised.

i_am_proteus commented on Kodak has no plans to cease, go out of business, or file for bankruptcy kodak.com/en/company/blog... · Posted by u/whicks

porphyra · 14 days ago

Fujifilm's digital cameras are also doing great these days in a somewhat surprising comeback.

i_am_proteus · 14 days ago

Perhaps not so surprising: Fuji was producing excellent film cameras and lenses in the 1980s and 1990s, whereas Kodak was not.